NEWS

20/01/2009
THE FAILURE RATES OF SURFACE HIP REPLACEMENTS – THE REALITY

There is still a lot of “rumors” about the results of surface hip results. Whereas some surgeons argue that the surface hip replacements have results equally good or better than total hips, other authors say that excellent results are mainly published by developers of surface hip models and that results published by National Hip Registers demonstrate unacceptably high rates of failures (Spierings 2008).

Diagram: Failure rates of SHR
The picture displays the percentage of failures in the seven statistics of surface hip replacement (SHR) published during the last three years. Every bar depicts the percentage of surface hips that failed during. Patients in these statistics were followed up for 4 – 7 years after surgery. The failure rate varied from 2% to 6% failed surface hips during this follow up time.

You may see that the highest failure rate (6 %, red bar) was published by a surgeon (Amstutz 2007) who collaborated closely with the manufacturer on the special model of SHR model (Conserve Plus).

The yellow bars in the middle of the diagram are results published by the Australian and the English National Hip Registries. The one stated 4.4 %, the other one 4.6% of failures. These failure rates thus lie in the middle, scarcely could they be considered “unacceptably high”.

The two statistics with the lowest failure rates (2% failures in each statistics) were published by independent surgeon, the follow up was in both statistics five years.

Information for you: The published results of failure rates after surface hip replacements show low rates of failures, deep under the benchmark (max 1% failures annually).

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References:

Amstutz H. et al. Resurfacing THR for patients younger than 50 years. Clin Orthop 2007; 460: 159 -64
P. Spierings: Hip resurfacing: expectations and limitations. Acta Orthopaedica 2008; 79: 727-30.

15/01/2009

SURFACE HIP REPLACEMENTS – GOOD OR BAD?

The last 2008 issue of the renowned Acta Orthopaedica presents a series of articles criticizing the performance of surface hip replacement devices.

The Netherlander surgeon P. T. J. Spierings presents a review entitled “Hip resurfacing: expectations and limitations” (Spierings 2008). He maintains that there are several areas where the SHR (Surface Hip Replacements) perform worse than expected. Here follow some of the critical points.

Surface hip replacement (SHR) is a difficult surgery even for experienced surgeons; easy resurfacing arthroplasty does not exist. In particular, positioning of SHR components is critical for the future success of the resurfacing surgery. To achieve the right position the surgeons use complicated apparatuses; command of these apparatuses need to be learned, and the knowledge retained by repeated use of apparatuses. It follows that SHR is an operation to be carried out by specialized surgeons with high annual volume of SHR operations.

Picture: Femoral head surrounded by instruments to find the right plane for the chamfering of the femoral head. Really, this is not easy surgery. (Amstutz 2005)

SHR is not a surgery for everybody. Young, active men with osteoarthritis of the hip joint have the best bone stock and as such are the best candidates for treatment with SHR. At the same time these patients have the worst results among the patients operated on with total hip replacement. It would seem that this patient group would perform best with SHR. Unfortunately, about 50% of young active men with hip osteoarthritis are still unsuitable for SHR. Their femoral heads and necks have defects, cysts, and deformations that make the result of SHR unpredictable.

Women in and after menopause age have often osteoporotic skeletons (skeletons with lack of bone tissue) and are not candidates for SHR. Even young women with good skeleton are not good candidates for SHR. There is always risk that these patient will after menopause develop osteoporosis of the whole skeleton, inclusive of the hip joint, with risk for fracture of the surface replaced hip skeleton.

The surface replacement device creates “stress shielding effect” (see the chapter Function of THP / stress shielding) which is well seen on the x-ray pictures of the femoral neck under the replaced femoral head. The femoral neck becomes thinner (surgeons speak about “neck thinning”); this effect is observed in about every third patient operated on with SHR. In combination with other factors, the thinning of femoral neck can eventually result in femoral neck fracture.

Although not mentioned, resurfacing arthroplasty produces hip joints with lesser range of movement than range of movement produced by total hip replacement. These results are based mainly on theoretical and laboratory studies, but are seldom if ever found in live patients evaluation. This may be so because the studies comparing the results of SHR and THR are very rare and incomplete.

The failure rates of SHR vary. Whereas failure rates published by the surgeons who developed the individual SHR models are usually very low, the failure rates published by other orthopaedic surgeons are higher as are also the rates published by National Registers. These latter statistics also show that the risk for a patient operated on with SHR to fail during the early postoperative period (1-4 years) is 1.4 times higher than for a patient operated on with a total hip replacement.

Information for you: It you think that you are a candidate for a surface hip replacement you should carefully discuss the advantages and risks of this type of surgery with your surgeon, who should have considerable experience with this type of operation. Read also the chapter Surface hip replacement.

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References:

P. Spierings: Hip resurfacing: expectations and limitations. Acta Orthopaedica 2008; 79: 727-30.

December 2008

18/12/ 2008

INTERNET ACCESS PRODUCE MISINFORMED PATIENTS – SAY SOME SURGEONS

Although many patients find useful information on the Internet, 80% of recently surveyed USA orthopaedic surgeons said that their patients get wrong information from Internet patient information sites. Not only that, 35% of surveyed surgeons maintained that misinformed patients needed more of their precious office time because it was difficult to iron out this misinformation from the patient’s mind.

Such surveys express always the opinions rather than facts. Practicing orthopedic surgeons in the USA obviously do not like patient information sites, which does not prevent many of them to have own information site. Often such information site is rather a site advertising what kind of surgery the surgeon is carrying out, but seldom there is specific information who is a candidate for such surgery. I have as yet to find a site where the advertising surgeon publish also his /her operation results, but for the Belgian surgeon Doctor DeSmeet.

There are, however, other orthopaedic surgeons in the USA who think that good Internet information sites are very useful for their patients. One of them is Professor David Hungerford, known for his research on osteonecrosis of the hip joint.

On the International Meeting on Current Concepts in Joint Replacement in December 2008 Professor Hungerford said that Internet patient information should be more specific and presented so that the patient can understand it.

He also presented an example of a misinformed patient. A typical case is the patient asking to have a ceramic on ceramic total hip replacement carried out "as Jack Nicklaus had it".

These patients started to appear after the Stryker company embarked an a huge advertising campaign showing Jack Nicklaus who continues to play golf after a ceramic on ceramic total hip replacement (Model Stryker).

It is the surgeon’s obligation to explain to the patient that the ceramic total hip, which was successful in Jack Nicklaus case, may not be a good choice for his patient. The surgeon should explain that the right question for the patient to ask is:: Which total hip model is the best for me, your patient?

One should simply look on the Internet patient information from the patient’s perspective. Unfortunately such information is not yet available for total hip patients. British hernia surgeons, however, studied this issue.

Two patient groups were prepared to undergo hernia surgery. One group read selected Internet patient information sites on hernia surgery before their consultation with the surgeon and subsequent operation; the other group had no such Internet information.

80 % of patients who read the Internet sites were satisfied with the surgery, compared to only 45% satisfied patients in a group that did not have access to Internet information. These figures show the usefulness of Internet patient information. But as yet, in spite of many irrelevant “surveys” there are no such studies examining the effect of Internet information on patients to be operated on with total hip replacement.

Information to you:

Internet information provides you with information. But you should know that much of the information on Internet has, however, low or no information value. There are ways to choose Internet sites with rather good information that you may use in your discussion with the surgeon. See also the chapter: Information on Internet .

The most nonsense answer to a patient complaining of pain in the operated total hip / knee is: “Your x-ray pictures are normal”. If only Internet information could eradicate this nonsense answer much will be done.

16/12/2008

BILATERAL SIMULTANEOUS TOTAL HIP REPLACEMENT – IS IT SAFE?

Yes say the British surgeons who studied the published statistics (Tsiridis 2008). The authors studied and evaluated all published statistics and found reliable reports on 2800 such simultaneous operations.

Depending on the diagnosis, about 10 to 20% of all patients may have severe engagement of both hip joints that need replacement with total hip, For these patients there arise a problem: should they have replacement of both hip joints done simultaneously, that means during one narcosis session? Or should the surgeon replace first one hip joint and then wait with the operation of the second hip some weeks or months until I recover from the first surgery – so called staged operation?

Bilateral simultaneous total hip replacement was first reported by the well known English hip surgeon sir John Charnley in 1971. Since then the surgeons disputed whether the simultaneous procedure entails bigger risks for the patient than the staged procedure.

The English surgeons found that the simultaneous procedure is safe provided that the patient is healthy. Thus all potential candidates for bilateral simultaneous THR should undergo a detailed anaesthetic assessment preoperatively, and patients with ASA grades 1 and 2 are the safest for the simultaneous procedure. (ASA grades is an evaluation procedure for evaluating operation risks developed by American anaesthesiologists) .

It follows that elderly patients are not excluded from bilateral simultaneous THR if they are otherwise healthy, as age is not per se a contraindication.

The risk of DVT or pulmonary embolism, the risk of dislocation is not

increased in bilateral simultaneous THR, provided that appropriate prophylactic measures are taken.

The overall surgical time is not different between bilateral simultaneous THR and staged THR and the length of hospital stay is shorter after a bilateral simultaneous THR.

Functional outcomes are similar after bilateral simultaneous THR and staged THR.

Information for you: This article present a very well assessed evidence that bilateral simultaneous total hip replacement is safe for healthy patients. Higher blood transfusion requirements are expected following bilateral simultaneous THR than following staged THR or unilateral THR, because of total cumulative loss in one sitting is greater.

The authors therefore strongly suggest that autologous blood transfusion, whether by pre-operative donation or by intraoperative blood salvage, be considered. The authors also recommend that bilateral simultaneous THR be ideally undertaken in tertiary referral hospitals experienced in major hip surgery.

See also the chapter Candidate for simultaneous bilateral total hip

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References:

Tsiridis E. et al.: The safety and efficacy of bilateral simultaneous total hip replacement. J Bone Joint Surg-Br 2008; 90-B: 1005 -15

10/12/2008

COBALT POISONING IN A PATIENT WITH FAILED CERAMIC BALL COMPONENT

Toxic metal blood levels may occur in failed total hips, even those where one of the bearing surfaces is polyethylene. The following case, published by German surgeons shows the less known risks of ceramic total hips (Oldenburg 2008).

A 55-year-old man had a well functioning total hip (ceramic femoral ball articulating with polyethylene cup). After a fall, the ceramic head broke into several pieces (burst fracture). Revision operation followed. The surgeon removed the fragments of the broken femoral ball and then replaced the ceramic ball with a conventional metal ball made from the cobalt chrome alloy. Also the polyethylene cup was replaced.

Three months after this revision operation, the so far healthy patient complained over general pain, fatigues, heart, and neurological symptoms. Clinical examination revealed signs of heart muscle damage, damage of peripheral nerves, and diminished function of the thyroid gland – all signs of poisoning by cobalt. Blood tests rightly discovered toxic blood levels of the cobalt and one made the diagnosis of cobalt poisoning from wear particles coming from the metallic femoral ball.

At a new revision operation the surgeon discovered severely scraped femoral ball damaged by the hard ceramic particles that were “overlooked” at the previous revision operation. Soft tissues around the total hip were colored black by massive deposition of cobalt and chrome wear particles.

The surgeon removed the now all soft tissues with deposed metal and with left ceramic particles, replaced the damaged femoral ball and also the cup for second time.

After this second revision operation, the toxic blood metal levels diminished and the patient’s signs of intoxication by cobalt successively vanished.

Information for you:

Fracture of ceramic total hip, may it be ceramic ball or ceramic liner, has many sinister consequences. This report does not tell how long the follow up was after the second revision operation. From larger statistics it appears that some fracture of ceramic balls (actually 8% of them) need two and more revision operations.

The core of the problem is the character of the ceramic ball fracture, It produces small hard fragments that stay in the tissues around the failed ceramic total hip. Unless the surgeon does really a painstaking removal of really all soft tissues around the failed ceramic total hip at the revision operation, the mixture of ceramic particles with soft tissues make a brushing paste that really destructs every metallic object – even a hard cobalt chrome made femoral ball (See pictures in Fracture ceramic ball). This and rare other similar cases are the reason why many surgeons are still hesitating to recommend ceramic total hips for active young patients.

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References:

Oldenburg M, et al.: Severe Cobalt Intoxication Due to Prosthesis Wear in Repeated Total Hip Arthroplasty. J Arthroplasty. 2008 Oct 1. [Epub ahead of print]

02/12/2008

CERAMIC ON CERAMI TOTAL HIPS – 8 YEARS RESULTS

Modern ceramic on ceramic total hips really do not have a long history. Still the majority of reports describe less than ten years experience with them. One of the surgeons who early on started to use the ceramic on ceramic total hips now publish the results of his 8 year observations on 452 patient who totally had 475 total hips implanted. These were young patients (mean age 53 years) who have the replacement done mostly (in 82%) for osteoarthritis.

During these 8 years, only 9 patients (2.4%) required revision operation of their ceramic total hips; none revision, however, was done for loosening of the total hip. 0.5% of ceramic cup liners fractured, a disquieting figure. Also 0.5% of all ceramic total hip produced “transient squeaking sounds”; one of these patients required operation for painful encroachment of the iliopsoas muscle.

Information for you: The results of these ceramic on ceramic total hips are better than results with conventional metal on polyethylene total hips. The only disquieting fact are the 0.5% fractures of the ceramic cup liner, which is above the reported experience in other series.

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References:

Capello WN,et al: Ceramic-on-ceramic total hip arthroplasty: update. J Arthroplasty. 2008 Oct;23(7 Suppl):39-43

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01/ 12/2008

A NEW CERAMIC MATERIAL FOR TOTAL HIPS

The alumina ceramic total hips have already a low wear but the scientists are studying new material to find as yet better and less wear sensitive materials.

One such material is a mixture of alumina and zirconia ceramic, a mixture of crystals of aluminum and zirconium oxides.

In laboratory studies this new ceramic has a very low wear rate, 1.5 cu mm per one million “steps” on hip simulator. This is substantially lower wear rate than the wear rates of zirconia ceramic but even lover then wear rates of alumina ceramic.

As yet I did not find any total hip model which would use this new kind of ceramic but it will certainly come, because with this kind of new ceramic the size of the femoral ball does not influence the wear rate. Femoral head components made from this material with 28 mm diameter had equal wear rate as the ball with 36 mm diameter.

Information for you: this material probably would be used for bearing surface of total hip joint destined for the young and active patients. It is also interesting that the zirconia ceramic itself (with 4% admixture of yttrium) performed so badly in ceramic femoral head components articulating with polyethylene cup, zirconia as admixture to alumina ceramic functions on the other hand performs so well in a wholly ceramic on ceramic total hip.

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References:

I. C. Clarke, et al.:Ceramics in Orthopaedics. Bioceramics and Alternative Bearings in Joint Arthroplasty. 11^th BIOLOX® Symposium Rome, June 30 – July 1, 2006 Proceedings

November 2008

04/11/2008

WHY DO THE METAL BLOOD LEVELS IN PATIENTS WITH SURFACE HIP REPLACEMENTS DIFFER SO MUCH

Practically all patients with surface hip replacement devices have high blood levels of cobalt and chrome metals. These metals constitute a major part of the metal alloy from which the resurfacing devices are made.

But the individual levels of these metals vary very much – in some patients the levels are elevated only two three times and in other patients the elevation may be hundred fold.

A joint group of British and Belgian surgeons has found one of the important factors that influence the blood level of these metals (De Haan 2008). It is the position of the cup component.

They examined metal blood levels in 214 patients with surface hip replacement operations up to 3 years after surgery. Patients who have had a too steep position of the cup component have had significantly higher levels of cobalt and chrome in their blood, especially if the component were of smaller size. This happened especially in smaller female patients.

Picture: The picture shows inclination angle on an operation model - how an artist sees it.

The steepness was measured on the x-ray pictures and the surgeons call it “inclination angle”. It should be less than 55 degrees.

On the other hand, patients’ physical activity had no influence on the metal blood levels.

Information for you: It seems that a surgeon should be able to place the cup component in just “the right position”, which is an inclination less than 55 degrees, to prevent too much elevated metal blood levels..

However, this inclination angle is measured on x-ray pictures. Only the experienced surgeon can imagine how he / she position the cup component in the patient’s hip on the operation table to achieve the right position later on x-ray pictures. The authors give no instruction how to do it but it seems that experience would help.

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References:

DeHaan R et al: Correlation between inclination of the acetabular component and metal ion levels in metal-in-metal hip resurfacing. J Bone Joint Surg-Br 2008; 90-B: 1291 - 7

25/10/2008

25 YEAR SURVIVAL OF POLYETHYLENE TOTAL HIP – OSTEOLYSIS THE MAIN CAUSE OF FAILURE

Long term observations of survival of total hips are rare and suffer often one fault – the observed total hip model is not longer on the market. German surgeons published recently statistics about survival of a cementless total hip model that, although produced by a smaller Swiss manufacturer (Mathys Ltd), is still on the market (Ihle 2008).

The described total hip model had an interesting cup component (RM acetabular component TM). It is made of massive polyethylene block. On the outside of the component is a thin layer of pure titanium particles. These particles are heat pressed directly into the surface of the polyethylene. Theoretically, the titanium particles would influence ingrowth of bone tissue into the surface of the cup, but these particles would not influence the elasticity of the cup as occurs in metal backed acetabular components.

The German authors found that 80% of the operated on total hip model survived 20 years. Especially, the cup component was successful as 83% of all cups survived 20 years.

These figures comply with the benchmarks for successful total hips (max 1% failures annually).

The interesting observations are the figures for the rates of the three important causes of failures and when they occurred. The infections (2%) occurred during the early postoperative years (up to 4 years), whereas the aseptic loosening (5%) and osteolysis (7.5%) occurred later on ( after 4^th operative year.

The rate of osteolysis that necessitated revision operation is remarkably high, but then the cup component was fabricated from polyethylene that was sterilized by gamma irradiation in the air. This old sterilization technique is known to change the polyethylene structure (production of free radicals) that makes the irradiated polyethylene more wear prone.

Information for you:

This report is interesting mainly because it demonstrates that osteolysis and loosening are late complications. It follows that a statistics that followed the patients with total hip operations five years and less are unreliable, they cannot tell how many of these patients’ hips would become loose or would develop osteolysis.

Remember that most statistics concerned with hip resurfacing have follow up period just five years and less!.

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References:

Ihle M et al: The results of titanium –coated RM acetabular component at 20 years. J Bone Joint Surg-Br 2008; 90-B: 1284- 90

22/10/2008

OBESE PATIENTS AT GREATER RISK OF TOTAL KNEE FAILURE

There is still a discussion whether overweight patients are at greater risk for aseptic loosening of total knees. One theory supposes that loosening is caused by early micromotion of the implanted total knee device that never had occasion to be ingrown by the patient’s bone tissue. According to this theory, overweight patients should subject their total knees for overload right from the first postoperative day. The overload then will cause early instability of the total knee device and later on aseptic loosening.

The other theory of total knee loosening assumes that the loosening has a biological cause, the wear particles from the total knee surfaces causing inflammatory reaction that destructs the fixation of the total knee device to the patient’s skeleton.

American surgeons at the Center for Hip and Knee Surgery, Mooresville, Indiana, studied the relation between the patient’s body mass index and loosening of a total knee device (AGC total knee model) (Berend 2008) . In a group of 6500 total knee operation they found that patients with greater body mass index (BMI) were at significantly greater risk of loosening if they had a small model of the total knee implanted.( See also the chapter Obesity details).

This sounds more logical (although simple logic is rare in the science of total joints), because greater body weight acting on a smaller total knee model produces higher stresses per unit of square area. Thus overweight patients with small total knee devices had very high stresses on their total knee devices.

The authors could strengthen the hypothesis that increased stresses are behind the loosening of total knees in obese patients by sophisticated x-ray measurements of the early micromotion of the implanted total knees. They found that the micromotion of the total knee early after surgery increased in obese patients and was greatest in obese patients who had implanted relatively small total knee devices.

These measurements, done in totally 80 total knees, demonstrated that in obese with small device the total knee was unstable already early after the surgery and this instability increased successively until there developed a full scale loosening and the patient needed a revision operation.

Information for you: This is new information in a study that, however, is not fully statistically correct. Other similar studies could not prove causal connection between overweight and increased rates of total knee loosening. But even these studies demonstrated that overweight patients had longer and more difficult rehabilitation period after total knee replacement operation. Thus, if you are overweight and if you can try to go down with your body weight. If you believe that it will be easier after surgery, you are wrong!

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References:

Berend ME, et al.: . Implant migration and failure in total knee arthroplasty is related to body mass index and tibial component size. J Arthroplasty. 2008; 23(Suppl 1):104-9.

20/10/2008

METAL-ON-METAL TOTAL HIPS – TEN YEARS RESULTS OF A TOTAL HIP THAT CAUSED BANKRUPTCY OF SULZER’S COMPANY

Metal-on-metal total hips were reintroduced on the European market by the (late) Swiss surgeon Bernhard Weber in 1988. The Swiss manufacturer (Sulzer Orthopaedics Inc.) developed a new cobalt chrome alloy and the new total hip system got the name Metasul TM. In the year 2000 claimed the manufacturer’s website (www.metasul) that over 100 000 total hip models were sold.

Picture of the Metasul total hip model. Although the manufacturer promised "lifetime warranty" of this total hip model, the "improved product" failed catastrophically later on

Clinical reports published about this total hip model were observation on small patient populations (less than 100 operations) done under short follow up time (5 years).

Eventually, the manufacture of the total hip model was changed and the changed total hip model (cup component) got the name InterOp TM. This change of manufacturing process left a lot of highly toxic cleaning liquid on the surface of the finished product. The rests of the cleaning liquid produced intesive soft tissue inflammation and brought in catastrophic failure rates of the product. This all together led to bankruptcy of the Sulzer’s Company.

How good or bad was the original Sulzer’s Metasul total hip?

English surgeons published recently a statistics of ten years results of Metasul total hips (Eswaramoorthy 2008).

From this statistics, that was also done on a rather small patient sample (100 patients with 104 total hip operations) it appears that this total hip model performed rather well. Under ten years of follow up there appeared “only” 7% complications that needed revision operation. The survival was 94% under this time period. These results fulfill the benchmarks of ten year results stated by the British NICE authorities with good measure.

Was it unfortunately that a "slipshod manufacturing detail" removed an actually good total hip model from the market? I am not so sure. This total hip model had an obvious flaw. It caused something what is called in the report "unexplained pain".

Out of the 7% revision operations, 4% were done for this “unexplained pain”. Closer examination of the tissues removed at revision operation of these patients discovered signs of an allergic reaction, probably to the metallic wear particles.

Information for you: This is a rather historical study. The Sulzer Company was bought by Zimmer, Inc. that continues with the Sulzer's MetasulTM total hip program, But the cup of the new Zimmer MetasulTM total hip is no longer a cementable polyethylene cup with metallic inlay. Now it is a 4 mm thin all-metal cup that has room for very large femoral heads (>50 mm). And we have equally few information about these new Zimmer MetasulTM cups as we have had about the "old" Sulzer ones. A mess? I agree.

The "old" MetasulTM total hip model studied in this report is no longer available on the market. But this study is valuable because it demonstrates a problem with all metal on metal total hips. The wear particles from their surfaces may cause allergic reaction in certain patients. Although not a very frequent complication it is sufficiently serious to be considered be the future candidates of total hip replacement.

This allergic reaction occurs in about 1 – 4 % of all patients with all forms of metal on metal hip replacements, total as well as surface replacements.

And the biggest problem is that the surgeons do not know any method as yet to discover which patients would develop this allergic reaction after the surgery. Zimmer's own specialist on metal on metal total hips, Dr L. Dorr, says that patients with suspect or known allergy to metals that are part of the Metasul alloy (chrome, cobalt, nickel) should not have a metal on metal total hip. (http://www.metalsul.zimmer.com). But even patients with no known previous metal allergy may (and do) develop the allergy after implantation of metal on metal hip replacement devices.

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References:

V. Eswaramoorthy et al. : The Metasul metal-on-metal articulation in primary total hip replacement. CLINICAL AND RADIOLOGICAL RESULTS AT TEN YEARS. Journal of Bone and Joint Surgery - British Volume, Vol 90-B: 1278-1283

10/10/2008

EARLY FAILURES OF SURFACE REPLACEMENT TOTAL HIPS –LEARNING CURVE PLAYS A ROLE

There are a few independent statistics about the results of surface hip replacement. The most extensive of them, the Australian National Register, demonstrated that there is a relatively high rate of failures of surface hip replacement early on after the surgery.

A group of Canadian and Korean surgeons studied what causes these early failures to occur (Kim 2008).

In a multicenter statistics these surgeons followed 200 surface replacement patients for an average period of 30 months. They found that 7% of these patients needed revision operation. Interestingly, two thirds of all failures (5%) of failures were caused by early loosening of the cup component, whereas only one third ( 2% ) were caused by fractures of the neck (collum) of the thigh bone. When studying the risk factors for failure the authors noted that "learning curve was a factor in these cup failures”.

In another similar report from Germany, 40% of early failures of hip surface replacements occurred after operation done by surgeons who had only short experience with this operation (Morlock 2008).

Information for you. As in all surgery, experience makes the master. When contemplating the technically demanding surface hip replacement, seek a surgeon with good experience with this technique. That means at least > 50 such operations done already and continuing with similar amounts of annually operations. Of course also a surgeons who had gone one of the many learning courses arranged by the big manufacturers.

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References:

Kim PR, et al: Causes of early failure in a multicenter clinical trial of hip resurfacing. J Arthroplasty. 2008 Sep;23(6 Suppl 1):44-9.

Morlock MM, et al: Modes of implant failure after hip resurfacing: morphological and wear analysis of 267 retrieval specimens J Bone Joint Surg Am. 2008 Aug;90 Suppl 3:89-95.

05/10/2008

HOW MANY IN HOSPITAL COMPLICATIONS AFTER TOTAL HIP AND TOTAL KNEE SURGERY

Total hip and total knee replacement surgery is a safe procedure, believe the surgeons, so that the patients are now sent home early in belief that any early complication cannot happen.

Surgeons at Rothman Institute of Orthopaedic (Philadelphia, PA, USA) decided to look how many early postoperative complications happen when the patient is still in the hospital (Pulido 2008).

They studied 15383 patients operated on with total hip and total knee replacement. In these patients occurred totally 0.16% postoperative deaths and 3.2% life threatening complications. The most frequent among them were: pulmonary emboli (1%), heart failure (0.6%), and heart infarct (0.2%).

Obviously, total joint arthroplasty, despite its success, can be associated with rare serious and life-threatening complications. More prone to these complications are aged patients (>70 years), patients with bilateral simultaneous operations, and patients with difficult long lasting revision operations.

Yet, in more than half of all studied patients no obvious risk factors were found preoperatively that might predict the occurrence of some of these complications.

Information for you.

The total hip and total knee are really safe procedures and these figures should not deter you from a planned surgery. On the other hand, these figures should inform you that total joint replacement is a “big surgery” that has a definitive but a small risk. Moreover, the majority of the above complications was successfully treated and did not left any lasting symptoms.

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References:

Pulido L. et al: In hospital complications after total joint arthroplasty. J Arthroplasty. 2008 Sep;23 (Suppl 1):139-45.

01/10/2008

HIGH-DEMAND SPORTS AFTER TOTAL KNEE REPLACEMENT

It is a generally held rule that patients with total knee replacement should avoid sports that place high loads on their totally replaced knee joint. Yet, the total knee replacement is done on successively younger patients and many of these young patients sometimes wish to participate in high impact sports. What happens when patients with total knee replacement neglect the surgeon’s recommendation and do participate in high impact sports?

American surgeons at Rubin Institute for Advanced Orthopaedic, Baltimore, Maryland, USA studied the clinical and radiographic results of 31 patients (33 knees) who participated in high-impact sports on average 4 times per week including jogging, downhill skiing, singles tennis, racquetball, squash, and basketball (Mont 2008). The minimal length of follow up was 4 years.

32 of these 33 replaced knees had successful clinical and radiographic outcomes. Overall satisfaction was a mean was very high ( 9.1 points on a scale of 0 to 10 points). These results indicate that some patients will participate in high-impact sports and enjoy excellent clinical outcomes at a minimum 4 years after surgery.

Information for you: You should consider this report rather than curiosity that recommendation. The follow up applies to only a very small patient group and there is no control group for comparison.

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Reference:

Mont MA, et al: High-impact sports after total knee arthroplasty. J Arthroplasty. 2008 23(6 Suppl 1):80-4

September 2008

30/09/2008

PATIENTS WITH DIABETES AT GREATER RISK FOR CERTAIN COMPLICATIONS AFTER TOTAL HIP AND TOTAL KNEE SURGERY.

There is still disagreement whether patients with diabetes have greater risk for immediate complication following primary total hip (THR) and total knee replacement (TKR). American surgeons used the large statistic database Nationwide Inpatient Sample to find an answer (Bolognesi 2008).

Among 751 340 THR and TKR operations done between 1988 to 2003, they found 8.55% patients with diabetes mellitus.

Patients with diabetes had longer hospital stay, greater risk for lung inflammation and stroke in the immediate postoperative period compared with patients without diabetes.

Information for you: All such large statistics must be assessed cautiously because they mix patients with different other risks. Yet, this statistics shows that patients with diabetes should have their disease well stabilized before they attempt the total joint replacement operation. This is only way hopw diminish the risk for immediate postoperative complications associated with diabetes.

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Reference: : Bolognesi MP et al.: The impact of diabetes on perioperative patient outcomes after total hip and total knee arthroplasty in the United States. J Arthroplasty. 2008; 23(6 Suppl 1):92-8.

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28/09/2008

TEN YEAR RESULTS BETTER FOR TOTAL THAN FOR PARTIAL (UNICOMPARTMENTAL) KNEE REPLACEMENTS

When the patient has only one part of his/ her knee joint destroyed by osteoarthritis, why replace the whole knee joint when there are artificial knee joint devices suitable for replacement of only one part of the knee joint. These devices are called unicompartmental knee replacement devices (UKR). See more in the chapter Outline total knee / Unicompartmental knee replacement.

About 25% of all patients with osteoarthritis of the knee joint has the wear out process limited only to the inside space (compartment) of the knee and these patients would be ideal candidates for replacement with UKR. Yet surgeons are divided whether these patients should have only this inner knee compartment replaced or whether they should always have the whole knee replaced with the total knee device.

The reason is that in some reports the results with UKR are worse than results with total knee replacement (TKR).

One such statistics is the report from the Finland’s national total knee register (Koskinen 2008). The authors followed patients with who had either TKR or UKR done since 1980 and were registered in the National Register..

The measure of success was the ten year survival of the replacement device in place since operation. The patients were divided in two groups depending on the time when the operation was done. One group was operated on between 1980 through to 1987 and the second group was operated on from 1988 through to 1995.

Picture: Bar diagram of the ten year survival of unicompartemental knee arthroplasty (UCA) and total knee arthroplasty (TKA) from the Finnish National Total Knee Registry. The blue bars represent the ten year survival percentage of UKR and the orange bars represent the ten year survival percentage of TKR.
Ten year survival shown for patients operated on between 1980 to 1987 (80-87) and for patients operated on between 1988 to 1995 (88-95)

As the diagram demonstrates the percentage of UKR replacements that survived ten year since operation was clearly lower compared with patients who had the whole knee joint replaced (TKR).

Moreover, the success rate of UKR diminished with introduction of new types of UKA devices. From the UKR operarated on in the early period (years 1980-87) 83% survived ten years whereas only 72% (!) of patients operated on with UKR in the later period (1988-95) survived ten years.

During these two periods the TKA showed a slight improvement of results (87% of patients operated on during 1980-87 survived compared with 89% of patients operated on 1988-95.)

One would suppose that the results of UKA operation would improve with time as surgeons were mastering the technique. But in Finland the opposite occurred.

Closer analysis revealed, however, that most affected by bad results was the Oxford unicompartmental knee replacement model. This model is the most technically demanding unicomapartmental knee replacement model; it was introduced in Finland during the second studied period (1988-95).

The English surgeons who developed this knee model published very good results achieved with this UKR devive. Experience from England demonstrated, however, also that surgeons operating on unicompatmental knee replacement need a relatively long training (“long learning curve”) to achieve good results. Moreover, the surgeon operating on this UKR model must perform a certain annual amount of operations (about 50) to retain the operation skill.

Finnish surgeons operate on annually about 400 unicompartmental Oxford knee replacements, divided among 30 hospitals. That means only 13 Oxford UKR done annually in one hospital.

The authors say that such “decentralization” of UKR on so many hospitals “do not lead to any good results”. A typical understatement.

Information for you: The main cause of bad results of UKR in this statistics is the low operation experience of Finish surgeons doing this technically demanding surgery. If you should choose (with you surgeon) this type of knee replacement device ask, please, your surgeon what experience he /she has with this type of knee replacement surgery.

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Reference: Koskinen E. et al: Comparison of survival and cost-effectiveness between unicondylar arthroplasty and total knee arthroplasty…… Acta Orthopaedica 2008; 79: 499 - 507

20/09/2008

EXCELLENT RESULTS OF SURFACE HIP REPLACEMENT – NO MATTER WHAT SURGICAL APPROACH ONE USES

There is still discussion whether certain approaches to the hip joint produce better results than other ones (see also the chapter Total hip operation / Approaches to the hip). This question seems to be of interest for certain patients and surgeons too.

British surgeons working at Royal Orthopaedic Hospital, Birmingham, UK, studied whether patients operated on with posterolateral surgical approach had more postoperative complications than patients who had their surface replacement done by direct lateral approach (McBryde).

The authors studied 790 patients who had totally 909 surface hip replacement done, the majority of the operations (777) were done by a posterolateral approach, the rest by a direct lateral approach. There were no differences between the two approaches for postoperative complications, additional surgery, or implant survival. The 8-year survival rate was almost equal for both groups (97.9% for direct lateral, and 97.2% for posterolatral approach).

Information for you: The most important information emerging from this report is the very high rate of surface replaced hips that survived 8 years after surgery – 97% irrespective of the surgical approach. This statistics is thus a further proof that surface replacement surgery (in carefully chosen patients) is a reliable treatment alternative for patients with hip joint ailment.

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Reference:

McBryde CW et al : The Influence of Surgical Approach on Outcome in Birmingham Hip Resurfacing. Clin Orthop Relat Res. 2008 [Epub ahead of print]

16/09/2008

PAINFUL METAL-METAL TOTAL HIP AND NORMAL X-RAY PICTURES

Metal on metal total hips are still controversial because they produce high blood levels of metals (cobalt, chrome). Moreover, in some patients they also produce early postoperative pain that the surgeon has a difficulty to explain.

A group of British radiologists studied a group of patients with early pain after metal-metal total hip replacement (Toms 2008). These patients had a normal x-ray picture. Because of continuing pain, these patients had done a MRI examination at an average 35 months after surgery. This examination discovered several “abnormalities”: collection of fluid around the total hip, dead muscle and bone tissues, and damages to muscle attachments.

Subsequent revision operation confirmed these findings.

Information to you: The metal-metal total hips seem to have some unexplained and unexpected complications, mainly specific inflammation features. Production of large sacs filled with inflammation fluid around a metal-metal total hip has been described repeatedly and is a risk that must be considered when deciding which total (and surface!) hip model to choose.

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Reference:

Toms AP et al: MRI of early symptomatic metal-on-metal total hip arthroplasty: a retrospective review of radiological findings in 20 hips. Clin Radiol. 2008 Jan;63(1):49-58. Epub 2007 Oct 24.

14/09/2008

HOW OFTEN DISLOCATE CERAMIC ON CERAMIC TOTAL HIPS?

Modern ceramic total hips have very low risk of fracture of the ceramic components so that the patients should not fear fracture of one of their ceramic components. But other fears emerged. One is the “squeaking sound” that some patients experience, whose cause and importance is not yet clear.

Another fear, based on some laboratory tests intimates that ceramic total hips are intrinsically less stable and would dislocate more easily. This may be an argument against their use in young, active patients.

Surgeons at Rothman Institute, Philadelphia, PA, thus studied the dislocation rate of 1653 ceramic total hips operated on their institution and three other clinics. The dislocation rate was 1.1% in patients operated during nine year period with cera,ic on ceramic total hips. All but one dislocation were treated successfully with closed reduction under anesthesia only.

Information for you: Although the rate of 1.1% dislocations after ceramic total hip replacement may seem too high to you, it is in par with the dislocation rates after total hip replacements with other total hip models (metal on metal, polyethylene on metal). The very low wear rate of ceramic total hip fractures coupled with “normal” rate of dislocations thus makes good argument for the use of ceramic total hips in young active patients.

: ____________________________________________

Reference:

Colwell CW Jr, et al.: Ceramic-on-Ceramic Total Hip Arthroplasty Early Dislocation Rate. Clin Orthop Relat Res. 2007 Jul 19;Publish Ahead of Print [Epub ahead of print]

August 2008

18/08/2008

NOISY CERAMIC TOTAL HIPS – WHAT IS THE CAUSE?

Patients with ceramic (and also with metal-on-metal) total hips experience sometimes noises from their new hips. The prevailing theory says that the noises are produced by increased friction between the bearing surfaces of the total (and surface) hip joint. A thin layer of liquid should be present between the surfaces during joint motion causing low-friction and noiseless motion. It is supposed that under certain circumstances such as extreme loading on the hip joint or with faulty position of the component the liquid layer may disappear and the joint then squeaks.

Surgeons at Rothman Institute, Philadelphia, Pennsylvania, USA, found that 2,7% of their 999 patients with ceramic total hips had noisy total hip joints. These patients were carefully x-ray examined even with computer tomography and the position of their ceramic total hips was compared with position of the ceramic total hips that produced no noises. No difference between these two groups was found. The authors conclude somehow surprisingly: “Although malposition could be an important contributing factor (to squeaking) the latter cannot be the sole reason based on our findings. Further investigation to elucidate the etiology is warranted”.

Information for you: It seems really that the surgeons do not know why some ceramic and metal on metal total hips squeak. From the most reports it is, however, apparent that squeaking is not foreboding an approaching failure

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Reference:

Restrepo C. et al. The noisy ceramic hip: is component malpositioning the cause? J Arthroplasty. 2008 Aug;23(5):643-9

11/08/2008

ZIMMER RECALLS THE DUROM METAL-ON-METAL CUP COMPONENT

Only a few years passed since the Sulzers metallic cup (Inter-OpTM) caused catastrophic failures to their patients and financial catastrophe to the Company. Since then the Zimmer Company took over the Centerpulse Company as was the new name of the Sulzer company. Zimmer Company took over also the Company’s MetasulTM metal-on metal total hip program and continued with a proper total and surface replacement program called DuromRT.

On July 28^th, 2008, the Company announced that it is recalling its Durom cup component from the USA market.

The Durom cup is a not fully hemispherical cup made from a specially developed wrought cobalt chrome alloy. It has very smooth joint surface that guarantees very low friction. It was developed in the 1980’s for Sulzer’s Metasul total hip program. On the outer surface the cup has a porous coating of pure titanium for secure cementless fixation to the socket’s skeleton.

Two unsuccessful metallic cup components from one manufacturer, both of them developed in Switzerland and failing in the USA, appeared on the USA market. Behind this tragedy is an interesting development.

Doctor Lawrence Dorr was the surgeon who should for Sulzer investigate the reliabily of Sulzer’s InterOpTM cup component. As he himself says, he observed failures of this component early but spoke late, so that a massive catastrophe was a fact. As he says, he learned the lection.

As principal investigator for Zimmer, he observed frequent early failures of the new Durom cup components. He says “they just popped out (of the socket” at revision operation. During the second year after surgery, 6% of all patients had their Durom cups removed and 4% are waiting for it: 10% failures during two postoperative years is a catastrophic failure rate for any total / surface hip replacement.

Now, Doctor Dorr informed both FDA and the manufacturer with recommendation to recall this total hip component, but there was no action. Zimmer maintained that wrong technique (of Doctor Dorr) causes the failures, the cup is flawless. So Doctor Dorr took an unusual step: He wrote an open letter to all his colleagues.

In it he wrote: “I can assure you that this (catastrophic failure rates) goes beyond technique.”

Information for you: Manufacturer who invests in purchase of a competitor’s company is usually not willing to loose money by withdrawing the purchased products from the market. Further development will thus be interesting, especially as the Durom total and surface hip replacement products continue to be used on the European continent and in India. As yet no claims about their malfunction were published from there.

Will American surgeons turn to Wright's metal on metal products?

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Reference:

02/08/2008

RETURN TO SPORTS AFTER JOINT REPLACEMENT (HIP and KNEES)

Advances in surgical techniques and total hip and knee construction made it possible to operate on younger patients with greater expectations to participate in sports after the surgery.

Previous studies demonstrated that total joint replacement (replacement of hip and knee joints) did not endow the patients with the capacity to participate in new sports. If the patients did not participate in the sports before the total replacement surgery, they will not start with sports even after a very successful total joint replacement.

The recent study by English surgeons confirmed this previous experience (Wylde 2008).

Three years after total hip and total knee surgery, 35 % of all operated on patients were participating in sport, the most common being swimming, golf, and walking. And this in patients whose mean age ranged from 52 years (surface hip replacement) to 70 years (total knee replacement). 61% of patients who participated in sport before surgery returned to it, mainly patients who played golf and swam. The patients who did not return to sports were often engaged in high impact sports such as badminton and tennis.

Information for you:

There are good and equal chances that you may return to sports after successful hip or knee replacement surgery. On condition that you were engaged in sport before surgery. Even the percentage of patients returning to sport after surface hip replacement in this study was not higher than the percentage engaged in sport after total hip replacement. Another myth punctuated?

Painful total joint precludes participation in sport. Of course, and this study confirmed this common sense knowledge.

See also the chapters Sports after total hip and Total knee and sports

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Reference:

Wylde V et al: Return to sport after joint replacement. J Bone Joint Surgery-Br 2008: 90-B: 920-3

July 2008

31/07/2008

ARTIFICIAL MENISCUS RETURNS FUNCTION TO THE KNEE JOINTS.

There are several patients who continue to have knee symptoms after extraction of the damaged meniscus. These patients feel episodes of pain and swelling, catching up episodes, and instability in their operated on knee joints. The function of the knee joints in these patients is severely damaged.

A group of surgeons from several countries demonstrated that these patients can have the function in their knees restored with implantation of an artificial meniscus (Rodkey 2008).

This is a plate of about the form of the removed meniscus, made of collagen. The surgeon sews the artificial meniscus to the rests of the meniscus removed at previous operation. Successively the collagen structure is replaced by a patient’s own menisceal tissue that grows into the scaffold provided by the collagen substrate. 75% of the patients treated with the collagen meniscus recovered full function in their previously deficient knees and retained it in > 5 yers.

Information for you: This is not an operation for everybody. It does not work for patients with damaged knee joint cartilage. And it does not work for patients with “fresh” meniscus damages.

On the other hand, this report with nice pictures of newly formed menisceal tissue forces us to rethink our school knowledge about meniscus as a structure without blood vessels. It demonstrates not only that menisceal tissue can heal, it shows also that it can form a whole (yes, almost a whole) new meniscus with its weight bearing function retained.

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Reference:

William G. Rodkey et al: Comparison of the Collagen Meniscus Implant with Partial Meniscectomy. A Prospective Randomized Trial. J Bone Joint Surg Am. 2008;90-A:1413-1426.

28/07/2008

MANUFACTURERS STRANGLE FUNDING OF ORTHOPAEDIC DEVICES RESEARCH – IN THE USA

Susan M Rapp discuss in an article in OrthoSupersite the investigation carried out by the U.S. Department of Justice on the money paid by manufacturers of artificial joints to the surgeons using these devices. American papers were speaking about “kick back money”.

After interviewing Doctor Richard Iorio from Lahey’s Clinic, Burlington, MA, USA, Susan Rapp says that one noticeable affect the Department of Justice Investigation would produce will be restriction of financial support to ongoing orthopaedic research from manufacturing companies.. If the situation does not improve soon the future of orthopaedic innovation may be in jeopardy.

Doctor Schwarz who is spokesperson for the Orthopaedic Research Society sees the situation in another perspective. Research of basic science questions will be unaffected according to him, because this research is financed by government money. On the other hand, research and development of new orthopaedic devices, such as development of new types of artificial total joints, will be impacted, thinks Doctor Schwarz.

Information for you: The situation on the market of artificial total joints is close to chaos. The manufacturing company can stay in the trade only when churning out steady new models of total joints.

This competition has dire consequences. According to some reports, 80% of all total hip models on the English market do not have any report of their efficacy. Report about the results of total hips and knees >10 years after surgery are rare. And when such record are published, the studied total joint model is no longer available on the market,

From this perspective, it seems to me that some restriction of the steady stream of new models of total joints may have good effect.

On the other hand, only a cursory look in the current orthopaedic journals will demonstrate to you that the development of modern total joints is financed mainly by manufacturers’ money. And when you look in the chapter Global improvement you will discover that these results are continually improving. So these money are making a lot of good.

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Reference:

Rapp S.M.: ORTHOPEDICS TODAY 2008; 28:70

10/07/2008

PSEUDOTUMORS AROUND SURFACE REPLACED HIPS – A NEW COMPLICATION?

Scientists knew for long that body tissues’ reaction to wear products of metal-metal hip joints, compared with reaction to wear products of polyethylene or ceramic total hips, is different. Microscopic examination of tissues around the failed metal-metal total hips showed that body reacts to presence of metallic wear products by strangling the small arteries in the tissues around the metal on metal hip joints. Death of these soft tissues follows. If the patient is allergic to metals contained in the metal-metal total joint the death of the tissues may be extensive.

See also the chapter Metal-metal total hips

As yet, this finding did not arouse much attention among the surgeons who use metal-metal total hip models.

This may, however, change.

Scientists at the Norwich University in England studied 20 patients who came to the radiological department because of “early” unexplained pain after total hip replacement with metal-metal total hips (Toms 2008). After conventional x-ray examination the patients got the conventional information that “there is nothing wrong with their total hips”. Thus, there was nothing that could explain the pain around the total hips of these patients.

Then one proceeded with MRI examination of these 20 total hips; this examination changed the situation dramatically. On MRI pictures of all 20 total hips one found profound soft tissue changes: large collections of free fluid around the total hip, areas of soft tissue edema, and areas of muscle damage. Because these MRI examinations were done 11 -34 months after the surgery the findings cannot be sequels of a recent operation trauma. Some of the patients had a revision operation and this had found large areas of necrotic tissue around the painful metal-metal total hips.

Changes described by the Norwich radiologists were relatively early (<3 years postoperatively) findings. Recently, however, British surgeons, pathologists, radiologists, and biomechanical engineers working at the famous Nuffield Orthopaedic Centre of The Oxford University, England, published an article with the ominous title “Pseudotumours associated with metal-on-metal resurfacing” (Pandit 2008). The authors describe 20 surface hip replacements (in 17 patients) where developed large soft tissue masses, tumor-like, around the surface replaced hip joints. The tumors consisted mostly of necrotic (dead ) soft tissues that were mixed with a special kind of white blood cells (lymphocytes).

Picture: Artist’s picture of a pseudotumor on the back- and inside of a surface replaced hip.

The gray pseudotumor masses are connected with the surface replaced hip joint cavity and bulge out in the groin area

These pseudotumours developed > 5 years after surface replacement and caused considerable discomfort to the patients, in some nerve palsy or dislocation. In some patients the masses were even palpable in the groin. The authors stress the fact that these pseudotumours may be difficult to discover on MRI if they are small; the metal artifacts produced by metallic parts of the surface hips will overshadow them. Ultrasound seems to be the best method to expose these pseudotumors.

All the patients were women and the presentation of the pseudotumors was variable. The most common symptom was discomfort in the region of the hip. 15 of the surface replaced hips with pseudotumors already needed revision operation or were awaiting it.

These 20 pseudotumor cases appeared among the 1300 surface hip replacement operations done by the authors, so that the authors estimate that approximately 1% of patients who have a metal-on-metal resurfacing will develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris.

Information to you:

First: If you have pain around your total /surface hip, don’t accept “the nothing wrong” message from your doctor, especially if you have a metal-on-metal total/surface hip. A good ultrasound examination may discover the pseudotumor and may be done on most radiological departments. Conventional MRI is difficult to use because of the “scattering” effects of metal components. A radiological department with special computer programs to get rid of these "scattering effects" will be needed.

Second, there appears again the question of metal hypersensitivity in patients to be operated on with metal-metal total / surface hips. The authors did not test their patients in this way. One can understand this omission because there is as yet no standard, reliable test method to assess this allergy. (See also the chapter Allergy to metals). The authors are rightly concerned that with time the incidence of these pseudotumours may increase. They say that further investigation is required to define their cause.

In my opinion, when the manufacturers are currently paying million dollar fees to surgeons for using their joint replacement devices, they could stretch their financing to allergy specialists too for a comprehensive study of metal allergy in patients bearing their metal products.

And one calm wonder at last: there are many centers having done thousands of surface hip replacements with observation times 5 years and longer, some of them in England and on the European continent. Why do we not hear from them?

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Reference:
Toms AP, et al: MRI of early symptomatic metal-on-metal total hip arthroplasty: a retrospective review of radiological findings in 20 hips. Clin Radiol. 2008; 63(1):49-58..

H. Pandit, et al: Pseudotumours associated with metal-on-metal hip resurfacings. Journal of Bone and Joint Surgery - British Volume, Vol 90-B, 847-851.

07/07/2008

DO HIGH BLOOD LEVELS OF METAL IONS IN PATIENTS WITH METAL –METAL THs MATTER?

Several studies demonstrated that wear of metal-metal total hips produce high blood levels of two metals – cobalt and chrome. See also the chapter Metal on metal total hip.

Whereas chrome is excreted from the body by lever and bowels route, cobalt is excreted by the kidney. Thus, in patients with chronic kidney disease the excretion of cobalt by urine would suffer. Actually, there are occasional reports demonstrating that patients with chronic renal insufficiency who have had a metal-metal total hip replacement also had > 100 higher blood levels of cobalt than similar patients with normal kidney function.

For this reason, most surgeons would not implant a metal-metal total / surface hip to patients with bad kidney function.

But do these extremely high blood metal levels really do harm to these patients?

Not at all, according to a recently published report from Korea (Hur 2008).

Korean surgeons followed five patients with chronic renal failure that had implanted cementless metal-metal total hips for up to five years after the surgery.

The blood (serum) ion levels of cobalt and chrome of these patients with insufficient kidney function were compared with the blood levels of other patients, also with metal-metal hip replacements, who had healthy kidneys.

It appeared that the blood ion levels of cobalt were 100 times higher in patients with insufficient kidney function only. The blood ion levels of chrome were equally high in both patient groups.

Both patient groups have had equally good results of their total hip replacement operation, the very high blood levels of cobalt obviously did not influence the function of the metal-metal total hip during the five postoperative years.

The authors conclude that “Side effects related to elevation of serum cobalt or serum chromium concentration were not identified and overall clinical results were good 4 years after surgery.” They, however, add cautiously that longer follow up is necessary to determine any clinical effects of the elevated levels of serum cobalt and / or serum chrome.

Information for you:

This report adds to the confusion. It shows that even patients with chronic renal failure can live well with a meta-metal total hip joint and blood levels of cobalt that are several 100 times higher than is normal. I only wonder how long the human body can tolerate such excessive high blood levels of cobalt. Do this and other similar reports show that the limits of occupational exposure to cobalt (and chrome) stipulated by occupational medicine simply do not apply for patients with metal-metal total hips?

There are several reports demonstrating that elevated blood levels of metal ions cause damages of white blood cells (their chromosomes). But also these reports do not see any side effects of this damage.

Is it possible that the scientists do not look in right places when assessing the damages these elevated blood metal levels are causing to the human body?

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Reference:
Hur CI, et al: . Serum Ion Level After Metal-on-metal THA in Patients With Renal Failure. Clin Orthop Relat Res. 2008; 466(3):696-9. Epub 2008 Feb 10

04/07/2008

ANTIBIOTIC – IMPREGNATED BONE CEMENT FOR TOTAL HIP REPLACEMENT

In the late 1960, the German surgeon Professor Buchholtz got the idea to admix the powerful antibiotic gentamycin to the bone cement that was then used generally on the European continent for fixation of total joints.

Laboratory experiments demonstrated that gentamycin eluted from Palacos TM bone cement several months after the surgery in just the right concentration: the concentration was sufficiently high to kill every bacterium that occurred close to the operation wound, yet not so high that it might produce unwanted side effects in the patient’s body.

Although originally devised for revision operations of infected total hips, the antibiotic-impregnated bone cement (gentamycin – Palacos) was soon used on the European continent also for routine primary total hip replacements, as yet another part of antibiotic prophylaxis. (see also the chapter Prophylactic antibiotics).

Interestingly, the use of antibiotic - impregnated bone cement spread to the USA, yet without official approval of the authorities. Its use was approved only recently by the FDA, more than 30 years after its introduction on the European continent. It is thus interesting that a group of American surgeons published recently a comprehensive study of reports on antibiotic-impregnated bone cement to get answer on two questions:

First, did the use of antibiotic-impregnated bone cement reduce the risk of infections in total hip infections?

Second, does the use of antibiotic-impregnated bone cement reduce the risk of other failures (aseptic loosening) of total hip replacement?

A comprehensive study of reports published from 1966 to 2004 discovered 19 studies that contained reports on infections in 36 000 total hip operations.

Answer on the first question was in the affirmative: Use of antibiotic-impregnated bone cement lowered infection rate in primary total hip replacement by 50%, from 2.3% in patients who had simple bone cement to 1.2% in patients who had antibiotic-impregnated bone cement for fixation of their total hips.

Answer on the second question was also in the affirmative: Use of antibiotic-impregnated bone cement diminished significantly the overall risk of failure of total hip replacement, from 4,1% in patients who had non-impregnated bone cement to 3.1% of failures that occurred in patients who had antibiotic-impregnated bone cement used for fixation of their total hips.

The use of antibiotic-impregnated bone cement for revision operation of infected total hips lowered the risk of a new infection by 40%.

No side effects of the gentamycin were reported in these studies.

Information for you: This is an important study that shows how weak are the grounds on which reposes the science of total joint replacement. Thousands and thousands of reports were written during the 40 years about the prophylactic antibiotics and the use of antibiotic impregnated bone cement. Yet, only four surgeons groups wrote together 13 scientifically impeccable reports about the effect in real life. The rest are anecdotic remembrances, considerations, comments that fill the pages of scientific journals.

Probably because the idea of antibiotic-impregnated bone cement originated outside the USA, its approval by official American authorities was deemed to wait for > 30 years.

The study raises also some important questions: If antibiotic-impregnated bone cement saved 1% of patients from revision operation, how many total joints, on the other hand, failed because of “cement disease”? Does “cement disease” really exists?

Does the publication of this study mean that American surgeon will begin to use bone cement for fixation of their total hips in primary total hip replacements?

Only future will tell.

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Reference:
Parvizi J et al: Efficacy of antibiotic impregnated cement in total hip replacement. Acta Orthopaedica 2008; 79: 335- 41

01/07/2008

SHOULD YOU HAVE PROPHYLACTIC ANTIBIOTICS BEFORE THE VISIT AT YOUR DENTIST?

The routine administration of prophylactic antibiotics before routine dental interventions in patients with total joints is a contentious issue. The basic question to answer is:

Does routine dental procedure on non-infected teeth and palate push mouth bacteria into blood circulation, and can these circulating bacteria land on the total joints in patient's body and cause infection there?

To me, the issue is much like the global warming debate. One screams people bearing total joints that infection of their total joints is looming after routine procedures done on their teeth; yet the evidence that total joints are at danger of infection after routine dental procedures is still lacking. In spite of this lack of evidence the surgeons and dentists recommend use of prophylactic antibiotics to prevent this unproven event, Preventive precaution is called such logic in global warming debate.

Preventive precaution with prophylactic antibiotics before routine dental intervention costs money, is ineffective, or even worse may be dangerous for certain patients. See also the chapter Prophylactic antibiotics.

In an Editorial in the Journal of Bone and Joint Surgery, two British microbiologists (Oswald and Gould, 2008) summarize the present knowledge about this issue: there is no evidence to link prosthetic joint infections to dental procedures and none to prove that antibiotic prophylaxis in this case is effective. The continued use of antibiotics for these cases would be expensive, contribute to an increase in bacterial resistance, lead to increased morbidity as a result of adverse side-effects of antibiotics and increase the risk of death because allergy to antibiotics. It is clear that better oral hygiene is the answer rather than the administration of antibiotics.

In the same journal, a group of Swiss and French microbiologists, infection disease specialists, and orthopaedic surgeons present a concise summary of the present knowledge about the efficacy of prophylactic antibiotics used before routine dental procedures to prevent total joint infection (Uçkay 2008).

Their report essentially boils down to the following conclusions:

Prophylactic antibiotics are not required before a dental intervention in patients with artificial joints. However, an existing dental infection requires intensive antibiotic treatment. Patients who are less then one year after total joint surgery should have an antibiotic prophylaxis before some selected dental procedures. This recommendation is based, however, more on litigation fear than on proven facts. Because even every-day activities, as intensive chewing, may push small amounts of bacteria from mouth into the blood stream, all total joint patients should be advised to keep good oral hygiene.

Basically these recommendations follow the Statement of the American Dental Association and the American Academy of Orthopaedic Surgeons from 2003. See the chapter Prophylactic antibiotics to read it.

Information for you: The reasons why not to use preventive antibiotics before routine dental procedures should be considered seriously. Remember that the allergic chock caused by hypersensitivity to antibiotics has up to 20% mortality. In the end, however, the decision whether to use or not to use the antibiotics will depend on the personal relation between the patient and his / her dentist or surgeon.

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Reference:

T. F. Oswald, K. Gould: Dental treatment and prosthetic joints ANTIBIOTICS ARE NOT THE ANSWER! Journal of Bone and Joint Surgery 2008 - British Volume, 90-B, 825-826

I. Uçkay and col.: Antibiotic prophylaxis before invasive dental procedures in patients with arthroplasties of the hip and knee Journal of Bone and Joint Surgery 2008 - British Volume, 90-B, 833 -838

June 2008

24/06/2008

EXCELLENT LONG TERM RESULTS OF TOTAL HIP AND TOTAL KNEES

Some surgeons are still telling their patients that a totally replaced hip / knee joint has only 50% chance to last 20 years. Besides that such tales scare the patients, it is not true. There are reliable statistics demonstrating that more than 80% of all total hip devices operated on in the 1970’s, when the operation technique and the total hip devices were still rather primitive, survived and worked 20 years. It is a big paradox that the majority of these proven devices are no longer on the market, whereas the majority of the contemporary total joints on the market have no long term record. See also the chapter Conventional total hip-Details. Thus, reports about the long term results of total hip and total knee models that are still used are worth to notice.

Norwegian surgeons reported recently the long term results of the Zweymüller cementless total hip (Reigstad 2008). Picture: Zweymüller cementless total hip. Click on the icon for a full size picture.

They followed patients with this hip model for a mean of 18 years and found that totally 12% of them failed during this period. A very good performance because the majority of patients were “young”, the mean age of the patients was only 52 years (range 24 to 68 years).

The majority of the failures (11%) were caused by failure of the cup component, whereas only 5% of all stems failed during this follow-up period. This difference, the high failure rate of the cup components and the very low failure rate of stem components is characteristic for modern cementless total hips. So it was also in this “old” cementless model.

The manufacturer replaced successively the failing material (polyethylene) in the cup component of the Zweymüller total hip by introducing ceramic bearing surfaces for both components (cup & stem) and cross-linked polyethylene material. The short term results of these modifications are promising but the long term results of these improved models are, however, not known yet.

This report concerns results achieved in one Norwegian hospital with 75 total hip operations with the so called SL Zweymüller stem. It is worth to note that the survival rate of Zweymüller’s total hip calculated from the pooled results in all 11 Norwegian hospitals that use this model was less favorable: only 78% of them survived ten years. Comparison of the present report with these all-Norwegian results is, however, not easy. The all-Norwegian statistics contains namely two models: older Alloclassic and newer SL modifications.

The American surgeon Melvin Ritter and his colleagues published recently 20 years results of the AGC total knee model (Ritter 2008). The authors found that 97.8% total knees of this model survived 20 years. The results were assembled on patients operated on between 1983 through to 2004, so only 36 patients were followed for the full 20 year interval.

But still, 97.8% success rate is impressive. Such figure looks more like the result of a communistic election than results of any known surgical procedure. The manufacturer of the AGC total knee (Biomet) probably subsidized the study and its authors, although these data are lacking in the published report.

With success rates close to 199%, factors that in other studies influence the results of total knee replacement (age, gender, diagnosis, alignment) have very limited influence on the results in this series.

Information for you.

The Zweymüller’s name actually is attached only to the stem component of this total hip device. And the stem component is obviously successful, also in other reports. But the statistics, with the many small modifications of individual models is a mess, also in other models. So comparison is difficult and the authors of this report did not mention the worse all-Norwegian results with this device.

A general observation from this messy statistics is, however, emerging: The cementless stem components are generally successful, the weak point are the cups, mainly their polyethylene in-liners.

The AGC total knee model has a non modular tibial component; the polyethylene plate in the tibial component is fixed in place on the metallic back-up by the manufacturer in the factory, not by the surgeon in the operation room as in many other total knee models. According to Doctor Ritter this construction is the factor that is protecting the polyethylene plate from destruction by wear.

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Reference:

Reigstad O. et al: Excellent long-term survival of an uncemented press-fit stem…Acta Orthopaedica 2008; 79: 194 – 202

Ritter M et al: 20 year Follow-up of the AGC total knee replacement. Proceeding of the International Symposium of Current Topics in Knee arthroplasty, The Journal of Bone Joint Surg Br, 2008, Symposium, 1.

18/06/2008

NASAL OINTMENT MAY REDUCE THE RISK OF POSTOPERATIVE INFECTIONS IN TOTAL JOINT REPLACEMENTS

It has been since long known that between 30 to 100% of all postoperative infections with Staphylococcus aureus are caused by patient’s own bacterial strain. (See also the chapter Bacteria characteristics). Very often identical Staphylococcus strain colonizes patient’s wound and patient’s nose and may be easily cultured from both places. Not to wonder because nose (nasal flares) comes in contact with all air that the patient consumes; if this air contains colonies of Staphylococcus aureus, it is only natural that they are filtered off and stay here.

Since long, bacteriologists and infection doctors were investigating the possibility that eradication of Staphylococcus bacteria in patient’s nose (and skin) will diminish the risk of postoperative infection. These studies gave contradictory results.

American infection specialist doctors tested again the hypothesis that eradication of Staphylococcus aureus strains from the nose and skin of the patients will diminish the risk of postoperative infections after total joint replacements with this bacterial strain (Rao 2008). All such studies are technically difficult, because you will to have two patient groups: the one who will get the preoperative prophylactic treatment against the Staphylococcus strains and the other one with no such treatment. To this second group you would have actually to say that they will have no protection.

To solve this problem, the authors chose two groups of surgeons instead: the surgeons in the first group consented that their patients would have bacterial screening before the operation to detect contamination of their noses with Staphylococcus aureus strains. Patients with positive growth will receive prophylactic treatment five days long, consisting of application of antibiotic ointment (mupirocin) in the nares twice a day and whole body baths in chlorhexidine solutions daily.

The 1330 patients operated on by the second group of surgeons would not have any screening or prophylactic treatment.

The studied patient group consisted of 629 patients out of whom 26% had positive growth of Staphylococcus strains and received prophylactic treatment.

Follow up one year after total joint surgery demonstrated that the 164 patients who were preoperatively treated with nasal ointment and chlorhexidine baths did not develop any postoperative staphylococcus infection, whereas the patients in the second, not preventively treated group, had 0.9% postoperative infections with Staph. aureus.

The preventive treatment did not produce any side effects.

Information for you:

Probably there are about 25% of carriers of the dangerous Staphylococcus aureus strain among us, not knowing about their “carrier state”. They may be a danger to themselves when operated on with total joint arthroplasty which is extremely sensitive for infection. These facts were well known in the past.

The new knowledge from this study shows that there may be a place for preventive treatment of these selected patients. The local treatment of nares removed Staphylococcus bacteria in 83% of the carriers and at the same time eliminated the risk of postoperative infection with Staphylococcus aureus strains in them.

It must be pointed out, however, that there is no place for general treatment of all patients awaiting total joint replacement with nasal antibiotic ointments; studies have shown that such proceeding does not diminish the risk of postoperative infection but may increase the antibiotic resistance of involved bacteria.

If you are anxious about a postoperative infection after your total joint operation you may always ask your surgeon to send you for taking bacterial swabs from your nares. If positive for Staphylococcus aureus you may then have this preoperative preventive treatment.

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Reference:

Rao N et al.: A preoperative decolonization… Clin Orthop Relat Res 2008; 466: 1343 - 8

14/06/2008

NEW METHOD FOR CONTROL OF POSTOPERATIVE PAIN – No morphine

Modern trend aims at sending the patients who had their hip and knee joints replaced home almost immediately after surgery, just the last dressing has been put on. There are good reasons for this hurry. One reason is that the risk of hospital superinfection with hospital bacteria increases with every hour the patient stays in the hospital; another is the risk of DVT (Deep Vein Thrombosis) that increases for patients immobilized on the hospital beds.

One of the reasons why the patients stay longer in the hospitals is the postoperative pain. The opiate drugs (morphine and its derivates) that effectively relieve the severe postoperative pain make the patients also drowsy, nauseous and unable to leave the hospital bed. On the other hand, the non-opiate drugs such as paracetamol, are unable to relieve the severe postoperative pain that appears during the first 24 - 48 postoperative hours.

In this situation, several surgeons developed the idea to infiltrate the damaged tissues in the operation area with local anaesthetic solution. This procedure would stop generation of pain impulses in the damaged nerves of the operation wound and block up the transfer of these pain impulses to the patient’s brain.

Two Australian surgeons developed a well well-reasoned procedure how to infiltrate the soft tissues of the operation wound with a mixture of local anaesthetic and NSAIDs (Kerr 2008). The NSAIDs were added to the solution because they should mitigate the inflammation reaction that always follows the surgical trauma.

The surgeon injected the solution in the tissues around the operated on joint just before the end of the operation. The surgeon also laid a thin catheter (tube) from outside to the joint space. Through this catheter the surgeon injected later on (4 – 9 hours after surgery) additional aneasthetic solution to suppress increasing postoperative pain when the anaesthetic effect of the first injection wore out.

Picture: Pain catheter inlaid in total knee joint at the end of surgery. The transparent catheter is outlined by two gray lines (arrows).

The last anaesthetic injection through this catheter was injected about 20 hours postoperatively, when the catheter was also withdrawn.

The results of this anaesthetic method, which the authors used on patients operated on with surface replacement and total hips and total knees seem promising.

Morphin injection during the first 24 postoperative hours was necessary only in 19% of total hip patients. The analgesic effect of this method was smaller in surface replacement surgery (34% of patients needed morphine) and even smaller in total knee replacement (43% patients needed morphine).

This fact also shows that surface hip replacement surgery causes paradoxically more soft tissue trauma. That total knee replacement is more painful than total hip was shown in several previous reports. Perhaps there is additional pain caused by use of tourniquet in total knee surgery.

The measurement of pain is always subjective. The patients in this study assessed their postoperative pain on a 0 to 10 scale: grade 0 signifies no pain and grade 10 represents the worst possible pain.

4 hours after surgery ( the postoperative period when the pain is usually worst) 35% and 36% of total hip and total knee patients, respectively, have had no pain and only 13% and 16 % of them had worse than grade 3 pain.

Information for you:

Control of postoperative pain by local infiltration was tried by several other surgeons but “met with only limited success”. The injection of large volume of anesthetic solution with a long needle through the skin around the operation wound is painful in itself. Many surgeons used also corticosteroids locally to mitigate the inflammatory response, which might cause additional pain.

The Australian surgeons used inlaid catheter which made later infiltrations of joint tissues not painful. They also used NSAIDs to mitigate the inflammatory response in tissues around the replaced joint which does not produce painful local reaction. NSAIDs, however, may also cause problems; this method could not be used in patients allergic to NSAIDs, or in patients in whom the NSAIDs are forbidden for renal disease.

One patient in this series also developed "late" bleeding gastric ulcer, however, this patient used NSAID (ibuprofen) longer time. Although the authors state that this patient did it "against instruction", the use of NSAID is a certain risk movement associated with this method.

On the other side, in patients where this anaesthetic method meets no problem it really accelerates the mobilization of the patient. The majority of Australian patients in this series were mobilized 11 to 13 hours after surgery (surface hip patients already after 9 hours) and were independently walking 20 hours after surgery.

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Reference:

Kerr DR an Kohan L: Local infiltration analgesia: a technique for control of acute postoperative pain…Acta Orthopaedica 2008; 79: 174-183

08/06/2008

LENGTH OF POSTOPERATIVE STAY DEPENDS ON THE WEEKDAY OF OPERATION

(FACTORS INFLUENCING HOSPITAL STAY AFTER TH AND TK OPERATIONS)

The trend today is to shorten the length of hospital stay after total hip and total knee replacement operation from the previous mean 14 days to less than 5 days.

Obviously, there are certain factors that influence the length of hospital stay after these operations. Danish surgeons studied the importance of some factors for the length of hospital stay after total hip and total knee operations (Husted 2008).

In their study there are some surprises but the study mostly confirms what we suspected earlier. Perhaps there lies the study’s value.

The Danish surgeons studied 712 patients, operated on with TH or TK replacement, who were managed with the new “fact-track” method. (Fast-track perioperative course is a new perioperative and postoperative patient management method aiming at diminishing the postoperative complications inclusive of pain, and quick patient mobilization). The success of this management reveals itself as shorter length of hospital stay.

The mean length of patient hospital stay in the Danish study was 4 days, equal for patients operated on with total hip and total knee replacement. 42% of all patients could leave the hospital by the third day.

Comprehensive preoperative information did not shorten the length of stay, no surprise discovery because also other studies demonstrated that comprehensive preoperative information influences only marginally the length of postoperative stay after TH and TK.

Among factors that lengthened postoperative hospital stay were: Living alone, advanced age, and be affected by other diseases. This may be expected and appeared also in other studies.

More surprising was the fact that women had longer postoperative hospital stay tan men; this fact that appeared in other studies too, has no reasonable explanation.

Another surprise was the fact that length of postoperative hospital stay depends on the weekday of operation. Shortest hospital stay had patients operated on Tuesdays; longest hospital stay had patients operated on Thursdays. This difference can be explained by the personal routines at the Danish hospitals, with severely reduced personnel (especially physiotherapists) at weekends.

Need of blood transfusion signals a more complicated surgery, weaker patient, or both. No surprise thus that transfunding blood lengthens hospital stay.

Information for you:

Young and healthy male patients who have a support person at home, who were operated on Tuesdays have the greatest chance to leave the hospital in 3 days or less in a Danish hospital (and probably elsewhere too).

Even if participating in preoperative patient information sessions does not significantly shortens length of postoperative stay according to this study, do participate in them. There are benefits to it

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Reference:

Husted H. et al.: Predictors of length of stay and patient satisfaction after hip and knee replacement surgery. Acta Orthopaedica 2008; 79, 168-173.

05/05/2008

CERAMIC HIPS DO SQUEAK

Squeaking of ceramic hips received much interest lately. Yet, the facts are meager. Whereas there are theories purporting that squeaking is caused by wrong position of ceramic components the surgeons still do not know whether the squeaking is completely innocent or whether it heralds some potential complication, such as increased rim wear.

A group of Danish surgeons interviewed their 107 patients with ceramic total hips telephonically and asked whether they hear any sounds from their ceramic hips (Varnum 2008).

It appeared that totally 17% of them heard some noises from their ceramic total hips. Some of the patients noticed the sounds only periodically during the postoperative course, but in 10% the noise (squeaking, grating, clicking) has been permanent.

The authors related the position of ceramic hip components, as seen on conventional x-rays, to the occurrence of sounds, but found no relation.

From this superficial study it seems that the sounds from ceramic total hips are not related to wrong position of total hip components.

In an interview in the commercial journal Ortopedics Today in April 2008, the Boston surgeon Doctor Stephen Murphy said that the sounds from ceramic total hip are related to certain total hip models, but he presented no statistics either. May it be that the sounds from ceramic hips are design related? As yet, we do not know.

Actually, the manufacturer of one model of ceramic total hips, Stryker, recalled in January 2008 one of his ceramic cups, the Trident cup TM, after warnings from FDA. (The recall applied only to products made in Ireland). The fault that caused the recall was bacterial contamination of the product but in its letter the FDA also mentioned that patients claimed about squeaking noises from their Trident total hips.

Information for you: It seems that squeaking from ceramic hips is causing more interest and perhaps also anxiety today than in the past. There is, however, still no reliable information about whether the sounds are a sign of bad outcome.

References:

Varnum C, et al.. Ceramic bearings in total hip arthroplasty: frequency and type of noises. Paper presented at the 9th European Congress of Orthopaedics and Traumatology Congress in Nice, France. May 29-June 1, 2008.

04/06/2008

A NEW MIS METHOD FOR TOTAL HIP REPLACEMENT

Development of access routes – approaches to the hip joint has a long history. The well known hero on this area is the Boston surgeon of Norwegian descent Marius Smith-Peterson who developed in the 1920’s an anterior approach to the hip joint that spares maximally the soft tissues around the joint.

In the past, when a surgeon developed a new operation technique, he/she usually spread the knowledge through direct contact with colleagues, residents under his training, eventually publication in a journal. All relatively slow methods.

Present day surgeons usually collaborate closely with the manufacturer of orthopaedic instruments and devices. The manufacturer than takes care of the spread of the information about the new operation method.

Total hip replacement is a “big surgery” entailing big surgical trauma for the patient. No wonder that the surgeons are developing modifications of current operation technique to minimize this trauma.

The minimal incision surgery (MIS), although developed to minimize this trauma may be still very traumatic procedure. One of the very traumatic moments is the dislocation of the femoral head into the operation wound that may cause severe damage to the soft tissues. (See also Mini Incision TH surgery).

Doctor Murphy of Boston, USA, developed a Supercap technique that does not require dislocation of the femoral head during total hip replacement procedure.

The surgeon uses special (patented) instruments with which the head is sawed off and extracted through a small operation wound. This should be a more careful and tender approach compared with the dislocation of the femoral head through the small mini-incision wound.

This picture shows the special technique that is used to saw off the femoral head through the small wound. The sawed off head is still inside the hip joint and will be removed in the next step.

(clip on the icon for a full size picture)

As it should be in these days of “patented all” operations and instruments, the Wright manufacturer has patented the SuperCap R procedure and provides a comprehensive information material and interactive learning facilities. Obviously, a quick track to spread this new soft tissue sparing MIS technique of total hip replacement.

Information for you: As described this is a sound operation technique in theory. If it really diminishes the surgical trauma so much should the future show. As yet, however, there are no published results of this SuperCap R technique available. But then, about 80% of all total hip models that are used today have no published documentation of their efficacy.

References: http://www.wmt.com/physicians/products/hips/SuperCapSurgicalTech.pdf

April 2008

22/04/2008

SURFACE HIP REPLACEMENT – CURRENT RECOMMENDATIONS

This is a current concept review article, directed to surgeons, but it contains a lot of information that may be useful also for patients and lay people (Shimmin 2008).

For me two areas seem to be important.

First, the authors show that all big manufacturers produce their own model of surface hip replacement device. Typically, the acetabular component is inserted cementless while the femoral component is inserted with bone cement. However, the clinical results are known only for a minority of these models; even for these models the results are only mid term with follow up > 5 years but still shorter than 10 years.

The typical successful patient is a young male patient > 82 kg weight!, with good skeleton quality and normal kidney function! The term “ Young” means <65 years for men and for women <55 years of age.

Surface replacement is not recommended for older patients, patients with poor bone quality, women in child-bearing age, patients with known hypersensitivity to metal, and patients with leg length discrepancy > 2cm.

Patients who absolutely should not have surface hip replacement are patients with marked osteoporosis in their skeletons and patients with known long term kidney disease.

Second, the authors point to the as yet less known problem of metal hypersensitivity that may produce failure of the surface replacement device. Such failure may be demonstrated by a special cell reaction in the tissues around the surface hip device. It has the long name “aseptic lymphocytic vasculitis associated lesion or ALVAL”. Without histological examination this failure will simulate the usual loosening failure.

Yet, at present little is known how best to monitor the changes of blood metal levels in surface replacement patients, or whether one should monitor them at all. Neither is known, whether there are any tests to discover patients with hidden metal hypersensitivity that will develop the allergic reaction after implantation of surface hip replacement.

The authors are cautious to say that “Some orthopaedic surgeon innovators …as well as industry marketers have suggested that it is realistic for patients to return to high impact sports. However, …caution should be used when advising patients about sustained high activity…”.

Information for you: It seems that these recommendations, produced by well known and well experienced surgeons (one from Australia, one from the USA), should be spread among the people awaiting hip replacement surgery to mitigate sometimes inappropriately high expectations from this reinvented operation procedure.

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References:

Shimmin A. et al: Metal – on metal hip resurfacing arthroplasty. J Bone Joint Surgery – Am 2008; 90-A: 637 - 54

21/04/2008

METAL ON METAL HIP REPLACEMENT CAUSES CHROMOSOME CHANGES

With the increasing number of surface hip replacements done on young patients concerns about side effects of metal on metal hip replacement devices are increasing. The situation is unclear: does the modern metal-on-metal hip replacement device, that produce increased metal blood level, cause any damage to the patients in the long term?

The answer on this question is, of course, not possible: the modern surface hip replacement devices are for the most part in use less than 10 years.

The scientists thus turn to the “historical” devices and come to some interesting conclusions.

A group of British surgeons and scientists working at the Bristorl Implants Research Center published an interesting report on patients who had a metal-on-metal total hip for 35 years on average (Dunstan 2008). As a control they used two groups: one group were people not operated on and non smokers, the other one were patients in whom the metal-on-metal total hip was removed and replaced with a metal-on-polyethylene group.

They studied the changes of chromosomes in the patient’s blood cells called lymphocytes by painting the chromosomes with twenty-five color stains. This method produces very nice pictures, something of “modern art pictures” as you see on this picture.

Picture: Chromosome aberrations in lymphocytes of a patient having the metal on metal total hip for 35 years. The chromosomes appear always in pairs. The changed pairs are encircled. In some pairs (9,16,17) one partner is lacking, in other pairs (2,15) the one chromosome is changed. From Dunstan et al article. (ChromosAberr_MetalTH_JBApr08)

The scientists discovered that the patients with metal-on metal total hips had several changes in their chromosomes ( the scientific term is “aberration”) than people in the two other groups. Especially important is the observation that patients who had their metal on metal total hip removed and replaced with the conventional one had “normal” chromosomes. Obviously, removal of metal of metal total hip and replacement with the conventional (polyethylene-on-metal) total hip made the chromosomal aberration to disappear.

Information to you:

This is an excellent article with perfect documentation, but it should not scare you: All studied patients with long time implantation of total hip were operated on for tumor. The implants were of old models, the alloys from which the models were made are not used today.

But these chromosomal changes are used in the argumentation and concerns about the present day use of metal-on-metal surface replacements, so you should know about it.

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References:

Dunstan E. et al: Chromosomal Aberrations in the Peripheral Blood of Patients With Metal-on-Metal Hip Bearings. J Bone Joint Surg- Am 2008; 90-A: 517 - 22

20/04/2008

BIRMINGHAM SURFACE HIP REPLACEMENT – ONE OF THE MOST OFTEN USED AND SUCCESSFUL

Birmingham surface hip is an English product with good spread, perhaps mainly to countries with ties to England. So it was the most commonly used hip replacement device in Australia in the last years. As yet, totally over 60 000 Birmingham surface replacements were carried out since the device was put on the market in 1997.

Yet, only few studies from independent centers were published about the results from independent centers, most reports were published from the McMinn's Birmingham centre.

Recently, however, surgeons from the renowned Nuffield Orthopaedic Centre in Oxford in England published a very comprehensive report on the results of 610 Birmingham surface hip replacements done in 532 patients who were followed up for between two to eight years (Steffen 2008). These were mainly young patients; their mean age was 52 years.

95% of the Birmingham surface devices survived seven years which is clearly very good result.

The main complication, leading to failure of the Birmingham surface hip in this study was fracture of the femoral neck (see also the chapter Surface hip replacement). In some patients was, however, seen excessive deposition of metallic wear debris into the soft tissues around the Birmingham hip.

Information for you:

From this study, as from other studies published previously, it appears that surface hip replacement is very good treatment method for young active patients with worn out hip joints. The operation, however, gives best results in strong male patients with strong skeletons. Patients with small hip joints and patients with less strong skeleton (small frail women) are at greater risk for failure by fracture of the femoral neck.

The question of the metallic wear in this metal on metal device needs, according to the authors, “further study”; that phrase usually means that the problem is not too big to stop the use of this clearly successful device.

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References:

Steffen ET et al.: The five-year results of the Birmingham Hip Resurfacing Arthroplasty. J Bone Joint Surg-Br 2008; 90-B: 436 – 43

10/04/2008

POTENT DRUGS AGAINST DVT ASSOCIATED WITH HIGHER RISK OF DEATH AFTER TOTAL HIP REPLACEMENT

The pulmonary embolus, causing sudden death of the patient, is the most dreaded complication of total hip and knee replacement. Several drugs have been used to diminish the risk of this complication, but none of them can prevent the pulmonary embolus totally. See also the chapter Deep vein thrombosis.

Very many studies that evaluated the effect of the preventive drugs showed different results. Very efficient drugs, such as modern derivates of heparin, showed good effect on production of blood clots but also high risk of bleeding, because these drugs actually prevent clotting of the blood; consequently these drugs are called anticoagulants.

One of the most outspoken criticism of the drug prophylaxis against DVT was published already in 1996. Three Brittish surgeons analyzed the reports about the effect of drug prophylaxis against DVT comprising totally 130 000 patients (Murray 1996). Their conclusions from this meta-analysis are worth to cite literally.” The fatal pulmonary embolism rate was 0.1% to 0.2% even in patients who received no prophylaxis. This is an order of magnitude lower than that which is generally quoted, and therefore the potential benefit of prophylaxis is small and may not justify the risks. To balance the risks and benefits we must consider the overall death rate. This was 0.3% to 0.4%, and neither heparin nor any other prophylactic agent caused a significant decrease. Our study demonstrates that there is not enough evidence in the literature to conclude that any form of pharmacological thromboprophylaxis decreases the death rate after total hip replacement. For this reason guidelines which recommend their routine use to prevent death after hip replacement are not justified.“

The USA orthopaedic surgeons prescribing the potent (and bleeding producing) anticoagulant drugs to their total hip and knee patients are lead by the recommendation of American College of Chest Physicians that concluded that use of anticoagulants is “safe and effective protection against thrombotic events”. In the high litigation society, nobody in the USA dares not to follow such powerful recommendation; although many orthopaedic surgeons were maintaining that this recommendation is not applicable to healthy total hip and total knee patients (Dorr 2007).

Moreover, in recent years the anticoagulants became of interest to drug companies who hoped to develop a safe anticoagulant that would prevent clotting of blood and yet would not increase the risk of bleeding. And of course, be economical success too.

As usual, this interest involved publication of comprehensive statistical studies, where the holy Statistical Significance took care of the side effects of the new drug. In some of these studies the new drug caused more than twice as many serious bleeding complications (and deaths) than the very effective old drug Warfarin, but this difference was not “statistically significant”.

The conclusion of these studies was that the studied drug “demonstrates superior efficacy ..with no significant difference with respect to bleeding events, although the rate of major bleeding events was greater with (the drug) than with warfarin” (Colwell 2005). The authors of these studies also acknowledged that they received “ grants or ..payments or other benefits from a commercial entity..”.

Previous studies were all pointed on to demonstrate the efficacy of the new potent drugs to prevent the DVT and PE. Although some of them also followed the death rate of the patients treated with these new drugs as we note previously, none of these studies posed the rather heretic question: may the new potent anticoagulants be associated with higher death rates?

But this question asked by many discontent surgeons was hanging in the air and eventually a group of New York anesthesiologists answered it with a convincing “yes”

A recently published study, conducted by New York anesthesiologists at the Hospital for Special Surgery, showed that potent new anticoagulant drugs not only increased the risk of bleeding, but also that the patients receiving them were at higher risk of death (Sharrock 2008). Doctor Sharrock and colleagues study was an original meta-analysis of 20 previous reports that studied the effects and the risks with the use of modern potent anticoagulants. Not all patient deaths in these 20 studies were caused be bleeding complications, although many were. Moreover, clinical pulmonary embolus occurs despite the use of modern anticoagulants.

So doctor Sharrock and colleagues are asking why the doctors should continue with the stereotyped use of anticoagulants after total hip and knee replacement in healthy patients when their benefits do not outweigh their risks. They say literally: “We believe that ACCP should reconsider their guidelines to reflect the fact that PE occurs despite the use of potent anticoagulants and may, in fact, expose patients to increased mortality after surgery." (ACCP = American College of Chest Physicians)

Two factors caused that this report aroused interest.

First, the authors directly pointed to the fact that preventive use of modern potent anticogulants is associated with substantially increased risk of death for the patients treated with them. At the same time these drugs cannot prevent the risk of PE.

Second, Reuters Health service cited this report, so that not only doctors but also interested lay persons and patients get this important information.

Is it possible that a Vioxx like history is starting here?

Information for you:

Just compare the conclusion made by British surgeons made 12 years ago with the conclusion made by American anesthesiologists recently. It will tell you how much the litigious American society presses the doctors to make decisions not warranted by scientific truth.

If you are a candidate for total hip or total knee surgery discuss carefully with your anesthesiologist the use of anticoagulants after your surgery. The risks of PE in otherwise healthy patients, without risk for DVT and PE are really minimal.

Remember, that there are many hospitals on the European continent using only physical prophylaxis against DVT on patients without risk factors who are operated on with total hip and total knee replacement. And there are surgeons in the USA who use only aspirin as chemical prophylaxis on patients without risk factors for DVT (Dorr 2007)

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References:

Colwell C. et al: Oral direct thrombin inhibitor ximelagatran compared with warfarin… 2005; 87-A: 2169- 77

Dorr L et al.: Multimodal thromboprophylaxis for total hip and knee arthroplasty J Bone Joint Surg-Am 2007; 89-A: 2648 - 57

Murray DW et al.; Thrombosprophylaxis and death after total hip replacement. J Bone Joint Surg-Br 1996; 78-B: 863 - 70

Sharrock NE, et al.: Potent anticoagulants are associated with a higher all-cause mortality rate after hip and knee arthroplasty. Clin Orthop Relat Res. 2008 Mar;466:714-21.

08/04/2008

UNISPACER – REINTRODUCTION OF FAULTY KNEE REPLACEMENT DEVICE.

In the 1950’s, before the surgeons developed well functioning total knee replacement devices, two surgeons had the idea to place a piece of highly polished metal between the worn out knee joint surfaces to mitigate patient’s knee pain. Actually, it was not a new idea; since the early 1800’s there were many attempts to treat the worn out joints by this sorts of arthroplasty: just put any alien material between the two worn out joint surface

The early published results of these MacIntosh and McKeever knee arthroplasties were astonishingly good. The surgeons who published these reports, however, followed only small numbers of operated on patients.

Despite these good, but rare results, the MacIntosh and McKeever devices disappeared from the market. Obviously, the general surgeons found these arthroplasties unreliable. I cannot find these MacIntosh and McKeever arthroplasties even mentioned in standard textbooks of orthopaedic surgery of that time. Yet there were very few surgeons using these devices on very small numbers of patients also later on.

Perhaps was it this fact that gave the manufacturer Zimmer the idea to develop Unispacer. It is a highly polished round piece of metal (cobalt chrome alloy) that is placed inside the knee joint of patients with worn out joint cartilage on the inside of the knee.

Picture: Unispacer (from Zimmer’s information brochure).

(Click on the icon for a full size picture)

No bone cuts are necessary, minimal operation wound suffices to clean the knee joint from the rests of the joint cartilage and place the Unispacer in place between the joint surfaces.

The patient may put weight on the operated on knee joint immediately, and may start the motion training as soon as the postoperative pain allows it.

It may seem that it is an ideal device and ideal operation for young patients, who are too young for total knee replacement or unicompartmental replacement, and are not candidates for tibia osteotomy.

However, it is obviously not

A group of Australian surgeons published recently a report about the early results with this Unispacer (Bailie 2008). They operated on a small group of patients (18 knees) with this device to make an early evaluation. After carefully following up their patients for 2 years they came to the conclusion that “The early results of the Unispacer knee system in this serieshave been disappointing… On the basis of thefindings in this study, the use of the Unispacer knee systemis not recommended.”

Within two years 36% of Unispacers failed. The patients still having the Unispacer in place have had pain in their knees, some of them more severe than the pain before the insertion if this metallic piece.

Information for you:

This is an excellent study of a device based on a treatment concept that is antiquated today. One wonders about the ethical issue of reintroduction of such antiquated devices today. This study is, however, highly commended: it shows how such devices should be evaluated with minimal damage for the patients. Operations done on minimal number of patients and evaluated cerefully, before the device is released for general use.

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References:

A. G. Bailie, et coll. : The Unispacer knee implant. EARLY CLINICAL RESULTS. Journal of Bone and Joint Surgery - British Volume, 2008, Vol 90-B, 446-450.

04/04/2008

OBESE PATIENTS OPERATED ON WITH THR HAVE EQUALLY MUCH RELIEF OF PAIN AS THEIR LEAN COLLEAGUES

There are still surgeons and health organizations denying obese patients total hip replacement. The argument is that obese patients have worse results of this operation and more complications than their lean colleagues.

A group of surgeons working in seven UK hospitals decided to carry out a well designed prospective study to eventually decide whether this is a valid objection or a myth. (Andrew 2008).

The authors followed up totally 1421 total hip replacement operations. Interestingly, all statistics is calculated for total hips, not for patients. Yet, “the patients were categorised into three groups: non-obese (body mass index (BMI) < 30 kg/m²), obese (BMI 30 to 40 kg/m²) and morbidly obese (BMI > 40 kg/m²)”.

After following the patients for 5 years the authors found that there was no difference in patient satisfaction, function of the total hips, complication rates or radiological changes at five years between the groups. The morbidly obese group was significantly younger and required a significantly longer operating time. Obese and morbidly obese patients have as much to gain from total hip replacement as non-obese patients.

Information for you:

There were many similar studies published previously, that came to contradictory results; so this prospective study done among others by scientist at the renowned Oxford University should resolve this issue. But I doubt it. Although the study comprised over 1400 total hip operation, there is obviously a risk for committing what statisticians call a beta error. There were only 18 total hip operations in the morbidly obese group. Not to wonder because there are no many surgeons willing to operate on morbidly obese patients.

My objections are two:

first, the classification of the obese and morbidly obese. This is not the authors problem but the general problem of these studies. In some studies the "hyperobese, morbidly obese" start at BMI 30, in this study at 40. Changing the criteria for morbidly obese would probably change also the results for complication rates profoundly in this study.

The morbidly obese in this study suffered 5.2%, the obese 2.7%, and the non obese patients 1.3% hip dislocations, respectively. The authors say that the difference was not statistically significant, which is difficult to believe. With only 18 total hips in the morbidly obese group, the beta error is probably playing its spell. If you are morbidly obese and find a surgeon who will carry out a total hip replacement on you, be wary of the higher risk of dislocation (and deep infection) of your new total hip.

second, the possibility of the statistical beta error in this study:

18 total hips in morbidly obese patients group may be too few for a reliable statistic analysis. The authors do not publish the usual calculation of the lowest number of operations in this group to avoid the beta error.

I would, however, point out once again the authors conclusion that “Obese and morbidly obese patients have as much to gain from total hip replacement as non-obese patients”

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References:

J. G. Andrew, MD, FRCS(Orth), et al: Obesity in total hip replacement. Journal of Bone and Joint Surgery - British Volume, Vol 90-B, Issue 4, 424-429.

02/04/2008

METHODS TO DISCOVER EARLY CHANGES IN THE JOINT CARTILAGE ARE NEEDED

The majority of total joint replacement operations is done for osteoarthritis, the worn out joint cartilage disease. The scientists are still not sure what causes this disease; see also the chapter Hip joint disease, osteoarthritis.

There is, however, an optimistic belief that if we could discover this disease very early, we could also find an efficient early treatment so that this disease would not progress to the final stage that as yet is treated with total joint replacement.

In a survey by British surgeons the authors discuss the current methods available for diagnosis of osteoarthritis. The majority of diagnostic methods, such as conventional x-ray picture discover osteoarthritis too late, when it has destructed large areas of the joint cartilage (Pollard 2008).

There is hope that the MRI (see Diagnosis hip disease / MRI) combined with the use of the contrast material gadolinium may discover the osteoarthritis in the very early stage.

The new investigation method is based on the fact that the contrast agent with the long name with the long name gadolinium diethylene tri-amine penta-acetic acid (Gd(DTPA)) concentrates in areas of damaged cartilage and these areas can be visualized by MRI procedure. For details see chapter Diagnosis of hip disease / MRI.

The new investigation method is called dGEMRIC for “delayed Gadolinium Enhanced MRI of Cartilage. It involves the intravenous administration of the ionic contrast agent (Gd(DTPA)). After intravenous injection the contrast agents successively diffuses into articular cartilage through the (subchondral) bone. The contrast agent concentrates in areas of cartilage where the degeneration already started on the microscopic level.

This is possible because the contrast agen Gd(DTPA) is fixed in the areas of cartilage devoid of glykosaminoglycans (GAG). GAG are important components of joint cartilage. Their depletion from cartilage is the first step in the cartilage degeneration.

            a                           b

MRI images of the knee joint with incipient osteoarthritis

On the first picture (a) you see the MRI image of the knee joint made with the dGEMRIC method. The yellow color shows the areas depleted from GAG, the red color shows the areas of normal cartilage. It is obvious that the areas of joint cartilage with low concentration of GAG vary along the joint surfaces of the knee joint. One such area is the cartilage on the tibia (arrow) where the osteoarthritis already started on the microscopic level,

On the second picture (b) you see also a MRI image of the same knee, but another (non-ionic) contrast material (also gadolinium) was injected directly into the knee. The joint cartilage (red) image shows a well retained joint cartilage.

Comparing these two pictures demonstrates how useful is the dGEMRIC method in discovering the early osteoarthritis.

In another studies of early joint cartilage changes of dysplastic hips, the conventional x-ray technique did not discover the early joint cartilage changes whereas the dGEMRIC method did.

This is a new method that still is under development. “A number of methodological issues remain to be resolved” says the radiologists (Burstein 2003), what means that it is used on only selected clinics and that there are radiologists skeptical to this method, but as yet it seems the only methods that may discover early stages of osteoarthritis.

There are as yet no markers in the patient’s blood that could tell that the destruction of joint cartilage is ongoing.

Neither are there any genetic markers, changes in the genes, telling that the person would be more prone to development of osteoarthritis.

Information for you: You may be offered this dGEMRIC procedure to evaluate your painful joint that does not show any changes on conventional x-ray. Well exercised, the dGEMRIC procedure may help to come closer to the cause of your joint problems.

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References:

Burstein D, Gray M.: New MRI technigues for imaging cartilage. Journal of Bone and Joint Surgery - American Volume, Vol 85-A, Suppl 2, 70 - 77

T. C. B. Pollard, et al.: The assessment of early osteoarthritis. Journal of Bone and Joint Surgery - British Volume,2008, Vol 90-B, 411-421

Mars 2008

25/03/2008

GENE THERAPY FOR LOOSE TOTAL HIPS – IS IT FEASIBLE?

Loose total hip is a failed total hip that causes pain to the patient. Such loose total hip lost its once stable fixation to the skeleton; it lies enclosed in soft tissue membrane that contains cells that are progressing with the dissolving of the skeleton around the total hip device. See also the chapter Loosening of total hips.

The treatment of choice of a loose total hip is by revision operation: the surgeons opens the joint, removes the loose total hip device and scrapes out all destructive soft tissue to stop the

ongoing destruction of the skeleton. After that the surgeon places in a new total hip device.

This is a big surgery; old patients (> 80 years of age) do not tolerate it well. According to the statistics 5% of them die within 90 days of surgery and 20 % need repeated hospitalization for medical, urological, neurological, and other complications.

A method that could render the loose total hips in old patients stable again without a new operation would thus save many lives.

Such method would first dissolve the noxious soft tissue around the loose total hip and then fill the void with bone cement. By this procedure the fixation of the total hip to the skeleton will be reestablished. A fantastic idea perhaps because nobody has done it as yet. The Dutch surgeons from the university of Leiden decided to investigate the feasibility of this idea (de Poorter 2008).

They combined two methods already in use.

The one method uses infection of cancer cells with “suicidal gene” to destroy the bowel and uterine cancers. The Dutch surgeons used this method of “gene therapy” to destroy the osteolytic membrane around the loose total hip.

The other method uses injection of bone cement into the fractured vertebra to stabilize the fracture. The Dutch surgeons used the bone cement injection to fill the void that resulted after “suicide” of the soft tissue cells around the loose total hip.

They treated 12 patients (mean age 88 years !) with loose painful total hips whose condition precluded revision operation. All patients tolerated the treatment and none of them suffered complications from this treatment.

Evaluation after 6 months demonstrated that all patients had less pain and more walking capacity after this treatment.

Information for you: This is a unique trial done only in Leiden, The Netherlands. The primary goal was to establish the risks for the patients with this method. The report presents a detailed description of patient selection, patient information, and all precautions taken to protect the patients. In this way it is an excellent example how such experiments should be done.

Will it work? It is impossible to tell at this stage. In every case, preliminary examinations revealed that not all osteolytic tissue was dissolved by the gene therapy method the authors used. Control x-ray pictures showed that the void after the removed soft tissue was not filled entirely with the bone cement either.

You should keep in mind, however, that this is not a treatment method for patients who will tolerate revision operation.

If this method will render the old, inoperable patients with less pain and more function in their loose total hips, it will be a great success. These patients don’t appear in any statistics and suffer in the quiet.

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References:

dePoorter JJ et al.:   Gene Therapy and Cement Injection for Restabilization of Loosened Hip Prostheses. : Hum Gene Ther. 2007 Dec 7 [Epub ahead of print )

Department of Orthopedics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands

16/03/2008

TOTAL KNEE REPLACEMENT – IT IS THE SURGEON WHO DECIDES THE RESULT

Long term results of total knee replacement are difficult to find although the annual number of total knee replacement operations passed the annual number of total hip surgeries.

Recently published a group of British surgeons ten year results of a relatively small patient group (284 total knees) operated on with Kinemax R total knee model (Howmedica) (Cloke 2008).

This total knee model has been designed for insertion and fixation to the skeleton with bone cement. The British surgeons used in some of these patients bone cement fixation but in others no cement was used for total knee fixation “due to concerns regarding the use of cement at that time”. It is for this curiosity that this report is worth mentioning

Ten years results demonstrated that only 84% of the total knee joints survived ten years after surgery. Closer analysis namely showed that patients >60 years of age with their total knees cemented had the best results (94% of these total knee survived ten years). On the other hand, young patients (<60 years) where the surgeon did not use the bone cement fixation had the worst results, 29% of them failed within ten years!

Obviously, total knee devices developed for use with bone cement should be used with bone cement. Otherwise the patients pay the toll as the 29% failed total knees in young patients with uncemented Kinemax total knees demonstrated.

Seven years before this article a group of other British surgeons published another report on 400 operations with the same total knee model (Kinemax R). Only three percent of these patients' Kinemax total knees failed during nine postoperative follow up years (Back 2001).

Information for you: When you compare these two results achieved by two different groups of surgeons it became obvious that it is the surgeon who is responsible for the success or failure of the implant, not the implant model itself. You should choose the surgeon for your total knee replacement first hand. Even “good” total hip/knee models may fail when the surgeon does not follow the established rules.

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References:

Back DL et al: The Kinemax total knee arthroplasty. J Bone Joint Surg-Br 2001; 83-B: 359-63

Cloke DJ et al: 284 press-fit Kinemax total knee arthroplasties followed for 10 years. Acta Orthopaedica 2008; 79: 28-33

12/03/2008

SURGICAL APPROACH TO SURFACE HIP REPLACEMENT – NOT IMPORTANT

Today not only surgeons but also their patients discuss advantages and risks with different surgical approaches to the hip joint. The most known were the statistics that demonstrated that surgical approach to the hip joint from the back was associated with greater risk of dislocation if this approach was used for operation of a total hip. Successively it appeared that the bad rumors of back (posterior) approach to the hip joint was associated rather with bad operation technique then with the operation approach itself. (See also the chapter Operation total hip Approach)

This view is further reinforced in a report from British surgeons who followed 790 patients operated on with 909 surface replacement hips for at least 2 years (range 2 to 9.5 years) (McBryde 2008). One group of patients were operated by one group of surgeons who used the anterior (anteriolateral) approach (135 operations), the surgeons operating on the other patient group used the back (posterolateral) approach (774 operations). There was no difference between the patients’ characteristics in both groups.

There was no difference between patient groups for postoperative complications, patients’ satisfaction, and survival of the implanted surface hip joints.

Almost exactly equally many surface replacement hip joints survived 8 years, 97,7% operated on through posterior and 97.2% operated on through anterior approach.

Information for you: Interesting on this report is the high survival of Birmingham surface hips: 97% during 8 years. But then these patients were operated on in Birmingham, and among the authors are well known names of surgeons developing surface hip replacement surgery.

One old rule returns to mind: Choose first an experienced surgeon and he /she will choose the best approach and the best artificial hip joint model.

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References:

. McBryde CW et al: . The Influence of Surgical Approach on Outcome in Birmingham Hip Resurfacing, Clin Orthop Relat Res. 2008 Jan 26 [Epub ahead of print]

10/03/2008

FRACTURES OF THE STEM COMPONENT OF THE TOTAL HIP ARE STILL OCCURRING

I recently read on a patent support website a history of a total hip patient who had gone several months with pain in her thigh and her x-ray pictures showed “all is right” until a new x-ray picture discovered fracture of the stem component of the total hip.

It seems that some surgeons do not consider a fracture of the total hip component a possibility nowadays and their patients are suffering unnecessarily.

Yet, fractures of metallic femoral stem components happen even today and the culprit is either wrong construction or material flaw or both.

Australian surgeons published recently four cases of stem fractures of the Omnifit R model of total hip. The fractures occurred after several “years of use” (10 to 17 years after insertion of the total hip (Lam 2008).

In all four fractured stems the metallurgical examination showed material flaws at the fracture site.

Information for you: Stem fractures are a very rare event today, yet they still occur. (see also the chapter Fatigue fractures of total hip for pictures) If you have an unexplained pain in your thigh after total hip surgery, ask your surgeon to make an extra careful look at the x-ray pictures of your total hip device.

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References:

Li-On Lam et al: Catastrophic failure of 4 cobaltr-alloy Omnifit Hip arthroplasty.. Acta Orthopaedica 2008: 79: 18-21.

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06/03/2008

IS OVERWEIGHT A RISK FACTOR FOR TOTAL HIP PATIENTS?

It is an important question as increasing numbers of patients undergoing total hip replacement are overweight. Simple “common sense” of some surgeons dictated the simple rule: the more body weight the more load on total hip device; the more load on total hip device the sooner it will fail.

Dutch surgeons followed a group of 411 patients operated on with 489 total hip replacement, divided in normal weight patients (BMI =< 25), overweight (BMI>25), and obese (BMI >30) (Haverkamp 2008).

It appeared that overweight and obese patients were at greater risk for heart failure than normal weight patients. But ten year survival of total hip devices was equal in all three patient groups, being 94.9%, 90.4%, and 91% for normal-weight, overweight, and obese patients.

Also the function of the total hip at ten year control was similar in all three patient groups.

Swedish surgeon used a more convenient method to investigate whether overweight increases risk for dislocation of the total hip. They coupled together the Construction Workers Union register of health status together with the data in the Swedish National Hip register. In this way they got a group of 2 100 male patients. (Azodi 2008) operated on with total hip replacement. Their body mass data were registered in the Construction Workers Union register and the dislocation data in the National Hip register.

It appeared that 2.5% of these patients got at least one dislocation of the total hip during three postoperative years. Overweight carried increased risk of dislocation (2.5 times) and obesity 3.7 times.

On the other hand, smoking did not increase the risk of dislocation. (Why should it?)

The authors concede that their study has several “smaller” flaws, for example it was unknown whether the overweight and obese patients had also higher consumption of alcohol and whether gender was also a risk factor (only male patients were registered).

Information for you: The overweight and obese patients have equal advantage of total hip replacement and it seems that the long term results are equal for lean as well as for overweight and obese patients. The overweight and obesity, however, shorten the life of the patients and probably increase the risk of dislocation of their total hip.

Try to diminish your weight before the surgery; it is known that the hopes to diminish the weight after the surgery are only seldom full filled.

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References:

Azodi O et al, : High body mass index is associated with increased risk of implant dislocation… Acta Orthopaedica 2008; 79: 141 - 47

Haverkamp D, et al: Is the Long-term Outcome of Cemented THA Jeopardized by Patients Being Overweight? : Clin Orthop Relat Res. 2008 Feb 21 [Epub ahead of print]

February 2008

26/ 02/ 2008

A NEW PLASTIC MATERIAL FOR CUP COMPONENTS OF TOTAL HIPS

Ultra High Molecular Weight PolyEthylene (UHMWPE) has always caused problem for total hip surgeons. Several attempts to improve the wear characteristics of this material were made, some of them with disastrous results (carbon fiber reinforcement), other with lasting improvements (cross linking).

In the 1990’s German surgeons developed carbon fiber reinforced polyether ketone, a material called Caproman TM, Preliminary results published in German journals spoke about excellent wear resistance and good clinical results of cup components made from this material. Then followed complete silence.

In January 2008 published the known Journal of Arthroplasty a short report from Italian surgeons about the tissue reaction against this material observed in one patient where the component was removed because of infection Pace 2008).

The Italian surgeons working in a regional hospital say that microscopic examination “showed only a small amount of particles from the composite insert in the patient's periprosthetic tissue”.

Information for you:

Research and development of new materials for total hip devices is ongoing at many places in the world without much information leaking to outside people. I’m publishing this sketchy information in hope that there is maybe a reader who knows more.

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References:

Pace N et al: Technical and histological analysis of a retrieved carbon fiber-reinforced poly-ether-ether-ketone composite alumina-bearing liner 28 months after implantation. J Arthroplasty. 2008 Jan;23(1):151-5.

22/02/2008

REPLACEMENT OF ONLY ONE HALF OF THE KNEE JOINT – TEN YEARS RESULTS

The knee joint is a mechanically complicated joint. Only one part of joint surfaces may be worn out, whereas a greater part of the knee joint area may still have well retained cartilage coverage. See also the chapter Total knee operation.

For these patients it suffices to replace only the areas with worn cartilage; such operations is called “Unicompartmental Knee Arthroplasty”.

There is still discussion ongoing if such smaller operation may bring lasting relief for these patients.

Two American surgeons published recently a carefully done review of 55 such Unicompartmental knee arthroplasty operations done in 51 patients (Emerson and Higgins 2008) who were followed for 12 years.

After 10 years, 85 % of all replaced knee joints were still in place and functioning. 6 ( 11 %) unicompartmentally replaced knee joint failed because the cartilage in other areas of the operated on knee joint also wore out. These patients got the whole knee joint replaced with a total knee joint.

Information for you: The results of these relatively young patients (mean age 64 yrs) operated on with the unicompartmental knee replacement demonstrate that the mechanism of the replacement device will last over ten years. Note that the absolute majority of knees in patients who needed revision operation failed because of progression of wear out of joint cartilage. It is also possible that this progress was on the way when the surgeon implanted the unicompartmental device, but he/she did not recognize it.

This report too confirms the current “consensus” that replacement of only one knee joint chamber is indicated when the knee joint has good ligament stability and good cartilage cover in other knee joint chambers.

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References:

Roger H. Emerson, and Linda L. Higgins,: Unicompartmental Knee Arthroplasty with the Oxford Prosthesis in Patients with Medial Compartment Arthritis. The Journal of Bone and Joint Surgery (American). 2008-Am; 90-A: 118-122.

20/02/2008

TWENTY YEARS OF IOWA TOTAL HIP MODEL

American surgeons in Iowa developed for twenty years ago a cemented total hip that got the name “Iowa total hip”.

Recently, they published results in patients who were operated on with this total hip model twenty years ago. It appeared that 82 % of all patients still had a functioning total hip joint in place. Thus, less than 1% of all total hips failed annually; a very good result, better than the benchmark.

Will you have this total hip model for replacement of your painful hip joint? You can’t. This total hip joint model is no longer available on the market.

Information for you: This is one of the many curious cases that make the situation on the total hip market so confused.

Whereas for the majority of total hip models that are available to the surgeon today there are no known results, the past total hip models with proven good results are no longer available.

One wonders what is the goal of churning steady new, unproven models of total hips on the market.

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Reference:

John J. Callaghan et al.: Total Hip Arthroplasty with Cement and Use of a Collared Matte-Finish Femoral Component. Nineteen to Twenty-Year Follow-up . The Journal of Bone and Joint Surgery (American). 2008;90:299-306.

16/02/2008

BIRMINGHAM SURFACE HIP – THE MOST SUCCESSFUL SURFACE HIP REPLACEMENT MODEL IN AUSTRALIA?

The Australian surgeons created in 1999 a very effective National Joint Replacement Registry that is now producing interesting data. From the 2007 report it appears that surface hip replacement accounts for 8% of all hip replacement operations in Australia.

The majority (75%) of all surface replacement operations in Australia were done with the Birmingham Hip Resurfacing system. The rest of the resurfacing system comprises further four systems with only a few hundred of operations each. Moreover, only three resurfacing systems in this statistics have five years follow up results data: Birmingham Hip Resurfacing (Smith & Nephew), Conserve Plus (Wright), and Cormet (Corin).

During these five postoperative years failed 3.7% Birmingham Resurfacing Hips, 16.7%! Conserve Plus hips and 7.4% Cormet hips.

Obviously, Birmingham Hip Resurfacing system has best results, within accepted benchmarks. But this is so only because the other two surface hip systems have results that are catastrophically worse.

Information for you: In this statistics the Birmingham Hip Resurfacing system has good results lasting five years after surgery. Statistics is based on mixed data from both university clinics and small country hospitals. It means that one can expect that an “average” orthopaedic surgeon would also come close to these good results with the Birmingham Hip system. Five years is, however, a relatively short observation time.

Five year results with the other two systems are simply catastrophic in this statistic. There are no details in the annual report to explain them. Probably it would be best to disregard these results. With nothing to compare with, the preeminence of the Birmingham Hip system thus disappears. Based on this Annual Report one thus can say that Birmingham Hip system proved a good surface hip system in Australia but nothing more.

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References:

http://www.dmac.adelaide.edu.au/aoanjrr/publications.jsp?section=reports

BHR has “highest survivability rate according to Australian Registry figures. European Orthopaedic Product News. January 2008, 11.



14/02/2008

“STITCHED IN” SILVER INTO THE SURFACE OF TOTAL JOINTS TO PROTECT THEM AGAINST THE INFECTION

Patients with bone cancer may have the whole bone that is destructed by cancer (thighbone for example) removed and replaced by a large artificial joint that replaces the removed thighbone and the adjacent joints (hip and knee joints). Such mega-prostheses as these artificial joints are called have, however, large surface area that attracts bacteria. Thus, ´risk of infection is 11% for cancer patients operated on with these mega-prostheses, which is twenty times higher risk of infection than for patients who have their total hip replacement surgery done for wear of their joints.

The British manufacturer of the custom made mega-prostheses, Stanmore Implants Ltd, is thus collaborating with a company (Accentus Medical) that specializes with putting silver onto surface of these mega-prostheses.

Silver is a metal with known capability to kill the bacteria that are causing infections around the total joints. Silver was used for sterilization of water in the pace shuttle and silver is incorporated into the surface of carbon heart valves to prevent bacterial colonization of the valves.

Putting silver into the surface of the mega prosthesis is not like silver plating. Silver plating was proved in the past and was abandoned because it caused toxic damages locally on the tissues.

The new technique is called surface modification process. It puts small pits filled with silver onto the surface of titanium made mega –prostheses. From these small pits leaches silver ions in just right concentration to kill the bacteria that may land on the surface. On the other hand, the concentration of silver ions is not too high to cause toxic damage to patient’s tissues.

As yet, there are 31 patients with these “surface modified” mega-prostheses. The technique is applicable only for implants made from titanium and its alloys.

Information for you: This report just shows that there is steady progress in the science of artificial joints. This silver protection technique is just now applicable for a very small group of patients only, but if it will show positive effect it may be successively applied also for “conventional” total joints (hips and knees). Until then there are several questions to be answered. For example: How long will the protective effect of the leaching silver ions last?

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References:

Accentus Develops Surface Modification technology. European Orthopaedic Product News, January 2008, 10

January 2008

25/01/2007

OBESITY NO OBSTACLE TO SURFACE HIP REPLACEMENT

Many obese patients were denied in the past surface replacement of their painful hip joints because their surgeons feared that their increased body weight will knock the replaced hip.

Fracture of the femoral neck is a rightly feared complication of the surface hip replacement. See for details in the chapter Surface hip replacement. There is, however, no proof that increased body weight causes fracture of the surface replaced neck of the thigh bone.

Recently, professor Amstutz and colleagues from the Joint Replacement Institute in Los Angeles, USA, published a comprehensive study that will dispel similar fears (Le Duff 2007).

They followed a group of 651 patients, operated on with surface hip replacement for at least two years after surgery. 531 patients made a so called control group; they had Body Mass Index (BMI) < 30, which is the lower limit for obesity. 120 patients were obese, their BMI was >30. See the chapter Obesity details for more info.

During the follow up period there appeared fractures of the operated on the femoral neck in both patient groups. There were "only" 1.4% femoral neck fractures in the obese patient group and almost four times as much (5%) neck fractures in the non obese group. It thus seemed as if obesity protected the obese patients against femoral neck fracture!

Now, in the control group of 531 patients there were a lot of overweight patients, with BMI between >25 and 30 .

To see if the increased body weight really protected the operated on patients against the femoral neck fracture the authors divided all 651 patients into three weight class groups according to their BMI: normal weight patients with BMI <25, overweight with BMI 25 to 29, and obese patients with BMI 30 . It appeared that the risk of femoral neck fracture really was dependent on the patient’s body weight. The risk of failure of the surface replacement wasfound to have decreased twofold from one group to the next asthe body mass index increased.

Interesting also that there were not more other complications, such as infection or deep vein thrombosis in the obese patients.

Are there no disadvantages for the obese patients to have surface hip replacement?

Yes, there are a lot of them. The postoperative mobilization and rehabilitation of the obese patients was much more slow procedure and the final functional achievement of these patients was lower then the final functional state of the replaced hips for the lean patients.

Then, this was a relatively short time observation. Nobody can exclude that the obese patients may have more failures of their surface replacement by late loosening.

So the authors conclude their study with a cautious statement “ At this time, we believe that a body massindex of 30 is not a relative contraindication to resurfacing.However, weight reduction should still be encouraged to facilitatethe procedure and enhance the clinical results”

Information for you: If possible loose your body overweight before your surface / total hip replacement. The protective effect of obesity on the risk of postoperative fracture after surface replacement is no miraculous advantage; it is caused by two factors.

First, obese patients have much stronger skeleton than their lean colleagues. First, They produce in their fat tissue special hormone that makes their skeleton stronger, to be able to bear the increased body weight. Body motion will have the same effect on the lean patients.

Second, the obese patients move much less than their lean colleagues; they put less load on their newly operated on skeleton. The lean patients do not overload their skeleton either because their low body weight.

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References:

Michel J. Le Duff et al.: Metal-on-Metal Hip Resurfacing for Obese Patients. The Journal of Bone and Joint Surgery (American). 2007;89-A :2705-2711.

21/01/2008

LOW WEAR OF CERAMIC TOTAL HIPS FIVE YEARS AFTER SURGERY

Australian surgeons published a report about results of ceramic on ceramic total hip operations which demonstrates that technically simple total hip constructions may be all what is needed for good results (Lusty 2007).

They followed 283 patients who were operated on with 301 ceramic on ceramic total hips. The cup component of this total hip is produced by Stryker Osteonics and is called Osteonics ABC^TM.

The results were really spectacular: Seven years after surgery, 96% of all total hips were still in place and function. Only one patient showed signs of osteolysis (and was operated on anew), but five patients were operated on anew because of fracture of the thigh bone around the femoral shaft component and four patients needed new operation because impingement of the iliopsoas tendon.

The authors see reasons for these two failure modes: First, the instruments for broaching the femoral marrow cavity were too large and damaged the skeleton too much. The authors developed smaller ones.

Second, the cups were protruding too much and encroached on the iliopsoas tendon. I believe that these cups, although of simpler construction were still too large.

With respect to the recent critique of the Stryker manufacturer from the USA agency for control of orthopaedic devices (FDA) this article is very interesting.

The cup component (Osteonics ABC^TM) evaluated by the authors in this article is composed of two shells:

The picture shows cross section through two models of ceramic cups. The left side picture shows the Osteonics ABC^TM cup component. You see that the cup is composed of only two shells; the inner ceramic shell (in-liner) is recessed within a metallic back up. The elevated rim of the metallic back-up is protruding to prevent damage to the ceramic or scoring ofthe femoral neck if impingement occurs. This cup is produced by Stryker Osteonics.

This Osteonics ABC cup model was, according to the authors, easy to put in place and the ceramic in-liner was not at risk for chip fracture. Obviously, the protruding rim construction was enough for protection of the ceramic.

On the right side picture you see the criticized TridentTM cup model produced also by Stryker. Note the difference between the two cup models. the much simpler Osteonics ABC^TM  and the complicated TridentTM.

The complicated construction of the Trident cup made it difficult for the surgeon to put all cup components together on the operation table. Not only that, it was also difficult to produce all three cup components with right dimensions. This is a typical example of the engineering rule “when you improve it to much it will not work”.

Information for you: The measurement of wear could be made only on cups removed at revision operations. Even on these cups the wear of the ceramic material was only 0.2mm3 annually; about hundred times less than the wear of the conventional metal on polyethylene total hips. And no fractures of ceramic material occurred. These are “encouraging” news.

This is, however, still relatively short time observation – 7 years maximally. But this observation confirms the previous positive results. The ceramic total hips wear little and become loose seldom. But their cups are bulky and cause soft tissue problems (iliopsoas impingement).
Only one of the all 283 patients had a squeaking ceramic hip. He learned to rotate the leg so that the squeaking ceased. Obviously, squeaking need not to be a problem in ceramic total hips.

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References:

P.J. Lusty et al: Third-Generation Alumina-on-Alumina Ceramic Bearings in Cementless Total Hip Arthroplasty. The Journal of Bone and Joint Surgery (American). 2007;89-A :2676-2683

18/01/2008

STRYKER’S CERAMIC HIP TRIDENT RECEIVED WARNING FROM FDA

The second biggest manufacturer of artificial hip joints, Stryker, got a warning from the USA agency for the defective quality of total hip devices produced by the Company.

In the letter that was published on Agency’s Webbsite January 17, the Agency points specifically to the defects of the Company’s ceramic cup component Trident^TM. (Click here for picture of the Trident cup. It is the upper picture)

There were ongoing complaints that this cup is difficult to assemble and to anchor stably in the patient's skeleton since 2005. Moreover, the patients complained about noises from these cups, the noises that sometimes heralded looming failures. The Agency states that Stryker Company “had failed to correct the identified faults”. Several letters were namely sent by the Agency during 2007 urging the Company to correct the manufacturing faults that led to the reported failures of the Trident component.

Interesting reading that evokes some questions:

First, the letter contains no data about the number / percentages of the Trident cup failures. How big is the problem really?

Second, the timing of the Warning letter. It was sent on Nov 28, 2007, yet it was published on Agency’s Webbside almost two months later (January 17). Why this delay?

Third, the Warning Letter speaks about the failure of the Trident ceramic cup leading to new operation (revision). How much was published about it in the scientific journals?

Practically nothing. The Trident cup is a complicated construction, consisting of three layers (See Ceramic Total hips). It was introduced as “The right implant for the right performance”.

Surgeons working for Stryker published a report in 2005 about the Trident component. Six USA surgeons followed 316 patients who were operated on with the Trident cup. Three to five years after surgery these surgeons noted that in these patients the ceramic in-liners remained intact during this period. The surgeons concluded “Encasing the alumina ceramic insert in a titanium sleeve seems to have resolved the issue of insert chipping on impaction and supports the continued use of Trident bearings in relatively young patients”.

In March 2007 independent British surgeons published a report that came to completely different conclusion. They found that it is difficult to place properly this Trident cup. (Click here for a report about this article). The British surgeons suspected that the difficulty to place the Trident cup properly is caused by the fact “that the Trident shell deforms upon implantation, thereby preventingcomplete seating of the liner”. And they conclude “ We have identified a potential problem with the Trident ace-tabularshell when used in combination with its metal-backed ceramicliner”.

The FDA letter, however, offers another more probable explanation of “this potential problem. The “adulterated methods used for manufacturing of Trident cup” are producing components with wrong dimensions, incompatible with each other. It is then impossible to assemble properly the Trident’s three cups together. Because these cups are recommended for use in young patients so that these Trident cup are supposed to stay in place several years, this is a serious fault.

Information for you: It is always difficult to explain why the doctors working for the manufacturing company find better results for the products already on market than independent surgeons. The suspicion that company’s surgeons are forbidden to publish bad results, often presented in lay press, is not much probable. If the product is already on the market, the bad characteristics of the product cannot be kept secret.

In my opinion Stryker Company should finance the American surgeons (doctors D’Antonio and colleagues) who authored the 2005 article to do a new comprehensive review of these patients. They should do new x-ray pictures of Trident cup components and assess the placement of the components. They should also evaluate the occurrence of squeak sounds and the possible relation of the squeaks to the looming failure of the cup.

There are many patients bearing Trident cup component in their artificial hips. These patients are anxious about the fate of just their Trident cup; Stryker Company has the ethical obligation to still the anxiety of these patients.

According to the information recently published by Dept of Justice; Stryker paid 27 million $$ to doctors working for the Company. Some of the money was probably paid also for the development of the Trident cup component. There is thus all reason to finance this second study of the Trident cup components.

On the other hand, we should be reasonable. FDA issues several warning letters annually to different companies; only seldom is the fault of the product so big that the product is retracted from the market. The idea behind the Trident ceramic cup is great and it will work if the manufacturing process would follow the Current Good Manufacturing Practice.

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References:

. D'Antonio JA et al.: A titanium-encased alumina ceramic bearing for total hip arthroplasty: 3- to 5-year results. Clin Orthop Relat Res. 2005 Dec;441:151-8

A. J. Langdown, et al: Incomplete seating of the liner with the Trident acetabular system, A CAUSE FOR CONCERN? Journal of Bone and Joint Surgery 2007 - British Volume, Vol 89-B, 291-295.

12/01/ 2008

INCREASED RISK FOR CANCER AFTER METAL / METAL JOINT ARTHROPLASTY IN PATIENTS WITH INFLAMMATORY DISEASES?

The Swedish Professor Lars Lidgren at University in Lund points to the known fact that patients with rheumatoid arthritis and other chronic inflammatory diseases have twice increased risk for cancer of blood cell system (Lidgren 2008). A specific form of this cancer called malignant lymphoma is typical for patient with rheumatoid arthritis, lupus erythematosus, and other inflammatory diseases.

The author goes through the studies, published in the past that investigated the risk of cancer after total hip and total knee replacement. Some of these studies demonstrated that risk of blood cell cancer was increased in patients operated on with total joints compared with general population; other studies did not find any such risk.

Only one such (Swedish) study investigated separately patients who were operated on for osteoarthritis and for rheumatoid arthritis in their knee joints.

This study found that patients with rheumatoid arthritis who had their knee replaced had four times higher risk for blood cell cancer than people in the general population. No such risk was observed in patients operated on for knee osteoarthritis.

In the past there were also published studies mainly from Finland that found increased risk of blood cell cancer after the old metal on metal total hips.

There are also studies demonstrating that patients with metal on metal total hips have changes in their blood cells and immunological system.

Professor Lidgren concludes from these studies that “Immunological high-risk factors for patients undergoing metal-on-metalimplantation are therefore advanced RA, systemic chronic inflammationof connective tissue, ongoing anti-TNF treatment,..”.

The author also says that the data assembled in the National Registers should be used to study whether the total joint replacement, especially with metal on metal devices, really increases the risk of cancer in patients with general inflammatory diseases.

Information for you: This is an important article because it shows the issue of total joint and cancer in a new perspective. It is probable that the previous cancer studies were not specific enough. It is possible that only patients with specific diseases (inflammatory, for example) are at increased risk of cancer after total joint replacement

Only about 5% of patients operated on with total hip and/or total knee have rheumatoid arthritis. Many of them are also young. Yet, as this article shows these patients are not candidates for any form of metal on metal joint replacement device.

See also the chapter: Total hip and cancer.

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References:

Lidgren L.: Chronic inflammation, joint replacement and malignant lymphoma. Journal of Bone and Joint Surgery - British Volume; Vol 90-B: 7-10.

04 / 01/ 2007

CUP COMPONENT FROM A NEW POLYMER MATERIAL MAY MAKE POLYETHYLENE REDUNDANT- A BREAKTHROUGH?

Over 40 years the polyethylene was the practically only one material used for manufacture of bearing surfaces of artificial joints. Some attempts to replace the polyethylene with other polymer materials (Delrin, Teflon) ended in catastrophe.

It thus seems surprising to find a small and relatively unknown company to use a new polymer material instead of the conventional polyethylene for manufacture of cup components for total hip prostheses. The surprise only demonstrates that the majority of orthopaedic surgeons know so little about new developments of artificial joints that is going outside the biggest manufacturers.

The AIC Company (Active Implant Corporation), which is located in the USA (Memphis, Tennessee) and also in Israel, had produced the novel cup component (The Tribofit^TM Acetabular Buffer cup component) from polycarbonate urethane (polyurethane). The cup component has been approved for use already in the European (EU) countries.

Acetabulum Buffer Cup TM (AIC Company' brochure)

On this picture you see the TurbofitTM cup on the little picture; on the larger picture you see that the polyurethane cup is used just like the conventional polyethylene cup. It is placed inside the metallic back-up. However, it cans be also placed directly into the reamed socket (Press-fit fixation)

The x-ray picture in the background shows a healthy hip joint with a cartilage layer and a narrow line in the middle between them. This is the line occupied by a thin layer of joint fluid placed between both joint bearing surfaces.

The x-ray picture should remember that the new polyurethane cup component allows similarly low friction and wear as natural cartilage thanks to very good wetability of polyurethane material. The polyurethane attracts liquid to its surface, thanks to these characteristics there is always a thin layer of liquid on the polyurethane cup’s surface. This layer diminishes wear and friction of the polyurethane cup component.

This material has been in use for medical products (hearth valves) already for several years and its biocompatibility is well established. Now, this material, with mechanical and friction characteristics close to the natural joint’s cartilage is seeking its way into the construction of artificial joints.

At the combined meeting of Orthopaedic Research Societies in Honolulu, Hawaii, Doctor R. Smith, from Campbell’s Orthopedic Clinic, Tennessee, USA presented some interesting characteristics of this polyurethane material.

The bearing surfaces made from this material wear six times less than surfaces made from the conventional polyethylene. Polyethylene is 70 times harder than joint cartilage, the pliable polyurethane that is equally "soft" as the joint cartilage. Moreover, the polyurethane wear particles do not attract bacteria that occasionally are traveling through blood even in otherwise healthy patients. Polyethylene wear particles, on the other hand, are often colonized by these bacteria.

According to one theory, such bacterial colonies located on polyethylene wear particles, even when quickly destructed by the patient’s body, may leave bacterial toxins on the surface of the particles. These polyethylene particles with adherent bacterial toxins are then the real cause of dissolving bone disease (osteolysis). The osteolysis then leads to eventual failure of the total hip by “aseptic” loosening. No living bacteria can be proven in such patients. Laboratory tests demonstrated that the number of the polyurethane wear particles with adherent bacterial toxins is six times lower than the number of similar polyethylene wear particles.

If these characteristics of the polyurethane will be reconfirmed by other laboratories this material would really replace the currently reigning polyethylene in construction of artificial joints.

Information for you: The report about the new polyurethane appeared in the minor journal European Orthopaedic News in November 2007. None of the big orthopaedic journals had a notice. Yet small, individual reports about this “novel” material were appearing since 2000 as a I found after much searching (Smith 2000). The last report appeared in 2007, also in a less known journal (Scholes 2007). This can be a real breakthrough, just watch for continuation of the story.

There are, however, also some not fully explained facts. Much of the development was obviously done in England (Leeds, Durham), yet the present research is done in the USA (Memphis, Tennessee). But, the finished product is marketed on the European Continent and got already the EU approval.

Third, the theory that the real cause of total hip loosening are polyethylene wear particles with attached bacterial toxins is still only theory. Certainly, bacterial toxins after dead bacteria were found on polyethylene wear particles, but as yet there is no proof that it is just this combination of wear particles plus toxins that causes osteolysis.

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References;

Smith RM et al: A tribological study…. J Biomed Mater Res 2000;53: 710-15

Scholes J et al.: Polyurethane Unicondylar Knee Prosthesis Physics in Medicine and Biology 2007; 57: 197 -212

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02/01/2008

MINIMALLY INVASIVE TOTAL KNEE SURGERY – BEST WITH COMPUTER ASSISTANCE

Total knee surgery done through minimal incision surgery (MIS) approach is still not practiced by many surgeons and did not achieve such popularity as MIS for total hip replacement.

Generally, correct placement of the total knee joint through minimal incision is not easy. The lower leg has a mechanical axis, a straight line going from the center of the hip joint through the centre of the knee joint to the centre of the ankle. This mechanical axis is often distorted by knee joint disease. One of the goals of total knee surgery is restoration of this mechanical axis. See also the chapters Total knee operation and Computer assisted total knee surgery.

This is not easy in surgery done through conventional approach and it is much more difficult when the surgeon uses a very small wound (MIS) for approach into the knee joint.

A group of surgeons working in Singapore’s National University Hospital studied how use of computer navigation systems influences the accuracy of the placement of the conventional total knee device when the surgeon uses the MIS approach ( Dutton 2008).

There was one group of 56 patients who had their knee joint replacement done through the conventional surgical approach without the use of computer assistance and a second group of 52 patients where the surgeon used computer assistance to place the total knee device through the minimal incision (MIS) approach.

The patients were followed up after surgery for 6 months just now. (The follow up will continue).

The x-ray study revealed that the surgeon succeeded to restore the mechanical leg axis in 92% of total knee replacements done with computer assistance, in spite of the fact that this surgery used minimal approach.

On the other hand, in patients operated on without computer assistance, the surgeons succeeded to restore mechanical axis in only 68% of operations, in spite of the fact that the surgeons used a large conventional approach with good visibility of the knee joint.

The computer assisted group had 20 minutes longer operation time, but this had no influence on the speed of recovery. These patients left the hospital one day earlier (after 3 postoperative days) than patients operated on with a conventional approach. Also the initial recovery of knee joint function was quicker in patients operated on through MIS approach; after six months, however, the function was equally good in both patient groups.

Information for you: MIS approach for total knee replacement surgery seems to give few advantages; you nay leave the hospital one day earlier but the advantage will disappear after some months.

What seems more important is the improvement in the accuracy of surgery that appears with the use computer assistance. If more such studies would show similar results, one should demand that all total knee replacements should be done with computer assistance.

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References:

Andrew Quoc Dutton et al: Computer-Assisted Minimally Invasive Total Knee Arthroplasty Compared with Standard Total Knee Arthroplasty. A Prospective, Randomized Study . The Journal of Bone and Joint Surgery (American). 2008;90-A:2-9.

December 2007

29/12/2007

SURFACE HIP REPLACEMENT DEVICES ARE ROCK STEADY FIVE YEARS AFTER SURGERY.

Modern surface hip replacement uses only metal bearing surfaces for both hip socket and femoral head replacement. Probably this material change can explain why the modern surface hip replacement, which came seriously into life about 1995, is so successful.

Swedish surgeons measured how stably anchored are the surface replacement devices after five years. They used the very accurate x-ray measurement technique developed in Sweden. The RSA (RadioStereophotogrammetric Analysis) is a tool that that measures the migration of the total / surface hip implant with a ten times greater accuracy than can be done on the usual plain x-ray pictures. In the study participated also English surgeons doctors D. J. W. McMinn and J. Daniel from The McMinn Centre, Birmingham, England.

On 19 surface replaced hip joints they found that these devices practically did not change their rigid anchoring during the five years after surgery.

It is known from the total hip surgery that devices that remain steadily anchored so long time after surgery do not become loose afterward.

Although not absolutely guaranteed, this observation would suggest that there should be no problems with loosening of surface hip replacements even after longer periods than five years after surgery.

Information for you:

This is one of the many new reports that show good mid-term results of the surface hip replacement. This hip replacement method is patient dependent, meaning that not every patient is a candidate for it, but suitable candidates should consider this replacement technique seriously.

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References:

Itayem R. et al: A five year radiostereometric follow-up of the Birmingham Hip Resurfacing arthroplasty. J Bone Joint Surg-Br 2007; 89-B: 1140 – 3



27/12 2007

YOU MAY HAVE BOTH HIPS SURFACE REPLACED AT ONE STAGE

Patients considered suitable for surface hip replacement often have painful both hip joint that need replacement. The patients suitable for surface replacement are often active young individuals for whom two successive operations for every hip joint means too long period of inactivity. These patients would gain if both hips could be replaced at one stage instead of doing two operations with some weeks or months interval in between.

There was, however, conflicting experience with one stage total hip replacement, and as yet no experience how risky it was to surface replace both hips in one stage.

Now, there is a first report that says that surface replacement of both hips in one stages has “benefits for the patient and the hospital without additional complications”.

Surgeons at The Royal Orthopaedic Hospital in Birmingham, England studied 92 patients who have both hip surface replaced. In 37 patients both hips were replaced during one stay (and one anesthesia) at the operation room. This is so called one-stage bilateral surface hip replacement.

55 patients have had every hip surface replaced at two different stays (and two anesthesias) at the operation room. First when the operation wound healed after surgery on the first hip the surgeons proceeded with the operation on the second hip. This was the two-stage bilateral surface hip replacement.

The volume of blood transfused to patients was almost equal for patients in both groups (1.6 blood units in the one-stage group and 1.4 blood units in the two-stage group).

The frequency of complications during operation was higher in the two stage group (4/57 = 7%) whereas no such complications (= 0%) were observed in the one-stage group. Statistically this difference was not significant because there were too few operations in both compared groups.

On the other hand, the systemic complications (bowel paralysis, high heart rate = tachycardia) was more frequent in the one stage group (1.8% of all patients) compared with 0% complications in the two stage group. Again, no statistical significance, too few patients

The total length of hospital stay and the total cost of both operations was significantly higher for the group of two-stage patients.

Information for you: If you need both hip replaced and have reasonably good health (the narcosis doctor will assess that) there seems that one stage operation of both hips will spare your time (and the costs too), whereas this proceeding will not increase the risks.

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References:

McBryde CW et al.: One- o two- stage bilateral meral on metal hip resurfacing arthroplasty. J Bone Joint Surg-Br 2007; 89-B: 1144 – 8

November 2007

24/11/2007

FRACTURES AROUND THE TOTAL HIP – CAUSE FOR CONCERN

Although fractures of the thighbone around the total hip are still rare, they are difficult to treat. Swedish surgeons reviewed 320 such fractures that were registered in the Swedish National Hip Registry (Lindahl 2006).

They presented they findings to the Conference of European orthopedic surgeons one year later (Florence in Italy, May 2007) and the OrthoSupersite referred it its October Web issue. Identical information was thus presented three times. It must thus be important issue. Yes, it seems to be

Swedish surgeons found that the number of fractures around the total hip is increasing. These fractures appear around total hips that are sitting loose. The mechanism of these fractures is simple: The ongoing osteolysis weakens the skeleton so that there is only a thin shell left. It then suffices with minimal trauma and the bone breaks. For more information see also Other TH complications / Fractures.

The fractures around the total hip were not a frequent complication in the Swedish experience: Only 0.4% of all total hips operated on in Sweden suffered this complication. Yet, operative reparation of a broken bone around the total hip was the third most frequent cause to revision operation (responsible for 9.5% of all revision operations. Only loosening (responsible for 60%) and repeated dislocation (responsible for 13%) were more frequent reasons for revision operation.

The Swedish surgeons do not like the cementless total hips. So the absolute majority of the patients registered in the Swedish National Hip register have some type of cemented total hip. The authors found that two types (Charnley and Exeter total hip models) were more prone to suffer fracture than other models (Lubinus total hip model). So this observation would probably be valid only for Sweden.

Revision operation of bone fracture caused by osteolysis around the total hip is a difficult operation. The authors thus recommend that all patients with x-ray signs of osteolysis should be routinely followed up with x-ray examinations to discover such fracture early on.

Information for you: In other countries than Sweden (USA) the absolute majority of patients have their total hips uncemented. It is known that uncemented total hips suffer osteolysis more often than cemented total hip, although the osteolysis appears relatively late (8 and more years after surgery).

So for these patients is this information important.

For these patients it would be then important to make x-ray controls 8 and more years after surgery. Fracture of the weak skeleton may appear first as a hair-fine line and causes only pain to the patient.

It is important that the surgeon discovers the fracture at this stage, before the fracture line spreads and causes a severe damage to the skeleton.
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References:

Lindahl H et al: Three hundred and twenty-one periprosthetic femoral fractures. J Bone Joint Surg- Am 2006; 88-A: 1215- 1222

06/11/2007

ANOTHER “BONE SPARING” TOTAL HIP MODEL FAILS – WHY THROW AWAY THE MONEY?

Replacement of the hip joint with a total hip device sacrifices too much of the thigh bone. See the chapter Surface hip replacement.

There are surgeons who wished to minimize the loss of bone and developed total hip devices with short shaft components. The shaft component of these models occupies only a small upper part of the thigh bone’s marrow space.

One such total hip model is currently produced and used in Germany. (CUT total hip, ESKA Implants Company, Lübeck, Germany).

It is a cementless total hip with surface made from spongy metal (titanium alloy). On this picture (left side) you see the CUT total hip model covered with spongy metal (titanium alloy). The end of the shaft has a curiously bent form. The bent ending of the shaft is supposed to repose on the thick bone (corticalis) of the upper thighbone.

On the x-ray picture (right side) you see that the voluminous shaft component occupies the whole bone marrow space of the neck and with its “tail” reaches into the upper part of the thigh bone. It rests on the strong corticalis bone.

CUT total hip (ESKA Implants). Left: the total hip device; Right: the x-ray picture

The first positive results with this total hip model were published in a German, not indexed, orthopaedic journal in 1999 and the total hip model was released for general use. Recently the German surgeons published a report demonstrating that “the medium-term survival with this type of femoral component is unsatisfactory with a high rate of aseptic loosening” (Ender 2007). Actually 15% of all operated on CUT total hip models failed within 5 years.

Information for you: Yet one more example of a total hip model developed probably in the armchair. The bulky shaft component of this model does not spare any bone tissue at all. On the contrary, when loosening with osteolysis appears, too much bone tissue will be destructed.

Failure rate of modern cementless total hips is <5% for a 5 years period. The CUT model has three times higher failure rate. It is difficult to see any advantage in development of this probably very expensive total hip model. Such models and their development deprive money from many more patients that could be helped with more "regular" total hip devices.

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Reference:

Ender S. E. et al.: Cementless CUT femoral neck prosthesis: Increased rate of aseptic loosening after 5 years. Acta Orthoped 2007; 78: 616-21

02/11/2007

WHAT ARE THE ADVANTAGES OF MINIMALLY INVASIVE APPROACH IN TOTAL KNEE SURGERY?

It depends on what you are studying. Northern Ireland surgeons in the well known Gait Analysis Laboratory, Musgrave Park Hospital, Belfast, Northern Ireland studied whether the walking ability early after total knee surgery is influenced positively in patients operated on with MIA – Minimally Invasive Approach. Comprehensive gait analysis was done on two groups of patients, one group received their TKA through MIA and the other one received TKA through conventional large approach. Measurements were done two days after surgery.

Comparison of results demonstrated that the walking ability in both patient groups was not influenced by the operation technique (Bennett 2007). Conclusion, in spite of less operation trauma, MSI approach does not improve patient’s walking ability compared with conventional operation technique.

On the other side of the globe Japanese surgeons from Kyushu University, Fukuoka, Japan wanted to clarify whether the minimally invasive approach had an advantage over the standard approach in total knee surgery, producing better muscle strength, less pain, shorter postoperative recovery, and better clinical results in patients operated on with this technique (Tashiro 2007).

Again, the Japanese surgeons studied two groups of patients who received identical total knee device, the one group operated on with MIA, the other group operated on with conventional surgical approach.

Comparison of results demonstrated that patients operated on with MIA regained muscle force earlier, regained greater range of movement, and suffered less postoperative pain. Moreover, there were no serious postoperative complications in either group.

Comparison of x-ray pictures of replaced total knees also demonstrated that the precision of placement of total knee devices was not worse in the MIA groups.

Information for you: From these reports it seems that you may not be better walker in the first days after total knee surgery if your surgeon used MIA in your case. But you will certainly have less postoperative pain and will regain muscle force in your thigh musculature earlier.

Be prepared, however, on considerably longer stay on the operation room. The operation time for Japanese patients operated on with MIA was 56 minutes longer than operation time for patients operated on through conventional approach.

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Reference:

Bennett D et al: Comparison of immediate postoperative walking ability in patients receiving minimally invasive and standard-incision hip arthroplasty a prospective blinded study. J Arthroplasty. 2007 Jun;22(4):490-5. Epub 2007 Apr 20.

Tashiro J. et al: Minimally Invasive versus Standard Approach in Total Knee Arthroplasty Clin Orthop Relat Res. 2007 Aug 2 ;Publish Ahead of Print [Epub ahead of print]

October 2007

25/10/2007

A NEW, BONE SPARING TOTAL KNEE MODEL – BUT WHAT ARE THE RESULTS?

There is a clear trend in total joints surgery these days: As younger and younger patients need replacement of their damaged joints, especially those of the hip and the knee, the surgeons are trying to spare as much as possible of the undamaged parts of the joint to be replaced and to choose the most sparing way how to do the replacement operation.

One such example is the new total knee joint model that replaces only the knee joint spaces on the inner (medial) site and also the space between kneecap and the thighbone. The model was developed by a group of American surgeons, the head of the group, doctor Lindsay Rolston works at Henry County Center for Orthopedic Surgery and Sports Medicine, New Castle, Ind., USA (Rolston 2007).

These surgeons observed that in about 70% of their younger patients with osteoarthritis of the knee joint, there is engagement of only the inner and the frontal compartment of the knee joint. See the chapter Outline of total knee prosthesis for anatomical details.

Replacement of only inside of the knee joint with the so called unicompartmental knee joint was often not enough, because also the patellar space was engaged. On the other hand, replacement of the whole knee joint in these patients with a large total knee prosthesis has been too much. These young patients had after total knee replacement diminished function if their total knee and were more often dissatisfied.

The obvious solution was to develop a total knee joint that would spare knee joint ligaments and replace just only the damaged surfaces: the surface on the inside and the one in the front. Its name of this new total knee is Journey Deuce. Don’t ask me why Journey, but the term Deuce is related to the term Bilateral.

So here looks this newly developed bicompartmental total knee joint like: On the model of the total knee (lower row) you see the large metallic area placed in front of the knee joint which makes the articulation with the kneecap. You see also the ordinary articulation surfaces placed to replace the inside of the knee joint surfaces.

In the upper row you see to the left the photograph of the Journey Deuce total knee in place; to the right you see the schematics of the replaced knee joint (right knee joint) with replaced frontal and inside of the joint.

Journey Deuce bicompartmental total knee. Pictures courtessy Smith&Nephew and Doctor Rolston

According to doctor Rolston’s personal message, overall 600 Journey Deuce total knee models were implanted worldwide in the last 14 months with very good results.

Doctor Rolston implanted over 200 Journey Deuce total knees personally during the last 4 years, with no revision operation as yet. 80% of his patients stay in the hospital only 2 or fewer days, thanks to special mini-invasive operative technique.

Information for you: This is one new total knee model that is right in time. As with all new models, however, there are no published results as yet. This is not a new total knee model for everybody, this is a model for few selected.

First, this total knee model is not for patients with joint damage caused by inflammatory diseases.

Second, this model is for patients who still have their knee joint stable with all joint ligaments well in function.

If you consider to have this total knee model, discus this option carefully with your surgeon.

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Reference:

Rolston L et al.: Bicompartmental Knee Arthroplasty: A bone-sparing, ligament-sparing, and minimally invasive alternative for active patients. ORTHO Supersite; August 2007

Rolston L, et al: Bicompartmental knee arthroplasty: a bone-sparing, ligament-sparing, and minimally invasive alternative for active patients. Orthopedics. 2007 Aug;30(8 Suppl):70-3..

20/10/2007

PAIN INFLUENCES PATIENT SATISFACTION WITH TOTAL KNEE REPLACEMENT

You may think that it is a common sense: patient who continues to have pain in his / her total knee is dissatisfied with the operation result.

Yet, this is just the conclusion of a study published by British surgeons (Baker 2007). There is moreover a good reason why this study was conducted and published.

Most published results of total knee replacement present the percentage of failed total knees, the percentage of patients who needed revision operation of their total knee for whichever reason. So we will know from these studies how many total knees failed and needed a new operation. But we usually will not know how many patients with their total knees still in place were also satisfied with their total knee joint.

These studies present often “scores figure” which summarize in one numeral several items such as the range of motion in the knee joint and the activities of daily life that the patient can fulfill. But these figures did not tell anything about the patient’s satisfaction with his / her new joint.

The British surgeons sent a questionnaire to 10 000 patients who were operated on one year ago with total knee replacement asking about their satisfaction with the new total knee joint. Then they combined patient’s answer with data about the pain, range of motion, and function in the new knee.

The results are interesting and in some way chocking..

Actually only 82% of patients were satisfied more or less with their total knee performance one year after surgery. And only 8.6% of all patients reported “no or hardly any problems” with their new knee!

The unsatisfied patients have more often pain and less often bad function of their total knee as reason for dissatisfaction. Continuing severe pain troubled 20% of all patients, and pain on walking 17%!

But even satisfied patients had many complaints about their total knees, such as: difficult kneeling (57% of all patients), pain on starting of walk (78%), difficulties in washing and drying themselves (83%), and limp (80%).

Aged patients (>70 years) were more often satisfied than the younger patients (<65 years).

The authors also say that satisfaction was influenced by the choice of certain total knee models but give no details. Obviously this question is too delicate because it concerns individual manufacturers and may possibly influence their economical commitment to the future research.

A strange finding of this study is that “the grade of the lead surgeon” did not influence the satisfaction. Perhaps because even when the less experienced surgeon carried out the surgery, there was always a well experienced surgeon present to direct him, as is usual in hospitals educating new surgeons.

Information for you:

This study is very important. First, it shows the results of total knee replacement for a large patient group, not for a few carefully selected.

Second, It says that even if the operation result of your total knee surgery will be good (satisfying for you and excellent for your surgeon) expect a lot of smaller difficulties, such as occasional pain and limp. Especially if you are relatively young.

You should discuss very carefully the expected results of your total knee replacement with your surgeon and modify your expectations (if they are too great) with the view to the results presented in this study.

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Reference:

P. N. Baker et al.: The role of pain and function in determining patient satisfaction after total knee replacement. DATA FROM THE NATIONAL JOINT REGISTRY FOR ENGLAND AND WALES. Journal of Bone and Joint Surgery - British Volume, Vol 89-B, Issue 7, 893-900.

12/10/2007

E-VITAMIN , A PART OF YOUR TOTAL HIP IN THE FUTURE

This is a repost based on an advertisement. The August 2007 issue of The Journal of Bone and Joint Surgery contained a picture of a polyethylene cup made from polyethylene that was doped with vitamin E. The product is named E-poly and is produced by the Biomet Company.

The text says: "moving beyond simple wear reduction". The product has an interesting history. Although no patients have been operated on with this material as yet it demonstrates one thing: the cross-linked Polyethylene used in today's total hips has problems.

Picture of a cup component made from the E-poly TM HXLPE polyethylene

The industry discovered in the 1970’s how the chemical cross linking can improve the mechanical characteristics of the polyethylene. The modern industrial material used today for water tubing and electric isolation is chemically crosslinked polyethylene. There is, however, a trade-off for the cheap chemical cross-linking: the material contains the rests of chemical substances used for cross-linking.

Orthopedic surgeons introduced polyethylene cross-linked by radiation into the surgery of total joints in the 1990’s, because they needed a pure cross-linked polyethylene. The irradiated clean orthopaedic crosslinked polyethylene was, however, a fragile material.

This was an old knowledge. Already the well known 1973 textbook on materials and devices in surgery (Roaf & Williams) classified crosslinking of polyethylene by radiation as degradation process. They say that cross-linking by radiation makes the polyethylene fragile.

Such cross-linked polyethylene needs special heat treatment to make it less fragile. In spite of this treatment, the orthopaedic cross linked polyethylene, although pure polyethylene, is still a weak material, prone to fatigue fracture. See the previous report (04/10).

Already in 2004 the scientists and surgeons at the Department of Orthopaedic Surgery, Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, Boston, Massachusetts, USA conceived the hypothesis that addition of vitamin E to the polyethylene cross-linked by irradiation would make the material wear and fatigue fracture resistant. Such material would not need the special heat treatment, that deteriorated the mechanical characteristics of the polyethylene cross-linked by irradiation.

Subsequent laboratory tests confirmed this hypothesis (Oral 2006).

The ultimate strength, yield strength, elongation at break, and fatigue resistance of vitamin E-stabilized polyethylene (UHMWPE) were significantly higher than that of 100 kGy-irradiated and melted (UHMWPE), and were unaffected by accelerated aging. Rim impingement testing with 3.7-mm-thick acetabular liners up to 2 million-cycles showed no significant damage of the cross-linked liners made from UHMWPE doped with vitamin E compared with conventional, gamma-sterilized in inert UHMWPE. These are fine results- in laboratory.

See also the chapter: Bearing surfaces.

In May 2007 the Biomet Company and Dept of Orthopaedic Surgery at Massachusetts General Hospital, Boston, Massachusetts, USA, jointly announced that they will start a clinical experiment with the product. 400 patients will be recruited for operation with total hips, one group of patients will receive total hips with cups containing cups made from the E-poly.

Information for you: To my knowledge, this material is not yet available for general use. The history only demonstrates that the current crosslinked polyethylene used for total hip cups is not as good as some reports maintain. And although I have no individual wear data for the product, there are rumors that the E-poly cup articulating with metallic ball still wears more than ceramic on ceramic and metal on metal bearing combinations.

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References:

Oral E, et al.: Wear resistance and mechanical properties of highly cross-linked, ultrahigh-molecular weight polyethylene doped with vitamin E. J Arthroplasty. 2006; 21:580-91.

From: Department of Orthopaedic Surgery, Orthopaedic Biomechanics and Biomaterials Laboratory, Massachusetts General Hospital, Boston, Massachusetts, USA.

08/10/2007

IS IT SAFE TO TRAVEL EXTENSIVELY AFTER TOTAL HIP OPERATION? YES!

Long distance travel and total hip replacement are recognized as risk factors for development of Deep Vein Thrombosis (DVT).

As yet one does not know, however, how risky the long distance travel is for patients recently operated on with total hip replacement. Surgeons at the University of California, USA, thus studied 608 patients who traveled on average 1377 miles on average 6 days after total or resurface hip operation (Ball 2007).

All these patients have received prophylactic drugs against DVT. The majority of them traveled by airplane (462) or by car (143), only three traveled by train.

None of them suffered pulmonary embolism and only 0.8% suffered deep venous thromboses that needed treatment.

On the other hand, 1.5% of all patients suffered bleeding complication as side effect of prophylaxis against DVT.

Information for you: It seems to be relatively safe to conduct a long travel early on after the total of surface hip replacement. The major risk seems to bee bleeding because of prophylactic drugs that you will be taking against just DVT.

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References:

Ball ST et al.: Extended travel after hip arthroplasty surgery. Is it safe? J Arthroplasty. 2007 22(Suppl 2):29-32.

04/10/2007

CROSS-LINKED POLYETHYLENE CUPS – DAMAGE PREDICTED EARLIER REALIZES NOW

When Sir John Charnley introduced in the 1960’s the UHMWPE (Ultra-High Molecular Weight PolyEthylene) into the total hip surgery, he believed that he discovered an ideal material for cup components.

Since then the surgeons were tampering with the material to get rid of all its unfavorable characteristics. Under time the surgeons and material scientists tried to improve especially one bad characteristic of the UHMWPE: to diminish its propensity to wear off its surface in contact with metal and ceramic balls.

Under way, the material scientists tried different modifications of the UHMWPE to make it more wear resistant. They filled the UHMWPE with carbon fibers; they made it more crystal – like. The results were, however, a catastrophe. Lately, the material scientists discovered that in industry one uses a highly crosslinked UHMWPE.

Biomet's advertizement in 1991 of the Hylamer TM PE -

that failed later

So during the last five – ten years about every manufacturer developed its own cross - linked product. However, whereas the industry uses chemically cross-linked products, the orthopaedic device manufacturers are using polyethylene cross-linked by irradiation. The material scientists predicted repeatedly that this irradiated cross-linked polyethylene would have worse strength and fatigue endurance than the non-irradiated product. See also the chapter Polyethylene for total hips for details.

Click for the picture

The orthopaedic cross-linked polyethylene really wears 50 -90 % less than the non-irradiated non-cross-linked product.   There is, however, a trade-off for the decreased wear. The irradiated UHMWPE is weaker, it oxidizes, and it succumbs to fatigue failure easier than the non-irradiated product. As predicted.

The intact cup (left) and the cup with broken rim (right)

Recently, there appeared reports that cup components made from irradiated highly cross-linked UHMWPE broke on their rim (Currier 2007, Tower 2007). The deterioration of strength and fatigue endurance seems to occur in all trade marks of cross-linked orthopaedic polyethylene. The total hips with these failed cups need revision operation with exchange of the failed total hip device. A contributory cause to this failure was faulty position of the cup component in the studied cases.

The authors of these reports point out that “Half of the retrieved cups in this study exhibited fatigue damageon their rim (loss of material through delamination and/or cracking).This fatigue damage after a short time in vivo (as little asthree years in all but one case) raises concerns about debrisgeneration by material removal through delamination and thepotential for more serious cracking leading to rim separation” (Currier 2007).

A rather serious warning, published in a leading orthopaedic journal. How will the manufacturers react?

Information for you: Almost all manufacturers of total hips use today highly cross-linked polyethylene in their products. So you have no choice to have a “non cross-linked” total hip operated on. The “concern” about which the authors speak is related mainly to total hips with faulty position of the cup components.

Because it is known that surgeons with great experience place their total hips more often in right position than their colleagues who operate on more sparsely, your chance is to find an experienced surgeon for your operation with the cup made from a highly cross-linked UHMWPE. Or contemplate about another material for your total hip than just the highly cross-linked polyethylene.

Biomet just (May 2007) announced polyethylene doped with E-vitamin (E-poly). Will it be a solution to Sir John Charnley’s unlucky heritage?

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References:

Barbara H. Currier, MChE et al: Evaluation of Oxidation and Fatigue Damage of Retrieved Crossfire Polyethylene Acetabular Cups. The Journal of Bone and Joint Surgery (American). 2007;89-A:2023-2029..

Stephen S. Tower, MD et al: Rim Cracking of the Cross-Linked Longevity Polyethylene Acetabular Liner After Total Hip Arthroplasty The Journal of Bone and Joint Surgery (American). 2007;89-A:2212-2217

References:

Pulido L. et al: In hospital complications after total joint arthroplasty. J Arthroplasty. 2008 Sep;23 (Suppl 1):139-45.

01/10/2008

HIGH-DEMAND SPORTS AFTER TOTAL KNEE REPLACEMENT

Information for you: You should consider this report rather than curiosity that recommendation. The follow up applies to only a very small patient group and there is no control group for comparison.

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Reference:

Mont MA, et al: High-impact sports after total knee arthroplasty. J Arthroplasty. 2008 23(6 Suppl 1):80-4

Reference: : Bolognesi MP et al.: The impact of diabetes on perioperative patient outcomes after total hip and total knee arthroplasty in the United States. J Arthroplasty. 2008; 23(6 Suppl 1):92-8.

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.

Reference: Koskinen E. et al: Comparison of survival and cost-effectiveness between unicondylar arthroplasty and total knee arthroplasty…… Acta Orthopaedica 2008; 79: 499 - 507

Reference:

McBryde CW et al : The Influence of Surgical Approach on Outcome in Birmingham Hip Resurfacing. Clin Orthop Relat Res. 2008 [Epub ahead of print]

Reference:

Toms AP et al: MRI of early symptomatic metal-on-metal total hip arthroplasty: a retrospective review of radiological findings in 20 hips. Clin Radiol. 2008 Jan;63(1):49-58. Epub 2007 Oct 24.

Reference:

Colwell CW Jr, et al.: Ceramic-on-Ceramic Total Hip Arthroplasty Early Dislocation Rate. Clin Orthop Relat Res. 2007 Jul 19;Publish Ahead of Print [Epub ahead of print]

Reference:

Restrepo C. et al. The noisy ceramic hip: is component malpositioning the cause? J Arthroplasty. 2008 Aug;23(5):643-9

Reference:

Reference:

Wylde V et al: Return to sport after joint replacement. J Bone Joint Surgery-Br 2008: 90-B: 920-3

Reference:

William G. Rodkey et al: Comparison of the Collagen Meniscus Implant with Partial Meniscectomy. A Prospective Randomized Trial. J Bone Joint Surg Am. 2008;90-A:1413-1426.

Reference:

Rapp S.M.: ORTHOPEDICS TODAY 2008; 28:70

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T. C. B. Pollard, et al.: The assessment of early osteoarthritis. Journal of Bone and Joint Surgery - British Volume,2008, Vol 90-B, 411-421

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Lidgren L.: Chronic inflammation, joint replacement and malignant lymphoma. Journal of Bone and Joint Surgery - British Volume; Vol 90-B: 7-10.

Andrew Quoc Dutton et al: Computer-Assisted Minimally Invasive Total Knee Arthroplasty Compared with Standard Total Knee Arthroplasty. A Prospective, Randomized Study . The Journal of Bone and Joint Surgery (American). 2008;90-A:2-9.

P. N. Baker et al.: The role of pain and function in determining patient satisfaction after total knee replacement. DATA FROM THE NATIONAL JOINT REGISTRY FOR ENGLAND AND WALES. Journal of Bone and Joint Surgery - British Volume, Vol 89-B, Issue 7, 893-900.

Barbara H. Currier, MChE et al: Evaluation of Oxidation and Fatigue Damage of Retrieved Crossfire Polyethylene Acetabular Cups. The Journal of Bone and Joint Surgery (American). 2007;89-A:2023-2029..