NEWS

18/07/2010

PESSIMISTIC PATIENTS HAVE MORE PAIN AND WORSE FUNCTION IN THEIR TOTAL KNEES.

Experienced surgeons have since long known that distressed, anxious patients were more difficult to attain freedom from pain with total joint operation. A new study from a prominent American university (Mayo Clinic, Rochester, Minn) demonstrated that also patients with pessimistic psychological characteristics had more pain and less function up to 2 year after total knee surgery, compared with “normal” patients (Singh 2010).

However, this difference in results disappeared with a new control 5 years after surgery. Then had both pessimistic and optimistic patients had equally good results.

Information for you;

By an optimist may not be easy, I now it! But it is rewarding. In this paper the authors discuss the possibility to “screen the patients for their place on the optimistic – pessimistic scale” already before the surgery. It is done by a huge psychological test. The patients with such stressors such as depression and anxiety can then have “cognitive –behavioral interventions specifically set for patients with total joint replacement. Such interventions are under development.

As for now, if the psychological examination revealed that you are a pessimist, the surgeon can discuss the postoperative expectation in more realistic terms.

References;

Singh J.A. et al: Pessimistic explanatory style. J Bone Joint Surg-B 2010; 92-B: 799 - 806

30/06/2010

Venous Thromboembolic Disease – once more

I got questions about the prophylaxis against DVT (Deep Vein Thrombosis. The people were interested to know why the “official” recommendations of prophylactic measures could produce so serious side effects as my January report showed (Prophylaxis against DVT - when the authorities recommend).

Two recently published articles in the British Journal of Bone and Joint Surgery reveal “the error of process that caused problems with the initial guidance” (Atkins 2010, Treasure et al. 2010) . I tried here to summarise these articles to you.

VTE (venous thromboembolisms) and prevention against it involves both doctors and industry (drugs, kinetic devices, stockings). General aggressive prophylactic measures against VTE with modern drugs (low molecular heparin) applied to all patients operated on with total joint replacement are costly on the one hand, and render money to the pharmaceutical industry on the other. Moreover, because the number of total joint replacements will growth in the future years, the industry is interested to keep this aggressive/costly prophylaxis going.

From this point of view one can understand that much of the present debate has been about who should give the instructions to orthopaedic surgeons about prophylaxis against VTE, orthopaedic surgeons or specialists on blood and blood diseases(haematologists).

During this debate, much accusation was made of “undeclared intellectual conflicts of interest”. In my translation this should read “getting grants from pharmaceutical industry for presenting desired results”.

The haematologists accused in the debate orthopaedic surgeons that “their recommendations are based on expert opinion and lacks scientific basis”. Meaning that the surgeons who saw in their everyday practice bleeding caused in their patients by “aggressive prophylaxis” were “overstated their concern”. They were “biased”.

To make prophylaxis against VTE big issue that justifies the money spent on prevention, it was necessary to demonstrate that VTE is really a frequently occurring complication leading often to the fatal pulmonary emboli.

The British House of Commons Health Committee published in 2005 a report in which they stated that deaths from Pulmonary Embolism have more victims than “AIDS and cancer together” with 25 000 patients dying annually from this complication. In the report there was no reference how the politicians arrived at this huge figure.

Later investigation revealed that the high figure “is an estimate derived from…modelling exercises”, The Office of National Statistics recorded only 3047 deaths from PE for the year 2008. Obviously, “modelling exercises” used instead of original data produce unpredictable results.

The British National Institute for Health and Clinical Excellence (NICE), however, published in 2007 guidance to the orthopaedic surgeons how to prevent VTE after total hip and knee surgery. This guidance recommends general and aggressive prevention of DVT.

If this publication was related to the House of Common document I do not know (personally I would answer “Yes”)

The guidance was based on several wrong assumptions (for example that the incidence of thrombus in the calf veins is directly proportional to the incidence of the deadly PE. Pharmacological companies use this technique (frequency of thrombi in calf veins) in studying the effect of new antithrombotic drugs. The majority of these calf thrombi cause no symptoms to the patient and disappear silently without any consequences).

It later appeared that NICE (a government institution) did not invite practicing orthopaedic surgeons on the panel that produced the 2007 Guidance. Reason: “undeclared intellectual conflicts of interest” in orthopaedic surgeons. Instead, the haematologists and “methodologists” produced the recommendations. The British document followed in much the recommendations published previously by the American College of Chest Physicians that recommended massive use of modern antithrombotic drugs (low-molecular weight heparin).

The recommendations in this document were followed by more than two third of British orthopaedic surgeons with the consequence I described in my January report (here). This “raised concern” of British surgeons, which successively led NICE to establish a new panel of specialists with many practicing orthopaedic surgeons included. This is nicely described in the Treasure’s et al article.

This new panel then published new guidance for prevention of thromboembolic events (January 2010).

http://www.nice.org.uk/nicemedia/live/12695/47197/47197.pdf

These new guidance recommends serial risk assessment of every individual patients as long as risk analysis justifies it. It respects the individual patient’s needs, wishes, and compliance. Only selected patients need aggressive prophylaxis against VTE complications.

One thing is sure: implementing the new NICE guidance (2010) will be time consuming and costly.

In the USA the development took similar path. The official organization of American surgeons, the AAOS (American Academy of Orthopaedic Surgeons) collaborated with Agency for Healthcare Research and Quality. They found after literary studies that prophylaxis against VTE according to the guidance developed by the American College of Chest Physicians was most effective. Thus, AAOS recommended this guidance also for patients operated on with artificial joints in 2004 (Haas 2008).

Here again, the aggressive treatment with modern anticoagulant drugs (heparin derivates) was recommended. The American orthopaedic surgeons soon were concerned when the data on the bleeding complications associated with this type of prophylaxis became published.

Again, it became apparent that the opinion of orthopaedic surgeons, who were concerned of bleedings caused by aggressive use of anticoagulant drugs strongly differed from the opinion of haematologists who were concerned for the VTE.

The debate widened to the question who was entitled to give guidance to practicing orthopaedic surgeons. The orthopaedic surgeons rightly pointed to the fact that “the independent methodologists” were not independent. These people were devoted to study the blood clotting, so in the debate they were called “thrombologists”. Very often, these thrombologists were receiving grants from pharmacological companies for their studies, with all possible dependences.

As a result of this debate, The American Academy created its own guidance committee on VTE prophylaxis in 2006 consisting mainly of practicing orthopaedic surgeons. This committee produced the guidance on prophylaxis against VTE in total joint replacement surgery one year later:

http://www.aaos.org/Research/guidelines/PE_guideline.pdf

It takes similar care of individual patient’s needs and wishes as the British document.

Information for you:

When you are awaiting total joint surgery, discuss carefully the prevention against VTE. It is possible that you not will need any drug prophylaxis, that you will have sufficient prophylaxis with only

mechanical devices. The British guidance has excellent patient information.

References;

Atkins RM: NICE and venous thromboembolism. J Bone Joint Surg – B 2010; 92-B: 609 - 10

Treasure T. et al.: Developing guidelines for venous thrombolism for The National Institute for Clinical Excellence. J Bone Joint Surg – B 2010; 92-B: 611 - 16

Haas S.B. et al: Venous thromboembolic disease after total hip and knee surgery. J Bone Joint Surg- Am, 9o-A: 2764 - 80

20/04/2010

MINIMAL INCISION TOTAL HIP SURGERY – A RISK FACTOR RATHER THAN LASTING SUCCESS?

The minimal incision surgery (MIS) technique for total hip replacement increased in popularity although there were no reliable reports of whether this operation technique produces equally lasting results as the conventional surgical techniques.

A more sober reports are now appearing indicating the risks of the MIS technique.

A group of American surgeons investigated revision surgeries in two patient groups, one operated on with MIS technique, the other one operated on with traditional techniques (Graw 2010). They discovered that patients operated on with MIS technique required revision early after operation, within 2 years. On the other hand the patients operated on with conventional techniques required revision operation much later (mean period to revision operation 14 years).

The main causes for early revision operations after MIS surgery were undiscovered fractures during surgery and bad placement of the total hip components.

In another report, Dutch surgeons followed up two patients groups, both operated on with total hip replacement (Goosen 2010). The one group was operated on with MIS technique, the other group was operated on with conventional technique with large (18 cm long) incision.

It appeared that within one year, the functional recovery of patients in both groups was equally speedy and both groups attained equally good functional capacity in their operated on hip joints. The group of MIS patients, however, had much longer operation time, the surgeons using MIS technique had made more faults initially (had longer “learning curve”) and the patients suffered more complications during the surgery that needed early early return to the operation room.

In the third report, published by the American surgeons, the surgeons followed the fate of patients who suffered a complication during total hip surgery that required return to the operation room (fractures discovered after the end of surgery, instability, bad position of the components, nerve damage) (Darwiche 2010). It appeared that 33% of these patients suffered later on deep infection of their total hip. The majority of patients that need early return to the operation room were operated on with MIS technique, as shown in other reports.

Information for you: These reports are not statistically foolproof, but still arise suspicion that MIS may make the total hip replacement more difficult for the surgeon and result in unnecessary trauma of patients tissues. On the other hand, you have not so much to win if you are operated on with the shorter incision approach to the hip joint.

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References:

Graw BP et al.: Minimal Incision Surgery as a risk factor for early failure of total hip arthroplasty. Clin Orthop Relat Res 2010 Mar 30 (E publ ahead of print)

Goosen JH et al.: Minimally invasive versus classic Procedure…… Clin Orthop Relat Res 2010, Mar 30 (E-publ ahead of print)

Darwiche H et al.: Retrospective Analysis of infection rate after early reoperation in total hip arthroplasty. Clin Orthop Relat Res 2010, Mar 30 ((E publ ahead of print)

10/04/2010

DVT (DEEP VEIN PROPHYLAXIS) IN TOTAL JOINT SURGERY? YES, BUT WHICH ONE?

Surgeons recognize that total joint surgery carries a risk of DVT.

Preventive measures to prevent formation of venous thrombus are recommended for two reasons:

First: Deep vein thrombus may produce Pulmonary Embolism (PE). Whereas deep vein thrombus itself usually does not pose any problems for the patient or the surgeon, when the blood clot travels upstream it may produce PE with possibly lethal outcome.

Second: Production of medicines to prevent DVT generates big incomes to pharmaceutical industry.

Thus, it is not surprising that there are several clinical guidelines how to prevent DVT after total joint surgery. (See the chapter Deep Vein Thrombosis). Because almost all research of DVT is financed by pharmaceutical industry the recommendations of prophylaxis suit more to the pharmaceutical industry needs than the orthopaedic patients. One such example is the fact that the efficacy of prophylactic medicines in published studies has been assessed by reduction of DVT seen on the venogram (x-ray pictures of vein system). The clots in lower legs veins are relatively frequent after total hip and total knee surgery and usually pose no problems for the patients. But from the statistical point of view it is easy to demonstrate their reduction by a medicine. Thus, a steady stream of new, and more effective (“aggressive”) drugs with effect on creation of blood clots are developed and introduced on the market.

The clinically important PE, on the contrary, is a rare event (about 0,5 – 2%). Thus to demonstrate a statistically significant preventive effect of a drug on this condition a large number of patients is needed and consequently such study would be costly for the pharmaceutical company. Thus, such studies are rare.

On the other hand, the “aggressive” new drugs that more effectively prevent production of blood clots carry also increasing risk of bleeding in patients with total joint surgery. This side of the chemical prevention of DVT has not been studied sufficiently in clinical studies of the new prophylactic drugs. As I said, the main attention in these studies was concentrated on diminishing (prevention) of blood clots in the deep veins of the legs, whereas the postoperative bleeding was considered as rather a “nuisance”. For surgeons and their total joint patients the postoperative bleeding is, however, a very serious problem. The frequency of this complication increased when new, more “aggressive” prophylactic drugs were introduced in the surgery of total joints.

The problem will be apparent from the study by Haas and his colleagues (2008). They studied the published literature on the different prophylactic regimes after total hip and knee arthroplasty and their study showed following data for the total hip patients.

On the one side of the balance scale is the efficacy of prophylactic drugs. After chemical prophylaxis with Warfarin, low molecular weight heparin, and Fondaprinux 0.4 % of all operated on patients developed signs of pulmonary embolism. Totally 0.05% patients died of this complication.

On the other side of the balance scale are the major bleeding complications that follow with this prophylactic treatment. Thus, 2.5 % of all operated on patients developed major bleeding and 0.06% of them died from this complication. Obviously, the rate of side effects of pharmaceutical DVT prophylaxis is unacceptably high. Especially when one considers the fact that patients with only mechanical prophylaxis (foot and leg pumps) had 0.7 % of pulmonary embolism complications with 0.09 % deaths, but no bleeding complications.

One must consider that patients with mechanic prophylaxis had very probably a low risk of pulmonary embolism (otherwise the surgeon would assign them to chemical prophylaxis). That is the point of the whole study: Chemical prophylaxis is dangerous and only carefully selected patients should have it.

Information for you:

Modern drugs for prophylaxis against deep vein thrombosis are really dangerous when applied generally without proper patient selection. Discuss always with your surgeon the type of prophylaxis against DVT that is most suitable in your case. In young, healthy patients with no risk factors no chemical prophylaxis may carry the lowest risk of pulmonary embolism,

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References:

Guidelines help clinicians identify safe DVT prophylaxis strategies. ORTHO Super Site, March 2010; 30:1

Haase S. et al. : Venous thromboembolic Disease after total hip and total knee arthroplasty. J Bone Jt Surg – Am 2008; 90-A: 2764 -

24/03/2010

METAL ON METAL: IS IT WORTH THE RISK?

Two eminent American surgeons and one material scientist present the advantages and risks of the modern metal on metal artificial hips (Crawford 2010). Their conclusion: “There has been no conclusive proof supporting the use of metal on metal bearings”.

There has been an explosion in the use of metal on metal bearings (MOM) in the last years throughout the world.

This has been mostly driven by the increase of surface hip replacements that uses metal bearings, but also the use of total hip prostheses with mega (large) metal heads increased during the last five years.

The alleged advantage of MOM bearings is the possibility to use femoral ball components that come close to the size of the natural femoral head (> 50 mm diameter). Such large femoral balls have low risk of dislocation as documented in the National Hip Joint Registries.

On the other hand, another alleged advantage of large diameter femoral heads, the low wear rate, was never documented convincingly.

It is true that the total volume of wear particles in MOM total hips is lower than the volume of polyethylene particles in the metal on polyethylene total hips. Because the metallic particles are much smaller than polyethylene particles, however, the total number of metallic particles produced by MOM total hips is much greater than the number of polyethylene particles. And it is the number of wear particles that counts.

Accordingly, National Hip Joint Registries (England, Australia) show higher rates of failures of MOM total and surface hip replacements compared with metal on polyethylene total hips.

Together with the increased use of MOM hip replacements there was worrying increase in complications: osteolysis (bone dissolving disease), local soft tissue tumors (specific allergic? reaction to metallic components), and death of bone tissue around the MOM prostheses.

Revision operations after failed surface replacements are not easy as alleged in advertising campaigns. On the contrary, they fail very often, and a third operation is then necessary.

Information for you: The opinion of these three authors may seem to by a little biased, but nevertheless they have good support in the published statistics.

Probably a cautious approach would be on place: if you need an extra large femoral head component, or if you will have a surface replacement with a large component, then it may be worth to accept the risk, otherwise other bearing surfaces would be preferable.

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References:

Crawford R, Ranawat Ch, Rothman RH.: Metal on Metal: Is it worth the risk?, J Arthroplasty 2010, 25: 1-2

18/03/2010

IMPACT SPORTS DO NOT MATTER FOR TOTAL KNEES SURVIVAL?

If you ask your surgeon about sports activity after your total knee replacement he/she would very probably inform you that doing sports is beneficial but doing high-impact sport is not recommended. See also the chapter Sports and total knee. But your surgeon would have difficulty to find direct proof of the harmful influence of impact sports on the survival of implanted total knees.

Recently an American surgeon produced even a statistics demonstrating that patients who do high impact sports have equal survival chances as patients who do low impact sports or who do no sports at all (Parratte 2010).

He evaluated survival of 218 total knees in patients who claimed participating in high impact sports seven years after surgery and compared it with a group of 370 total knee operated patients participating in low-impact sports or in no sport activity at all. The patient mix (gender, age, activity) and prosthesis model were similar in both groups.

It appeared that the survival rate of the total knees after seven years was equal in both groups.

Information for you:

Can this (as yet unique) statistics be a basis for recommendation of high impact sports to TK patients? Certainly not. This a typical meeting report with weak arguments. For one, the patients with high impact sports listed tennis (single or double?), golf!, and swimming. The two last sports are not even classified as high impact.

For the other, the author selected his patients in an unclear way from a large amount (1200) patients operated on. It is possible that this unplanned selection skewed (biased) the whole study.

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References:

Parratte L.: Similar survivorship of total knee in patients performing high and low-impact sports. Presented at the 2010 Annual Meeting of AAOS, March 2010 10-13, New Orleans.

14/03/2010

INFECTION WITH RESISTANT STAPHYLOCOCCI NOT SO DELETERIOUS AS RUMORED

There is one strain of staphylococci resistant to synthetic penicillin (MRSA) that causes severe infection of total joints difficult to treat. Orthopaedic surgeons always fear these infections in total hip and knee replacement as they often leave severely mutilated joints.

Now a group of American surgeons presented results that demonstrate that with proper treatment the MRSA infections of total knees leave motion and outcomes similar to those attained by patients treated for infections of total knees caused by other bacteria (McGough 2010)

The surgeons studied the functional outcome of 49 total knees revision operated. From the operation and two years after that.

It appeared that 2 years postoperatively, these patients had equally good function in their knees and equally good pain relief. Noticeable was, however, that total knees with MRSA had significantly longer (20%) operation time for the revision than total knees revised for infection caused by other bacteria.

Information for you: the good news is that MRSA can be treated so effectively. The longer operation time for these patients, however, means that these infection cause really severe destruction of the skeleton around the infected total knee.

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References:

McGough et al.:MRSA septic TKA revisions yield typical post-revision outcomes. Presented at the 2010 Annual Meeting of the AAOS, March 9 -13, New Orleans.

04/03/2010

ORTHOPAEDIC SURGEONS AND THE ORTHOPAEDIC DEVICES INDUSTRY. HOW BIG A KICKBACK?

When a patient visits a doctor, he or she shares sensitive information with the doctor, relies on the advices provided, and comply with treatment recommended. In exchange the patient expects undivided loyalty from his/her physician.

This loyalty is betrayed if the doctors have financial self-interest in the medicines he recommends or if the surgeons have financial self-interest in the orthopaedic total joints they use in operation on their patients.

Recently USA’s orthopaedic surgeons published a summary of the examination of the “Big-Five” Companies producing 95 % of all total knee and hip prostheses in the USA (Gelberman 2010). The Dept of Justice’s examination demonstrated that all Big-Five Companies violated the Federal Anti-Kickback Statute.

Examination demonstrated that industry funding of orthopaedic research and payment of kickback to individual surgeon influenced the results of several studies of total joints. Favorable results (results favorable for the company’s product) were published, negative results were suppressed. This is obvious from the following statistics:

Results of total hip surgery were favorable for the model manufactured by the sponsor in 93% of published studies, whereas in statistics published by an independent surgeon the results were favorable for identical model only in 37 % of reports. Similarly, for total knee models the published results were favorable in 75 % of all sponsored reports and only in 20 % of reports published by independent surgeons.

Information for you: These data show that today’s science of total joints is tainted, even if many surgeons who received special reimbursement and consultant fees would not agree. Please, do not misunderstand: these surgeons, paid by the Companies, however, do not lie, they do not commit fraud when publishing favorable results. These surgeons tell the truth and the truth only, but not the whole truth. The inconvenient results are simply not published.

In this article the authors say that the guilt of suppressing inconvenient results lies not only with the Companies, but also with the surgeons.

Second, it would be wrong to suspect that every inventor-surgeon conceal his/her bad results and does not take action when such bad results appear. It is rather so that the “ordinary” surgeons may continue to use wrong methods and models because of financial incentives from the manufacturer/ hospital/ care provider.

This implies that you most look on “the conflict of interest” statement in every published report. If the authors acknowledge substantial payment from the manufacturer then you should be more critical when reading the results.

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References:

Gelberman RH et al.: Orthopaedic Surgeons and The Medical Device Industry. J Bone Joint Surg-Am, 2010; 92-A: 765 -777

23/02/2010

POROUS COATING IMPROVES FIXATION OF TOTAL KNEE

Cementless total knee relies on ingrowth of bone tissue in its outer surface for its fixation to the bone (See the chapter Outline total knee prosthesis / cemented & cementless.

Unfortunately, the tibial component of the total knee prosthesis is made of a metal plate which bears a polyethylene inlay. The stiff metallic back up plate, (made often from cobalt-chrome alloys, and protects the bone from taking loads, so that the bone tissues atrophy.

The solution would be to use a more elastic metal than cobalt-chrome alloy.

The solution would be to use a more elastic metal than cobalt-chrome alloy. Scientists at Zimmer developed porous tantalum metal (trabecular metal) which has elasticity more like the bone tissue.

On this picture you see the outer (lower) surface of the tibial component which is made of trabecular metal.

41 patients who had a total knee prosthesis that uses this trabecular metal for the tibial component (NexGen TM, Zimmer) implanted were studied. The surgeons wished to know whether this total knee prosthesis really prevented atrophy of the bone tissue around the tibial component.

The patients had x-ray pictures of their total knee and the skeleton around it done after 1, 6, and 24 months after surgery. It appeared that the trabeculous metal in the tibial component maintained the bone mineral density of the operated on knee up to 2 years after surgery. This observation proves that the trabecular metal not only in teory but also in practice does not prevent transfer of body weight on the bone tissue directly underneath under the total knee prosthesis.

Information for you: Very interesting and hopeful observation. You should, however, keep in mind that 1) the observation period is very short, and 2) that the report does not tell about possible other complications..

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References:

Harrison AC et al.: Do porous implants help preserve bone? Clin Orthop Relat Res Published online 12. January 2010

19/02/2010

METAL ON METAL TOTAL HIPS FAIL BECAUSE OF METAL ALLERGY

The body reacts to the metals contained in the Cobalt-Chrome alloy that is used for manufacturing of total hip joints. Greek surgeons published recently very nice pictures that confirm this hypothesis (Aroukatos 2009).

They compared the microscopic pictures done on the capsules from two groups of failed total hips. One patient group was operated on with ceramic on polyethylene total hips, the other group was operated on with metal on metal total hips. The metal used for manufacture of the metal on metal total hips was Sicomet, a low carbide Cobalt Chrome alloy.

The capsules of the failed metal on metal total hips showed signs of immunologic hypersensitivity to metals whereas such signs were absent in patients operated on with ceramic on polyethylene total hips.

Low carbide Chrome - Cobalt alloys are known to have high wear rates of small metallic particles, which lead to overburdening of soft tissues around the hip prosthesis with metal and causes local allergic reaction there. The allergic reaction eventually causes destruction of the bone to which the total prosthesis once was anchored. The prosthesis is then loose.

This mechanism of failure was recently proven for the surface replacement hips, now the Greek surgeons showed that it appears also in total hips if wrong metal material is used for their manufacture .

Information to you:

Once one example of failed armchair philosophy: “a new, better material” may actually be worse. This is so because the Sikomet TM (Smith & Nephew new Co –Cr alloy) was made low carbon to improve the alloy’s structure, diminish its porosity. The improvement made, however, the Sicomet too soft with increased wear rates as a consequence.

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References:

Aroukatos P et al.: Immunologic adverse reaction associated with low-carbide metal-on-metal bearings. Clin Orthop Relat Res, published online 18.Decemeber 2009

5/02/2010

HIGH FAILURE RATE OF UNCEMENTED CUP COMPONENTS – OF MODELS NO LONGER IN USE

Norway’s National hip register has excellent database on practically all total hip replacement operations carried out in Norway since 1987. The scientists and surgeons at the Nationla hip register studied one disquieting fact that appeared in several reports worldwide: the high failure rates of metal backed cup components (Hallan 2010).

During the period from 1987 through to 2007, 66 different models of uncemented acetabular cups were used by Norwegian surgeons in 19 255 operations. From this tremendous amount of models the authors choose 8 models that have had cup polyethylene inlay made from the conventional Ultra High Molecular weight polyethylene and were used in at least 400 operations.

Already these figures show the problems with the statistics of the results of total hip replacement in a world where there appear a stream of new total hip models every year (and about as many silently disappear). Se also the chapter on Cemented and cementless total hips

The authors found that in the short term the results of these eight cup models were good –less than 4 % failures during the first seven postoperative years. But the after seven years the failures began to increase dramatically,, with up to 19 % of cups failed at the end of twelve years after surgery. These late failures were mainly failures of the polyethylene cup component; with increased wear and destruction of the polyethylene component, and eventually loosening of the whole device.

Information for you: This report reveals that the “old” UHMW polyethylene, really suffers fatigue failure - it begins to fall to pieces after seven years of flawless function. This kind of UHMW polyethylene is yet another bad heritage from the early constructions of total hip devices.

The authors say that the new cross-linked (XLPE) polyethylene will not suffer the fatigue failure so that the problem will be lost. Unfortunately, there are as yet no statistics about the long-term performance of the cup components made from XLPE to be sure. In every case, the most failure prone total hip models pinpointed in this report are no longer used in Norway.

This statistics is also a reason to look seriously on other alternatives of bearing surface combinations (metal-on-metal and ceramic-on-ceramic).

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References

Hallan G. et al: Metal.backed acetabular components with conventional polyethylene. J Bone Jt Surg-Br 2010; 92-B: 196 - 201

12/02/2010

CATASTROPHIC FAILURES OF BIRMINGHAM SURFACE HIP – A HISTORY WITH HAPPY END

McMinn developed his surface replacement hip device in 1991; the device was manufactured by Corin Ltd, an English company. It is known that McMinn changed the manufacturer (and device’s design) after 1996, but it was not known why.

In a recently published article a group of scientists and surgeons around Doctor McMinn describe why the “1996 device model “ was changed (Daniel 2010).

In the article the authors tell a curious history. In the years 1994 and 1995 Birmingham surgeons carried out 107 operations of surface replacement (on 99 patients) with the McMinn hybrid resurfacing device, manufactured by Corn Ltd Company. This prosthesis was manufactured from Cobalt-Chrome alloy with high carbon content.

In 1996 year a new version of the cup component of this device was introduced. This version was produced according a new manufacturing process (double heat treatment) that should diminish the great porosity of the bearing surfaces. Theoretically, reducing the porosity of the bearing surfaces of the device was advantageous (it diminished wear), so the manufacturer decided to give the device not one but two heat treatments, following the rule “if one treatment makes got, two treatments would do better”.

This was an important change in the manufacturing process but the manufacturer “forgot” to inform the surgeons and designers of the device. Totally 184 operations (on 181 patients) were carried out with this “1996” device during the 1996 year. Now a curious thing appeared: 12 patients operated on with this version of device reported screeching and clicking noises from the operated on hips. The surgeons took the clever decision to investigate the reason for the noises and stopped the use of the device at the end of the 1996 year.

All patients operated on with the “1996” version of the device were followed out and nothing special happened; the sounds from the replaced hips successively disappeared and at the 5 year follow up the failure rates for the “1996” surface hips were under the benchmark, about equally small as the failure rates of patients operated on with the device in the 1994 and 1995 years.

The ten year control showed, however, that the “1996” double heat treated version of the McMinn model was producing catastrophic rates of failures:

Totally 16 percent of replacement operations failed during the ten years period after surgery in this group, compared with only 7 % of failed operations in the patients operated on with the “old” (1994 & 1995) version of the device.

This picture shows the cumulative percentage of failures in both patients groups: the red curve shows the failures for the “1996” group, the blue curve shows the failures for the 1994 & 1995 year operation group.

Note that up to the five years postoperatively, the failure rates are equal for both groups. (arrow)

Ironically enough, all 12 patients with “the noisy surface hips”, who were the primary reason why the “1996 device” was withdrawn, survived the ten year postoperative period without failure!

Information for you: Five year results of the surface replacement surgery are unreliable. Unfortunately, most published statistics about this type of replacement are based on just five years of observation. In this history another curious thing happened: the use of a surface replacement device was stopped because of “wrong” reason: sounds produced by the device. The noises were not a sign of imminent failure. But should the surgeons not care about patients’ claims and continue with the use of the “1996” version of the device, the number of failures would really take catastrophic proportions.

And again, an armchair was working here: The heat treatment (and isostatic pressing) diminished the porosity of the metallic bearing surfaces and diminished the wear when done only once. But heat treatment done twice made the surfaces soft and increased the metallic wear instead. High metallic wear with deposition of metallic particles in the tissues around the device leads to known consequences: severe damage of the tissues round the device and eventually loosening of the device. These changes were found in 29 out of 30 failed surface hips in the “1996” group.

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References

Daniel J et al: Ten year results of a double heat-treated metal on metal hip resurfacing. J Bone Joint Surg-Br 2010; 92-B, 20 – 27.

20/01/2010

RISK TO DIE AFTER HIP AND KNEE REPLACEMENT SURGERY – IT EXISTS BUT IT IS VERY SMALL

Many studies demonstrated that patients operated on with total hip or total knee replacement are living longer than their fellows from the general population. One considers that this lower mortality is the effect of the selection of relatively healthy patients for these operations.

Does this effect also apply to the time period immediately after surgery? With immediately one means the first 10 to 20 days after surgery. For statistical study of this question one needs to study large patient populations.

Norwegian and Australian surgeons pooled their National Joint Registries together, totally 187 000 patients (Lie 2010).

It appeared that the mortality immediately after surgery was increased but steadily decreased until it sank to the “baseline level” (BL) on the 26 day after surgery.

Two groups of patients showed in general increased early postoperative mortality: men and patients >70 years old.

Information for you: This huge statistics demonstrated that “excess” mortality after total hip and knee surgery is still very low – 0.12% patients died during the first 26 days. The increase of excessive mortality was highest immediately after surgery. The authors demonstrated in their previous reports that these earliest deaths were mostly attributable to lung emboli and other vascular accidents. Thus, there is no reason why the fear for the postoperative death should deter you from the planned total joint surgery.

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References:

Lie SA et al: Duration of the increase…J Bone Joint Surg-Am 2010; 92-A: 58 - 63

2/01/2010

AN EXPENSIVE INNOVATION THAT IS NOT WORTH MONEY? CASE OF HYDROXYAPATITE COATING.

Please, read also the chapter Cemented and cementless total hips / Hydroxyapatite.

In the 1980’s the surgeons who began to insert cementless total hip joints pondered about the means how to speed the ingrowth of bone tissue in the porous surface of the total hip devices. Soon there were published reports demonstrating that hydroxyapatite was a substance that, when attached to the surface of the device, will enhance early ingrowth of the bone tissue into the porous surface of the total hip. Early ingrowth will then secure aeternal stability of such HA coated total hip model.

Manufacturers recognized quickly that HA coating may be an advantage in promoting the total hip device on the market and to improve the company's revenues. Since the 1980's the manufacturers are producing a "vast array" of total hip models with surfaces coated with HA

An advert admonished the surgeon to stay on the top with a HA coated total hip (JRI, Furlong), another advert proclaimed that all HA are NOT created equal (Howmedica, LPPS HA), promoting manufacturers own HA product.

Quickly also appeared reports on small group of patients operated on with HA coated total hips; the observation periods in these reports were short and the results were excellent.

Soon, however, surgeons discovered also disadvantages of HA coatings: The HA crystals’ fixation to the surface of the total joint was not 100%; some of these (relatively hard) crystals tumbled from the surface and wandered inside the artificial joint, scratching the joint surfaces there.. Increased wear ensued, with precocious loosening and osteolysis. In yet other patients the thin HA surface was simply resorbed by soft tissues leaving empty space between the bone and the surface of he total hip. Instead of stability followed loose state of such implanted total hip.

Were these complications frequent? Was HA coating even a risk factor for failure of the total hip?

A group of Swedish surgeon used data registered in the Swedish National Hip register to answer this question (Lazarinis 2010). They studied 8 043 total hip operations done with three total hip models (Romanus, Trilogy, Harris-Galante).

In 5 213 operations the surgeon used a JA coated cup, in 2 830 operations the surgeon used identical cup model but without HA.

It appeared that HA coating increased the risk of failure by loosening 1.8 times in general and for two models (Romanus, Harris-Galante) the risk increased 2.5 times if the cup was HA coated. It should be noted that the HA coating of these three cup models contained only 70 % of synthetic bone mineral (HA) and rest was a simple chemical substance called tricalciumphosphate (TCP). Has this fact relation to the deleterious effect of such “mixed” coatings? The authors do not know and recommend further investigation.

But they also say that the present results do not justify the “extra economic burden” that the use of HA coated total hips imply!

Information for you:

This study pointed a finger on one expensive innovation that probably backfired. Instead of improving the results, the HA coating used on the three investigated total hip models caused considerable increase of failures. Unfortunately, this report has too many “but”, caused by bad registration of important risk factors to produce a general warning. It seems, however, also from other published results that HA coating offers no decisive advantage over non-coated, porous coated models.

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References

Lazarinis S. et al.: Increased risk…..Acta Orthopaedica 2009, 80, x-x

O5/01/2010

PROPHYLAXIS AGAINST DVT – WHEN THE AUTHORITY RECOMMENDS

Read also the chapter Deep vein thrombosis

Drugs that should prevent development of clots in deep veins are big business. Deep vein thrombosis (DVT) is seldom a problem in itself, as the majority of these thrombi resolves / dissolves spontaneously. In a small percentage of patients, however, these thrombi will travel into the lung, producing potentially lethal pulm emboli (PE). That potentially lethal but very rare event is the reason why the use of prophylactic drugs is recommended for patients operated on with total joint replacement in the lower extremity.

These dugs, however, have side effects, sometimes also lethal (bleeding, thrombocytopenia). Not to wonder, that many surgeons are not willing to replace one risk (PE) with another risk (bleeding.

And here come authorities with their recommendations, so called guidelines They recommend the prophylactic regime that combines maximal benefit (in saving patients’ lives and State’s money) with the minimal risk of side effect.

As the prophylactic drugs against DVT are steadily developing, so are also developing these guidelines.

In England there is a special government institution that recommends the best methods of prophylaxis and treatment. This institution NICE) issued 2007 guidelines for prophylaxis against DVT for patients undergoing total hip (TH) and total knee (TK) surgery. These guidelines recommended the use of low molecular weight heparin (LMWH) for all patients undergoing TH and TK surgery during their stay in the hospital and for patients >60 years of age for further four weeks after discharge.

NICE estimated that adherence to these guidelines will reduce the rate of DVT, pulmonary embolism, and save £4 million to the National Health System.

What was the reality?

A group of British statisticians and surgeons followed 220 000 patients operated on with TH and TK to determine the rates of complications for a 12 months period both before and after the publication of these guidelines (Jameson 2010)

The use of the LMWH increased “significantly” from 60 to 68 % following the publication of the guidelines. But also the number of dangerous side effects of LMWH increased “significantly” (from 0,11% to 0.16%). And the number of DVT rose also significantly! (Although there the rise was only from 1.69% to 1.84%).

The authors conclude: The recommendations from NICE are based on predicted reduction in (DVT)… reducing…mortality and costs to the NHS. The early results (of the adherence to NICE guidelines) do not support these predictions but do show an increase in complications.

Information for you: This is a history “as usual” when the government is involved. The wishful predictions on the preventive effect of LMWH against DVT were based on scientific reports published in scientific journals by scientists paid by pharmaceutical companies. The side effects of the LMWH drugs in these reports “received little attention” as the authors expressed the fact that the pharmaceutical companies did not wish to scare the doctors with such reports. NICE acknowledges that there are no “accurate estimates of venous thromboembolic risk in the modern era”. Who should then be subjected to the risk of side effects of the drugs against DVT?

New and better drugs are under development; just NICE did not manage to evaluate them. Until then discuss with your surgeon the question of prophylactic against DVT carefully. If you are a patient with little or no risk of DVT it may perhaps suffice with only mechanical prophylaxis or no prophylaxis at all.

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References:

Jameson S.S. et al.: The impact of national guidelines for the prophylaxis…J Bone Joint Surg – Br 2010; 92-B: 123 -9

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