NEWS

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

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