Articles 2010

Smith & Nephew Press Conference about the Safety and Effectiveness of Hip Resurfacing with the BHR -
Birmingham Hip Resurfacing Device

Review by Patricia Walter

May 6, 2010

Introduction: Joseph M. DeVivo, President of Smith & Nephew Orthopaedics

Joseph M. DeVivo, President of Smith & Nephew Orthopaedics (NYSE: SNN, LSE: SN), the maker of the BHR Hip introduced the press conference and discussed the safety and effectiveness of the BHR.  He explained that over 125,000 patients worldwide have received a BHR since 1998. The BHR and the issue of metal sensitivity in patients with MOM (metal on metal) implants will be discussed. The purpose of this event is to deliver specific facts about the BHR and its unrivaled track record of success for active patients around the world.

Mr. DeVivo explained that information about hip resurfacing presented at the 2010 American Academy of Orthopedic Surgeons will be discussed.  Recently, there has been negative information in the press about metal on metal devices which includes hip resurfacing devices like the BHR.  The press has taken the failures of a few to cast doubts about all hip resurfacing.   It has omitted the successes of hip resurfacing and that 7 out of 10 surgeons performing hip resurfacing choose the BHR.  Smith & Nephew feel the BHR is a safe and effective device providing successful hip resurfacing for patients worldwide.

Derek McMinn, MD, British surgeon and inventor of the BHR

Derek McMinn, MD, pioneering British surgeon and inventor of the BHR hip explained that the BHR has been proven successful by peer review data and his own clinical data. There are four main pieces of evidence that show the success of the BHR:

1.   The Australian Orthopaedic Association's National Joint Replacement Registry - tracked every hip resurfacing since 1998.  Less than 1/3 of 1 percent of hip resurfacing failures are caused by an adverse tissue reaction.

2. In a 9 center Canadian study presented at the recent 2010 AAOS, 3 resurfacing patients out of 3400, less than 1/10 of 1 percent, experienced a tissue reaction.

3. Long Term data, from the Owestry outcome center, tracked 5000 BHR patients and now 518 BHR patients at 10 years of follow up. The study was carried out by 18 surgeons in 16 different countries. There was a 95% success rate at 10 years.

4.  Mr. McMinn’s own clinical data started in 1997.  He performed 3095 BHRs until end of 2009.  At 12 years follow up, he has a 96% survivorship.

Therefore, according to McMinn, those 4 pieces of data from a large number of surgeons and his own clinical experience shows the BHR works.  There have been adverse reactions reported in all of the studies, but these numbers are incredibly small. However, since MOM resurfacing has been going on in UK since 1991, when he did his first resurfacings, there have been a number of adverse reactions reported. One study from Oxford has over 30 presentations or publications of pseudotumors.  In 2008, one percent of their patients were affected by this condition. Mr. McMinn explained that we need to examine what has happened in Oxford. They presented and published 610 BHRs in 2008. Those patients were operated on by 7 consultants and 30 trainees resulting in a large input from inexperienced surgeons. We know, explained McMinn, from a presentation from the last academy meeting that they have reported on poor surgery. The inclination angle of the cup should be 40 degrees; however, the Oxford pseudotumor group reported angles from 10.1 to 80.6 degrees.  I need to stress, the high inclination angles up to 80.6 angles are completely unacceptable. Every BHR, Metal on Metal, Ceramic on Ceramic and metal on poly device will fail with that type of poor surgery.  

McMinn explains that the adverse reactions for hip resurfacing are reported from 2 categories:

1. Poor results from well established BHRs put in badly causing edge loading, high metal wear and an adverse tissue reaction to lots of debris.

2. Poor results from implants that don’t work. The  4^th generation devices such as the Durom and ASR devices have both been associated with much higher failure rates than the BHR both on individual surgeon reports and Australian national registries. The adverse tissue reactions to the ASR are particularly prevalent. The UK reports around 7% revision rate for ASR resurfacing.  ASR THR mom failures are also double than other devices.  So the UK regulatory bodies are faced with reports of devices that are poor and adverse tissue reactions by well established devices put in badly.

Edwin Su, MD, of the Hospital for Special Surgery

Edwin Su, MD, of the Hospital for Special Surgery, agreed about the importance of hip resurfacing in the lives of patients.    After training with Mr. McMinn and Dr. Amstutz, he has completed over 1300 hip resurfacings with majority being BHRs.  I can say with authority that this procedure can be a life restoring event for the patients. Metal on Metal hip resurfacing done with precise technique and a well designed implant can work.  In appropriate patients, hip resurfacing can achieve nothing short of miraculous life changing results.  Hip resurfacing allows patients to return to active pain free lives. Certain patient types do better with resurfacing than others.  Good solid bone stock means you will do well.  Poor bone stock means there is an elevated risk of a femoral neck fracture. This is common knowledge    Patients under age 65 have best bone stock.  92.7% of all resurfacings are in patients under 65.  Patient selection is very important.  The data shows men do better than women.  Women require smaller components and are more difficult to align during surgery.  Also women’s bones are less dense, so some women are not ideal candidates for hip resurfacing. Australian shows 80% resurfacings are in men.  Resurfacing works better in men than women. Women of child bearing years are not recommend to have hip resurfacing.

Dr. Su explained about the issue of Implant alignment.  If the components are misaligned, there will be an increased risk of metal wear because the surfaces will not be properly lubricated during regular physical activity. There is a resulting risk of adverse tissue reactions and possible revision surgery.  Although this is true for most hip replacement surgery, it is especially true for resurfacing since the implants are less forgiving due to their precise manufacturing.  This rate of adverse tissue reactions is extremely rare in resurfacing and less than ½ of 1 percent.

The literature, explained Dr. Su, shows experienced surgeons who have undergone appropriate training, can place a hip resurfacing device correctly.  A surgeon not doing them on a regular basis has a greater chance of not achieving optimal results. It’s that simple explained Dr. Su.   This is true in any surgery in any specialty. While some implants perform better than others, good outcomes with hip resurfacing most often are achieved by experienced surgeons who have received excellent training and are careful in patient selection.  Dr. Su has offered hip resurfacing since 2006 and has seen spectacular results since then.

Scott Marwin, MD, an orthopedic surgeon with New York University's Hospital for Joint Diseases

Dr.  Marwin explained that the use of the BHR, after 12 years use worldwide and 4 years use in the states, remains an exciting option for some patients.  It has never been suggested for all hip replacement surgery.  Fewer than 10% of all patients are candidates.  Fundamentally, it is a bone conserving procedure and saves a significant amount of healthy bone.  Preservation of the basic structure of femur retains the natural size and angles of the joint and reduces any possibility of leg length discrepancy after surgery.  Also patients’ soft tissue doesn’t have to adjust to a different set of shapes and kinematics that comes with a THR. Many patients forget which side has the BHR implant.  Hip resurfacing also retains the patient’s anatomy which decreases the possibility of a dislocation. In a THR, the long metal neck can act like a lever on the edge of the metal cup and dislocate the ball out of the socket.   The natural femoral neck retained during hip resurfacing means incidence of dislocation is extremely rare.  If a resurfacing patient needs a revision, they can receive a matching THR component to match the existing cup.  Hip resurfacing reduces wear and leads to a longer life for the implant as compared to a THR.  Dr. Marwin has implanted more than 750 hip resurfacing devices and can see what they can do for the active patient.

 

Summary by Joseph M. DeVivo

 The BHR is different than other MOM devices on the market that are not performing up to standard. The BHR outperforms the gold standard for THRs in the core patient age group. Hip resurfacing gives patients their active life style back.  BHR preserves so much healthy bone that it feels like a normal hip. More information can be found a www.hipsresurfacing.com

Question and Answers from Audience

Question:  Terry Stanton, AAOS.  Concerning the medical device alert in Britain - is it warranted and correctly crafted?

Answer: Dr. Su - It casts a general concern over MOM usage, but does not speak specifically to the BHR.  BHR has its own clinical data and has not produced the type of concern other MOM device have.  It stands on its own according to worldwide sources.

Q: Surgeon inexperience and poor technique – more globally in the US, what factor will it play?

A:  Dr. Su - Where the BHR is concerned, as part of the FDA approval, it has mandated a very high level of training.  Every surgeon is trained to same protocol.

Q: Canadian Study presented in New Orleans – follow up was 3 years. Comment on how solid the evidence is since the follow up is shorter.

A.  Mr. McMinn - Important to look at what happens in first 3 years in hands of a new group of surgeons to hip resurfacing.  The Oxford Group is reporting adverse reactions to metal debris in the early years. It is highly significant how a new group of trained surgeons get on.  The fact that there are an incredibly low number of incidents of adverse reactions in a 9 center study with over 3000 patients speaks volumes for the devices and training of the surgeons.  The longer term results are more important. The Australian registry has over 8000 people with an incredible low incidence of adverse reactions with survivorship at  95% for BHR at 8 years.  The Oswestry registry with 518 patients at 10 years, shows a  95.4% implant survivorship.  Phenomenally good results.  In my own group, adverse reactions have occurred in 0.3% of my whole group.  Out of 3095 BHR patients thru 2009, there were 10 adverse reactions.  Unlike the Oxford Group, all the revisions have been fine. None were associated with soft tissue destruction.  These were in the main, fluid collections requiring a bearing change to solve the problem. The patient made a totally uncomplicated recovery.  I saw adverse reactions much later.  Oxford was showing them 2 or 3 years after surgery. 

Q. Metal sensivity and pseudotumros are always curious problems.  In terms of devices, is there is less metal release in different devices?

A. Mr. McMinn - It is very clear who gets the pseudotumors. The retrievals from the Oxford Group show pseudotumors were associated with aged wear of the acetabular cup.  With normal lubrication and normal wear, there are no pseudotumors.  Clearly,  if you want a MOM device to fail,  implant it badly or design it badly so you get age loading and age wear which results in a high metal volume of debris early on.

Does commitment to rehabilitation influence the clinical outcome of total hip resurfacing arthroplasty study 2010

Link to original medical study

The purpose of this study was to evaluate whether compliance and rehabilitative efforts were predictors of early clinical outcome of total hip resurfacing arthroplasty.

Methods: A cross-sectional survey was utilized to collect information from 147 resurfacing patients, who were operated on by a single surgeon, regarding their level of commitment to rehabilitation following surgery. Patients were followed for a mean of 52 months (range, 24 to 90 months).

Clinical outcomes and functional capabilities were assessed utilizing the Harris hip objective rating system, the SF-12 Health Survey, and an eleven-point satisfaction score. A linear regression analysis was used to determine whether there was any correlation between the rehabilitation commitment scores and any of the outcome measures, and a multivariate regression model was used to control for potentially confounding factors.

Results: Overall, an increased level of commitment to rehabilitation was positively correlated with each of the following outcome measures: SF-12 Mental Component Score, SF-12 Physical Component Score, Harris Hip score, and satisfaction scores.

These correlations remained statistically significant in the multivariate regression model.

Conclusions: Patients who were more committed to their therapy after hip resurfacing returned to higher levels of functionality and were more satisfied following their surgery.

Author: David MarkerThorsten SeylerAnil BhaveMichael ZywielMichael Mont
Credits/Source: Journal of Orthopaedic Surgery and Research 2010, 5:20

The controversy regarding adverse wear in metal-metal bearings

Thomas P. Gross , MD 3/5/2010

I have used over 3000 metal bearings in primary total hip and hip resurfacing as well as revision surgery. I have revised 2 for adverse wear 7 years after implantation. I know that most other high volume hip resurfacing surgeons have a similar experience. The revisions were straightforward and the patient enjoyed the same rapid and complete recovery as if she had a primary hip replacement.

Currently less than 5% of my practice involves revision surgery. However, I have revised over 100 metal plastic replacements for excess wear. Furthermore significant wear related damage to the tissues is seen in virtually all metal plastic hip replacement or knee replacement revised for other causes.

A surgical group that has seen a surprisingly large number of wear‐related failures of metal bearing implants has coined the term "pseudotumor" when an inflammatory soft tissue mass is seen around the hip of a metal bearing implant. However, this inflammatory soft tissue reaction to metal wear debris is not much different than the inflammatory reaction that we have seen with plastic wear debris for many years.

All artificial bearing implants give off wear particles. The question is, which type of wear debris is best tolerated by the body? During the last 20 years of joint replacement polyethylene osteolysis (bone destruction caused by plastic wear debris) has been a major problem. But anyone who has revised total joints is also aware that polyethelene debris also is always associated with large amounts of soft tissue reaction around the joint. Polyethelene has been improved, and metal bearings have been developed. Both give off much less wear debris than the old polyethelene implants. The question is which results in less wear related damage? At this point we do not yet have the answer. Adverse wear reaction is a serious problem, but fortunately it is very rare.

Lets put this into perspective. The most common reason resulting in revision of total hip replacements in the US is hip instability (recurrent dislocation). 20% of all hip revisions are done for this reason. This is far more common than adverse wear reaction. Hip instability is a very disabling condition that occurs in 3‐5 % of hip replacements. The rate of instability for large head metal bearings is less than 1/2 %. Larger bearings are the solution for this problem. Large head metal bearings (resurfacing and total hip) are currently the only ones that allow reconstructing the hip in a biomechanically normal fashion to avoid instability. Proponents of plastic and ceramic bearings realize this and have made their bearings thinner recently to allow larger heads to be inserted (32‐36mm). This has made them more stable, but 32‐36mm does not yet approximate normal femoral head sizes in the average female (48mm) and average male (52mm) patients. These larger head (32‐36mm) implants for plastic and ceramic bearings have only been in use for a few years and it is not yet clear if these bearings will break at a higher rate because they are thinner. I would not recommend impact sports on thin plastic and ceramic bearings. Anatomic sizing that matches the patient's own size is only possible with large metal head designs. These are stable and can tolerate repetitive full impact without breaking. Wear rates are not significantly increased by running.

In the last few years we have learned that these rare cases of adverse wear in metal bearings are related to three factors: steep acetabular inclination greater than 55 degrees, small component sizes, certain component designs with an extremely shallow arc of coverage. At this point it is still only a very tiny percentage of patients with cup inclination angles above 55 degrees that have had wear problems. If a patient with an inclination angle above 55 degrees develops symptoms years after surgery, I would first check metal levels and an MRI. If the levels were high or a soft tissue mass developed I would recommend revision. So far this has happened twice in my practice.

More important, however, is prevention of this adverse wear complication. Since this information about cup inclination has become available several years ago we developed and tested a protocol for measuring the inclination by XR during the operation. The paper reporting this technique will be published in CORR this year. Using this technique in every case, I now have had no cups implanted with inclination greater than 55 degrees since 10/ 2007. We expect that this technique will completely eliminate this rare cause of failure in metal bearing hip implants: adverse wear reaction.

Antibiotic Prophylaxis for Bacteremia in Patients with Joint Replacements by AAOS

February 2009 American Academy of Orthopaedic Surgeons

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This statement provides recommendations to supplement practitioners in their clinical judgment regarding antibiotic prophylaxis for patients with a joint prosthesis. It is not intended as the standard of care nor as a substitute for clinical judgment as it is impossible to make recommendations for all conceivable clinical situations in which bacteremias may occur. The treating clinician is ultimately responsible for making treatment recommendations for his/her patients based on the clinician’s professional judgment.

Any perceived potential benefit of antibiotic prophylaxis must be weighed against the known risks of antibiotic toxicity, allergy, and development, selection and transmission of microbial resistance. Practitioners must exercise their own clinical judgment in determining whether or not antibiotic prophylaxis is appropriate.

More than 1,000,000 total joint arthroplasties are performed annually in the United States, of which approximately 7 percent are revision procedures.1 Deep infections of total joint replacements usually result in failure of the initial operation and the need for extensive revision, treatment and cost. Due to the use of perioperative antibiotic prophylaxis and other technical advances, deep infection occurring in the immediate postoperative period resulting from intraoperative contamination has been markedly reduced in the past 20 years...

...Patients with joint replacements who are having invasive procedures or who have other infections are at increased risk of hematogenous seeding of their prosthesis. Antibiotic prophylaxis may be considered, for those patients who have had previous prosthetic joint infections, and for those with other conditions that may predispose the patient to infection. There is evidence that some immunocompromised patients with total joint replacements may be at higher risk for hematogenous infections. However, patients with pins, plates and screws, or other orthopaedic hardware that is not within a synovial joint are not at increased risk for hematogenous seeding by microorganisms...

...Given the potential adverse outcomes and cost of treating an infected joint replacement, the AAOS recommends that clinicians consider antibiotic prophylaxis for all total joint replacement patients prior to any invasive procedure that may cause bacteremia.

The Influence of Head Size and Sex on the Outcome of Birmingham Hip Resurfacing

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 The Journal of Bone and Joint Surgery (American). 2010
Callum W. McBryde, MD, FRCS(Tr&Orth)1, Kanthan Theivendran, MRCS1, Andrew M.C. Thomas, FRCS1, Ronan B.C. Treacy, FRCS(Tr&Orth)1 and Paul B. Pynsent, PhD1

1 Research and Teaching Centre, Royal Orthopaedic Hospital, Bristol Road South, Northfield, Birmingham B31 2AP, United Kingdom. E-mail address for C.W. McBryde: cwmcbryde@hotmail.com

Investigation performed at the Royal Orthopaedic Hospital, Birmingham, United Kingdom

Background Hip resurfacing has gained popularity for the treatment of youngand active patients who have arthritis. Recent literature has demonstrated an increased rate of revision among female patients as compared with male patients who have undergone hip resurfacing. The aim of the present study was to identify any differences in survival or functional outcome between male and female patients with osteoarthritis who were managed with metal-on-metal hip resurfacing.

Methods A prospective collection of data on all patients undergoing Birmingham Hip Resurfacing at a single institution was commenced in July 1997. On the basis of the inclusion and exclusion criteria,1826 patients (2123 hips, including 799 hips in female patients and 1324 hips in male patients) with a diagnosis of osteoarthritis who had undergone the procedure between July 1997 and December2008 were identified. The variables of age, sex, preoperative Oxford Hip Score, component size used, surgical approach, lead surgeon, and surgeon experience were analyzed. A multivariate Cox proportional hazard survival model was used to identify which variables were most influential for determining revision.

Results The mean duration of follow-up was 3.46 years (range, 0.03 to10.9 years). The five-year cumulative survival rate for the655 hips that were followed for a minimum of five years was 97.5% (95% confidence interval, 96.3% to 98.3%). There were forty-eight revisions. Revision was significantly associated with female sex (hazard rate, 2.03 [95% confidence interval,1.15 to 3.58]; p = 0.014) and decreasing femoral component size hazard rate per 4-mm decrease in size, 4.68 [95% confidence interval, 4.36 to 5.05]; p < 0.001). Revision was not associated with age (p = 0.88), surgeon (p = 0.41), surgeon experience (p = 0.30), or surgical approach (p = 0.21). A multivariate analysis including the covariates of sex, age, surgeon, surgeon experience, surgical approach, and femoral component size demonstrated that sex was no longer significantly associated with revision when femoral component size was included in the model (p = 0.37).Femoral component size alone was the best predictor of revision when all covariates were analyzed (hazard rate per 4-mm decrease in size, 4.87 [95% confidence interval, 4.37 to 5.42]; p <0.001).

Conclusions The present study demonstrates that although female patients initially may appear to have a greater risk of revision, this increased risk is related to differences in the femoral component size and thus is only indirectly related to sex. Patient selection for hip resurfacing is best made on the basis of femoral head size rather than sex.

Surgery hits hip pocket

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By Sue Dunlevy From: The Daily Telegraph January 04, 2010

ONE in every 12 hip and knee replacements need corrective operations and new surgical techniques are more susceptible to problems, according to Australia's largest health insurer. Medibank Private has reviewed its data on the 3990 hip replacements and 4860 knee replacements it paid for in 2008 and found "on average surgeons perform revisions on 8.3 per cent of their total procedures"...

...The National Joint Replacement Registry, which is studying the reliability of hip and knee replacements, has found newer joint replacements that are cementless or hybrid are more likely to need further surgery than the older cemented replacements...

...And research found the more reliable cement joint replacements are used in just 23 per cent of hip replacement operations...

...The latest report from the National Joint Replacement Registry found that three types of hip replacements - the ASR, Durom and Recap hip replacements - had more than twice the risk of revision of other resurfacing prostheses. Hip replacements with smaller femoral head sizes are also more likely to be revised.

The Allegretto knee, one of the most common knee-replacements used in Australia, has a 10 per cent revision rate at 2.5 years, which is considerably greater than other similar prostheses.