HR Issues

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.

New Data Reinforces the Proven Safety and Effectiveness of the BIRMINGHAM HIP Resurfacing System

80-percent of US surgeons choose the BHR hip as it outperforms all other metal-on-metal resurfacing devices

MEMPHIS, Tenn., May 3 /PRNewswire-FirstCall/ -- Recent new data(1) presented at this year's American Academy of Orthopaedic Surgeons (AAOS) annual meeting reinforces the BIRMINGHAM HIP™ Resurfacing (BHR) System as a safe and effective hip resurfacing device. The multi-site study, performed by orthopedic surgeons practicing at nine Canadian academic centers, showed that three years after surgery, 99.91% of their 3,400 hip resurfacing patients experienced no implant failure due to metal wear debris. The BHR Hip was the most used resurfacing device in this study.

This week, the Hospital for Special Surgery (HSS) in New York City will be holding a medical education course titled "Total Hip: Replacement and Resurfacing" on May 7 and 8 for leading hip surgery specialists from across the U.S. Chairing the course will be Edwin Su, MD, of the Hospital for Special Surgery, and the teaching faculty will include pioneering British surgeon Derek McMinn, MD, inventor of the BHR hip.

During a press conference and Q&A webcast on Thursday, May 6, at 3 p.m. US EDT, 8 p.m. GMT, Joseph M. DeVivo, president of Smith & Nephew Orthopaedics (NYSE: SNN, LSE: SN), the maker of the BHR Hip, will be joined by Dr. Su and Mr. McMinn, as well as Scott Marwin, MD, an orthopedic surgeon with New York University's Hospital for Joint Diseases. The panel will review current data confirming the safety and effectiveness of hip resurfacing and the BHR Hip. Smith & Nephew Orthopaedics will host the call, and additional details are at the bottom of this release.

The new study recently presented at the AAOS meeting aligns with previously released BHR Hip data from other prestigious sources and further addresses the metal wear debris concerns raised about metal-on-metal hip implants.  The BHR Hip's track record for longevity remains unchallenged in the literature, as well. These sources include:

• The Journal of Bone and Joint Surgery published in January of this year a study tracking 155 consecutive BHR patients over three years. The data showed no revisions of BHR Hips due to metal wear, but patients who received a competing metal-on-metal resurfacing device were revised within three years of surgery at a rate of 3.4-percent due to adverse tissue reactions.(2)
• The Australian Orthopaedic Association's 2008 National Joint Replacement Registry, a record of nearly every hip implanted in that country over the previous 10 years, tracked 6,773 BHR Hips and found that less than one-third of one-percent may have been revised due to the patient's reaction to the metal component.(3)  
• The Australian Registry hip resurfacing data for 2009, 70-percent of which comes from BHR Hip procedures, indicates that for men under age 65, hip resurfacing performs at the same or a better rate than total hip replacement. This registry also shows that the BHR Hip remains successful in 95-percent of cases eight years after surgery, whereas no other implant performs better than 94.7-percent just five years after surgery.(4)
• Great Britain's Oswestry Outcomes Centre's patient registry,  which tracked 5,000 BHR Hips implanted by 148 different surgeons in 37 countries over 10 years (1998-2008), reports that the BHR Hip remains successful in 95.4-percent of all patient segments 10 years after surgery. This registry also reported that 98.6-percent of patients were "pleased" or "extremely satisfied" with their BHR Hip implants 10 years after their resurfacing procedure.(5)
• Mr. McMinn's clinical data, based on 3,095 hip resurfacing patients implanted between 1997 and 2009, shows that more than 12 years after surgery, the BHR hip remains successful in 99-percent of men aged 60 and over, and 97-percent for men under age 60.

"The BHR Hip's outcomes are remarkable when compared to other resurfacing devices," said Dr. Marwin. "The depth and consistency of the data collected globally shows the BHR Hip is truly different."

"For the right patients in my practice, hip resurfacing has proven to be an excellent choice," said Dr. Su. "They have extremely high levels of satisfaction after returning to their regular lifestyle."

To explain the patient advantages seen consistently in the literature, surgeons indicate the key differences between the BHR Hip and other resurfacing devices are its metal composition, its design geometry and its surgical instrumentation.

The BHR Hip has a unique metallurgy heritage which goes back more than 30 years and includes a first-generation metal-on-metal resurfacing process which contributes to long-term survivorship of BHR Hip recipients.

Additionally, the BHR Hip's design geometry replicates the natural hip's ability to pull the body's own joint fluids into the ball and socket interface, which is believed to be another source of its best-in-class performance.

Of particular importance during hip resurfacing surgery is the correct positioning of the acetabular cup, or hip socket. When this component is not properly aligned, studies show that metal wear can accelerate and resurfacing devices can fail before their time.  Surgeons believe that the instrument used to implant the BHR Hip is simpler and more accurate than other devices' instruments, and may contribute to its success.

"Just like the lubricating barrier in a healthy hip, there is a natural fluid layer between the femoral head and the cup that the two metal surfaces glide across during physical activity," said Mr. McMinn. "If the surgeon malpositions the acetabular cup causing edge loading, the lubrication is lost. It's equivalent to running a car engine without lubrication oil. High wear will occur, resulting in premature failure. Overall, it is a combination of the metal composition, the design and the quality of the surgical technique that makes the BHR Hip the safest resurfacing implant on the market."

"The bottom line is that the BHR Hip is not like other metal-on-metal hip implants," said DeVivo. "Not only does it have the longest track record of any resurfacing device, but the most esteemed medical literature shows it outlasts other implants. It's in a class all its own – it's safe and effective, and is the best choice for active patients."



Footnotes

(1) Beaule PE, Smith FC, Powell JN et al. A Survey on the Incidence of Pseudotumours with MOM Hip Resurfacings in Canadian Academic Centres. Podium presentation # 665. Proceedings of the American Academy of Orthopaedic Surgeons Annual Meeting, New Orleans LA. 2010

(2) Langton DJ, Jameson SS, Joyce TJ, Hallab NJ, Natu S, Nargol AVF.  Early failure of metal-on-metal bearings in hip resurfacing and large-diameter total hip replacement, A CONSEQUENCE OF EXCESS WEAR. J Bone Joint Surg Br. 2010; 92-B: 38-46

(3) Table HT 46. Australian Orthopaedic Association National Joint Replacement Registry Annual Report. Adelaide: AOA; 2008.

(4) Table HT 46. Australian Orthopaedic Association National Joint Replacement Registry Annual Report. Adelaide: AOA; 2009.

(5) Robinson E, Richardson JB, Khan M. MINIMUM 10 YEAR OUTCOME OF BIRMINGHAM HIP RESURFACING (BHR), A REVIEW OF 518 CASES FROM AN INTERNATIONAL REGISTER. Oswestry outcome centre, Oswestry, UK.

About Us

Smith & Nephew is a global medical technology business, specialising in Orthopaedics, including Reconstruction, Trauma and Clinical Therapies; Endoscopy and Advanced Wound Management.  Smith & Nephew is a global leader in arthroscopy and advanced wound management and is one of the leading global orthopaedics companies.

Smith & Nephew is dedicated to helping improve people's lives.  The Company prides itself on the strength of its relationships with its surgeons and professional healthcare customers, with whom its name is synonymous with high standards of performance, innovation and trust.  The Company operates in 32 countries around the world.  Annual sales in 2009 were nearly $3.8 billion.

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A Modified Posterior Approach Preserves Femoral Head Oxgenation During Hip Resurfacing 2010

Steffen RT, De Smet KA, Murray DW, Gill HS  2010 Mar 22

Original Link  http://www.ncbi.nlm.nih.gov/pubmed/20334994?dopt=AbstractPlus

Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Oxford, UK.

In 11 patients, the oxygenation was measured in the superolateral quadrant of the femoral head during resurfacing with a modified posterior approach, designed to preserve the blood supply, using a gas-sensitive electrode. These were compared with measures from 10 patients in whom the standard posterior approach was used. The modified approach patients maintained a significantly (P < .005) higher amount of relative oxygenation after the approach, 78% (standard deviation [SD], 45%) vs 38% (SD, 26%), and acetabular component implantation, 74% (SD, 56%) vs 20% (SD, 28%). The modified posterior approach, unlike the standard extended approach, does not significantly compromise the blood supply to the head; and we recommend this approach be considered for hip resurfacing.

Mr. Bloomfield responds to the The Times Article: "Is hip resurfacing the best  solution for arthritis?"

Let's start at the beginning!

Fact No. 1 : Nothing is as good as nature's own. Nothing can ever replicate the perfection of your native, original hip - before it became diseased. One day, maybe we can grow you a new one, then this debate will be irrelevant. Everything else is a compromise. Some compromises are better than others, and it depends on the individual patient, their activity or age, as well as the experience of the surgeon and the quality of components used.

Fact No. 2: However you 'spin' it, Conventional total hip replacement or THR is effectively an amputation of the head & neck of the femur. No if's and's or but's. Once it is gone, that's it, no going back. So, even if hip resurfacing [I call it BHR as I only use the Birmingham device] has a SLIGHTLY higher failure rate than THR, it is still worth thinking about the preservation of your femoral head & neck. The younger or more active you are, the more important this thought becomes.

Fact No. 3: The article only looks at revision rates when comparing BHR to THR. It says nothing about other, more subtle problems with THR like dislocation. OK, dislocation maybe rare with THR and almost unknown with BHR, but it is still a great concern in the early recovery phase. The fear of dislocation with THR drives the rehabilitation in the first few weeks and greatly restricts the advice the surgeon can give patients. Patients have to be given guidance to avoid dislocation which is often more onerous than is strictly required so that everyone can 'cover their backsides' so to speak. With BHR, my team is now [or should be!] telling MOST patients there are no special or onerous restrictions. Patients can sleep on their sides. They do not need raised toilet seats at home. They do not need to worry about dislocation because it is almost impossible. It allows the patient to recover full range of motion earlier and more safely. Unless there are concerns about bone quality, patients can be told to get back to activities of daily living as fast as their body allows. The only thing we have to be a bit cautious about is high impact stuff like running or jogging, football, rugby, skiing and the like. These can be allowed after the 3 or 4 month x-ray and if surgeon is happy that the danger of neck of femur fracture has passed.

The other, very subtle and impossible to quantify downside of THR is that surgical invasion of the femoral medullary canal forces marrow contents into the bloodstream. The bone marrow of the long bones is where your body makes all your blood cells. Red ones, white ones and platelets. It is why dogs love the marrow of a bone so much - it is rich in fat and protein. Forcing this marrow fat, rich in immature blood cells and other proteins, triggers an inflammatory cascade in the leg around the whole length of the femur and in the lungs which filter the globules before they would enter the circulation to the brain or other major organs. When severe, this phenomenon is called fat embolism. BHR dramatically reduces this embolisation phenomenon and is why I feel quite happy doing bilateral BHR when the patient has bilateral disease, but I would be very, very careful or wary of bilateral THR on the same day. In fact I tried bilateral THR several times before BHR came along and had lots of trouble. Done over 30 cases of bilateral BHR now and never regretted it. A truly astonishing operation as patients take only one or 2 more days to go home as compared with a single side BHR. i.e the recovery time is not doubled.

Fact No. 4: Some of us have always instinctively realized this, but BHR is exquisitely sensitive to accurate component positioning, and the exact metallurgy/manufacture of the components. THR can be put in quite sloppily and still work. At least for more than the 3 years the Times article is looking at. The figures in the UK National Registry are for all surgeons, using all the currently available hip resurfacing prostheses in varying mix. One should look ONLY at high volume, experienced surgeons to get the true picture. I wish I had the time and energy to look in detail at my own series, but it is certainly less than 4% failure at 3 years! The other trouble is that McMinn has already published large, detailed series so does the world need yet another one? McMinn's own figures, particularly in the under 55's are so good, many thought he must have fabricated them. I think less than 1% 'failure' at 5 years, not 3 years. This is the problem with raw statistics: they are so easily used like a drunk man uses a lamppost - more for support than illumination.

So much of the 'failure' we are looking at is due to poor surgery, poor prostheses or a combination of both. Women are only more at risk because their hips tend to be smaller, therefore the precise positioning of components is more critical. Women also tend to naturally have slightly weaker or less dense bone than men, so their cups may not integrate as planned or they may fracture through the neck of the femur. Apart from that, I personally don't believe there is any great gender difference.

Fact No. 5 ALVAL or metal ion 'allergy' is very, very rare. Irritation from excessive metal wear from poorly positioned or poorly manufactured prostheses accounts for the vast majority of the so-called ALVAL being reported. It sounds to me like Andrea had excessive metal wear leading to predictable irritation, fluid accumulation around the hip, and pain. Andrea, I do not think you had true ALVAL. Indeed your surgeons tend to confirm this as they did not find the masses of inflammatory tissues and destruction that would have been present if you had true ALVAL. The Melissa test is useless for predicting who will get ALVAL. The Melissa test has been used to justify large scale extraction of dental fillings from people, particularly in Scandinavia, on the basis that allergy to the metal in the fillings was making these people ill. Mass hysteria on a quite fascinating scale, and remember for very tidy profit. ALVAL is not confined to BHR. It is a problem with any metal-on-metal bearing couple. If ALVAL is used as a reason to discredit BHR, then all metal on metal bearings would have to be suspect. Which would leave only metal or ceramic on polyethylene, or ceramic on ceramic.

So lets look at metal or ceramic on polyethylene. Polyethylene is basically like hardened wax. Soft and slippery. Under pressure and when heated, it deforms or flows, just like melting wax. You can make the wax a bit harder, but it is still wax. There are constantly new or improved polys on the market. We have been here before. Let's look at Hylamer, a trade name from De Puy:

Hylamer polyethylene was introduced in the 1990s as an alternative to conventional polyethylene. Its chemical and physical properties, and especially its high crystallinity, were claimed to improve resistance to wear. Initially Hylamer devices were sterilized by gamma radiation in air, then the technique was changed and gamma radiation was performed in the absence of oxygen. Clinical experience has shown the early loosening of some devices made from Hylamer.

The text understates the problem. Hylamer was an unmitigated disaster and has long ago been withdrawn. So I don't trust poly in any shape or form FOR YOUNG ACTIVE PATIENTS. I still use it for the more elderly and sedentary. It still works perfectly well in this group.

What about ceramic-ceramic? This is the best alternative if you cannot have metal-metal for any reason. BUT some ceramic hips squeak. So loudly they can be heard across a room full of people. Ceramic is brittle and although ceramic fracture is now rare, it still happens and is under-reported. Ceramic ages or oxidises in the body and this can then lead to higher wear rates as the ceramic surfaces lose their shine or surface finish. Finally ceramic-ceramic is a very 'hard' bearing couple with no 'give' or shock absorption. BHR will, in most situations, have a thin film of fluid which can be displaced to absorb shocks at bearing interface.

So, in summary: Yes, BHR will likely ALWAYS have a very slightly higher revision rate than THR at 3 or 5 years, when comparing like for like in terms of young active patients. But the increased risk should be of the order of 1% or less, in the hands of an experienced surgeon. Not the 7 to 14 times quoted. It is the 30 or 40 year comparative results that will tell a different tale!

BHR revision, if ever unfortunately required, will always be easier than THR revision. Pity the poor patient whose THR fails early, or even later, particularly if the femoral side needs to be redone - their surgeon has a much tougher job on his/her hands. And abandoning BHR in favour of THR would mean abandoning all the more subtle advantages of an anatomical-sized component sitting on top of your own preserved femur.

We need to focus on precise surgery, good patient selection, the very best metallurgy and manufacture, not scare ourselves into abandoning the most revolutionary development in the field of hip arthroplasty in the last 50 years.

Mark

A Consensus From The Advanced Hip Resurfacing Course, Ghent, June 2009 About Metal-on Metal Hip Resurfacing

K. De Smet, MD, Orthopaedic Surgeon¹; P. A. Campbell, PhD, Associate Professor²; and H. S. Gill, DPhil, University Lecturer in Orthopaedic Mechanics^{3 1} ANCA Medical Center (AMC-Ghent), Krijgslaan 181, 9000 Ghent, Belgium.
² UCLA/Orthopaedic Hospital, 2400 South Flower Street, Los Angeles, California 90007, USA.
³ Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences University of Oxford, Botnar Research Centre, Nuffield Orthopaedic Centre, Oxford OX3 7LD, UK.

Abstract

We report the consensus of surgical opinions of an international faculty of expert metal-on-metal hip resurfacing surgeons, with a combined experience of over 18,000 cases, covering required experience, indications, surgical technique, rehabilitation and the management of problematic cases.

Introduction

The last decade has seen an increased use of metal-on-metal hip resurfacing arthroplasty as an alternative to contemporary total hip replacement (THR), especially for patients who wish to participate in high-demand activities. Metal-on-metal bearings are also being used more often for THR. In June 2009, the third Advanced Resurfacing Course was held in Ghent, with a faculty that included 21 orthopaedic surgeons whose combined experience included over 18,000 metal-on-metal hip resurfacing arthroplasties. As the meeting served to bring together surgeons, highly experienced in hip resurfacing, from Australia, Europe and the Americas, the opportunity was taken to establish consensus views on issues of required experience, indications, surgical technique and rehabilitation. The aim of this annotation is to disseminate these consensus findings in order to help surgeons who are considering metal-on-metal bearings for both resurfacing and conventional THR. The findings are presented as a majority opinion, with the percentage of the faculty in agreement given in parentheses.

Required experience

The use of metal-on-metal bearings for THR and resurfacing presents a greater technical challenge than that of conventional metal-on-polyethylene bearings. The consensus (81%) was that an orthopaedic surgeon should have a minimum experience of 200 conventional THRs before starting to use a metal-on-metal hip resurfacing arthroplasty. Opinion varied on the number of these operations needed to overcome the learning curve, and ranged from 20 (36%), to 50 (28%) and more than 50 (30%).

Indications

The overall view (100%) was that the ideal candidate for an metal-on-metal hip resurfacing arthroplasty is a relatively young man with normal anatomy and primary osteoarthritis. Being female was not, by itself, a contra-indication (89%), but use of a small femoral head (< 46 mm) was contra-indicated (70%). Being female and wanting to have children was a contra-indication (66%), as was being female and having a metal allergy (70%). Grossly abnormal anatomy, regardless of gender, was also agreed to be a contra-indication (83%). There was considerable debate about bone quality, the general view being that 'good' femoral bone is a prerequisite, but no agreement was reached on a working definition of acceptable quality.

Surgical technique

The majority opinion (56%) was that the best type of femoral placement guide is that which encircles the femoral neck. There was general agreement (63%) that the current acetabular placement jigs are inadequate. The overall preference (78%) was for cementing the femoral component with a thin cement mantle with fixation holes drilled in the femoral bone, use of pulsed lavage, and reduction of the hip in less than eight minutes from the start of mixing the cement.

Rehabilitation

Full weight-bearing can be allowed on the first post-operative day (73%) and patients should use crutches for as long as needed (57%). Six weeks is the optimal time to return to normal non-sporting daily activities (44%), and six months for returning to impact sports such as running or tennis (61%).

Managing problematic cases

It was difficult to achieve a consensus on this topic, and only the broad recommendations of the discussion are reported. It was generally agreed that these patients need to be followed up and those with symptoms investigated. There was no agreement on the diagnostic value of measurements of metal ions, but it was felt that  'high' concentrations of systematic metal ions indicated a problem with the articulation. Cross-sectional imaging and plain radiographs are required for the investigation of a symptomatic metal-on-metal bearing.

It is hoped that these consensus opinions will prove useful to orthopaedic surgeons and will lead to improved outcomes after surgery for hip replacement.

Advice to patients concerning the ASR

I suggest a few points that, I think, everyone can agree to (for any hip, including an ASR):

1. If you have pain or are in any way concerned - go see your surgeon.

2. There are some screening tests. Based on current experience, if blood (or serum) ion levels of Cr and Co are <5ppb, the likelihood a problem with the implant is low. If the level of either is >10ppb, the likelihood of a problem with the implant is increased. In either event, the next step would be an imaging study (ultrasound or MRI) to look for a fluid collection, or a cystic or solid mass - as evidence of an adverse local tissue response.

3. An aspiration of the joint may be appropriate a) to exclude infection as a cause of the joint dysfunction and b) the characteristics of the fluid may help in the differential diagnosis of a problem related to the metal-metal bearing.

I think that the first point is the most important. If you are concerned, go see your surgeon.

Thomas P. Schmalzried, M.D.

I have to start by saying that I have never had any issues with the ASR devise at all. I was very surprised about 6 months ago when the issue of ASR withdrawal first surfaced. There is no doubt that the safety margin for the ASR is lower than other resurfacing systems like the BHR due to a 'low arc of cover'- described by Dr. Desmet. This is because the rim of the cup has become 'non -articular' to accommodate the cup holder. Hence the failure rate is higher than the BHR.

The cups coming loose is certainly not true as I have implanted ASR cups in the most complex of cases. I am 100% confident that it is a technical issue.

It has proven to be an excellent tool in my hands and in dysplasia patients ( CROWE 3)- the s-rom with a ASR cup combination that is hard to beat.

The ASR reamers are very poor and not matched to the ASR cups. I have routinely used BHR or equivalent reamers for the ASR cups for 3 yrs since the time noticed the mismatch between the reamers and cup size for the ASR

The ASR has been excellent tool to provide an anatomical metal on metal articulation in small patients. I am very confident that it will work well if installed correctly. I will surely miss the ASR cup for small made patients if it is withdrawn completely.

with best regards
vijay bose
chennai

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.

Knowing the cause of resurfacing failure can ensure successful conversion to THR by Edwin Su, MD
The shell can be retained in cases involving femoral neck fracture, femoral loosening or impingement.

Read Complete Article by clicking here

March 2010

Causes of failure

"The cause of failure must be carefully assessed prior to the conversion surgery in order to ensure an optimal THR outcome," Su said. He noted that femoral neck fracture is the primary cause of short-term failure in resurfacing procedures. He theorized that the rate of these fractures could be reduced with improved surgical techniques, careful patient selection and preoperative evaluation of bone quality. Inadequate acetabular fixation or the so-called "slipped cup" is another cause of early failure, which may also be related to surgical technique.

"The greatest cause of a mid-term failure is femoral component loosening and osteonecrosis probably plays a role in this," Su said. "I think that component malposition is going to play a large role in these mid-term failures as well." He noted that mid-term investigations of patients with acetabular component malpositioning revealed painful metal reactivity requiring revision.

Other causes of failure include metal hypersensitivity and unexplained pain due to impingement, undetected stress fractures or pseudotumors...

...Shell retention or full revision?

In planning conversion procedures, surgeons have the option of retaining the shell from the hip resurfacing.

"I think this is acceptable for a well-positioned, well-fixed and undamaged shell," Su said. "It is applicable in situations such as, a femoral neck fracture and in a femoral loosening...

..."A full revision is necessary when there is component malposition of chronic duration because there will be damage to the metal components," Su said. "It is also best when there is a question of metal hypersensitivity."

Reference:

• Su E. Surface replacement conversion: Assuring an optimal THR outcome. Paper #44. Presented at the 26th Annual Current Concepts in Joint Replacement Winter Meeting. Dec. 9-12, 2009. Orlando, Fla.
• Edwin P. Su, MD, can be reached at Hospital for Special Surgery, 535 East 70th Street, New York, New York 10021; 212-606-1128;

The status of DePuy Orthopaedics’ ASR platform as Feb. 2010

Last fall of 2009, DePuy decided to discontinue ASR® XL Acetabular Head System and DePuy ASR® Hip Resurfacing Platform (not available in the U.S.) worldwide. As a result of declining demand for the ASR platform and other market factors, DePuy is in the process of phasing out this platform to focus on the development of next generation hip replacement and resurfacing technologies that best meet the needs of surgeons and patients.

DePuy wants to assure patients who have been treated with a device from the ASR platform that there will be options available to them in the future should they need a revision:

· If a patient who had received the DePuy ASR® XL Acetabular Head System for total hip replacement requires a revision surgery, the acetabular component could be revised with the Pinnacle Hip Solutions platform, which would be compatible with an existing well-fixed femoral stem.

· As with any hemi-resurfacing prosthesis, including the DePuy ASR® hemi arthroplasty, a patient requiring a revision procedure would generally be treated with a total hip replacement.

· For patients outside the U.S. treated with DePuy ASR® Hip Resurfacing (not commercially available in the U.S.), DePuy intends to maintain an inventory of ASR XL heads outside the U.S. for use on compatible DePuy femoral stems. This will allow surgeons outside the U.S. the option of retaining a well-fixed ASR Cup when appropriate as part of the revision procedure.

Lorie Gawreluk
Vice President, Worldwide Communications
DePuy, Inc.