Article by Patricia Walter and Hip Resurfacing Surgeons
Patients and prospective patients are always concerned about the complications that could occur after a hip resurfacing surgery. The typical problems include femur neck fractures, dislocations, loose acetabular cups, improperly positioned acetabular cups, high metal ions, infections, pseudotumors, ALVAL and metalosis.
There has been a lot of discussion among patients on discussion groups about the high metal ion issue and pseudotumors. I am not a doctor or medically trained. I am a Patient Advocate, Hip Resurfacing Patient and Mechanical Engineer. I had the opportunity to attend the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA. I listened to discussions about the metal ion issues and pseudotumors. I am going to explain what I learned in simple, non-medical terms since that is all I can do.
As an observer, I learned that the high metal ion issue has occurred in a small number of cases as a post op problem after a hip resurfacing. One of the most likely reasons, according to the experienced surgeons and presenters at the course, was the incorrect placement of the acetabular cup which resulted in additional wear on the bearing surface between the acetabular cup and the femur cap component. The hip resurfacing device is really a metal bearing made of High Carbon Cobalt-Chromium alloys. A bearing is designed to equally spread out the load over the load bearing components. If the components are not aligned properly, then only part of the bearing is loaded resulting in much more wear in that area possibly causing a high metal ion level. It was also explained that women seem to have more problems with high metal ions than men. Perhaps, this is due to the fact that most women use smaller sized hip resurfacing devices which causes more loading on the bearing surfaces than the men’s larger sized devices.
When there is an abnormally high metal ion release from misplaced components, it seems to cause the surrounding tissue and bone to react adversely. The surrounding tissue and bone tends to become abnormal. Some doctors call the tissue reaction pseudotumors, AVAL (aseptic lymphocyte dominated vasculitis associated lesion), & others call it metalosis. Whatever name given to the abnormal reaction, it is not good to have this happening around the hip device since it could become loose, pain could result and possibly more severe medical reactions could happen.
There is concern among the hip resurfacing community about the reactions to the very high metal ion issue. At this time, to my understanding, there is not a standardized blood test available. Different labs use different methods and tests. There are not yet any specific guidelines as to what levels are too high for metal ions. There is a lot of research being done, but there are no standards yet.
This makes a surgeon’s job to define and solve problems due to high metal ions difficult. Some doctors feel that patients with very high metal ions should have a revision of their hip resurfacing to a ceramic on ceramic THR. They don’t want to take chances that even more serious problems could develop due to the high metal ions. Normally, from what I understand, the high metal ions are probably due either to the incorrect position of the acetabular cup causing very high wear on the hip resurfacing bearing device or due to the use of a small hip resurfacing device causing excessive loading on the bearing surfaces. So once again, the learning curve and experience of hip resurfacing surgeons is very important to prospective patients along with proper patient selection. It takes a great deal of experience to consistently place the acetabular cups at the proper angle and to know which smaller patients can successfully receive a hip resurfacing.
That is my layman’s explanation of the high metal ion issue. I am posting a number of abstracts below by surgeons attending the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA. Their articles will help explain more about the high metal ion issue, the small device issue used in many women and the acetabular cup placement issue.
Pathophysiology of Adverse Tissue Reactions to Metal Particles and Ions Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA Joshua J. Jacobs, M.D.Professor and Chairman, Department of Orthopaedic SurgeryRush University Medical CenterChicago, IL
Recently there have been reports that there is a unique histological response in patients with metal on metal bearings in which there is a prominent perivascular and/or diffuse lymphocytic infiltration that is reminiscent of a delayed type hypersensitivity response. This response has been termed ALVAL (aseptic lymphocyte dominated vasculitis associated lesion) and it is reported around metal-on-metal implants from various manufacturers. This issue is not completely understood and the incidence of individuals requiring revision for an apparent hypersensitivity to otherwise well functioning meta lon-metal bearings is currently unknown, but thought to be relatively low. Recent clinical reports have suggested a link between early osteolysis in patients with metal-on-metal bearing total hip replacement systems and metal hypersensitivity, based on either patch testing or histological evidence of so-called ALVAL. In addition, there are reports of pseudotumors occurring in association with metal on metal bearings that may be independent of the ALVAL phenomenon.
Degradation products either in the form of ionic or particulate debris can complex with local proteins, which alters their confirmation and elicits an allergic response comparable with a delayed type hypersensitivity response (Type IV). This type of hypersensitivity is mediated by T lymphocytes reactive against metal ion-modified self-proteins. This provides the primary stimulus to the immune response. To respond with an immune response, the T lymphocyte must also get a secondary stimulus. This is classically provided by co-stimulatory molecules, which are classified to soluble and cell membraneboundco-stimulatory molecules. When the T lymphocyte is responding to both primary and secondary stimulus, it will become sensitized starting antigen-driven clonalproliferation and differentiation. In this paradigm, there is co-operation between innate and adaptive immunity. There is some evidence that patients with metal on metal bearings and/or high serum metal levels elicit more response to metal antigen challenge measured as either patch test sensitivity or lymphocyte proliferation. Thus, while there is an idiosyncratic aspect of the allergic response, there is also a dose response component.
Pseudotumour after Hip Resurfacing Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA David W. Murray, MD, FRCS (Orth)Nuffield Hospital, Department of Orthopaedic Surgery University of Oxford Headington, Oxford OX3 7LD UK
A number of patients who have metal-on-metal resurfacing have various symptoms and a soft-tissue mass which we termed a pseudotumour. We report 20 cases. Each patient underwent plain radiography and in some, CT MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken. All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision. We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.
Patient-Specific Cup Position Technique Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA Michael Antony Tuke Finsbury Orthopaedics Ltd.13 Mole Business Park, Randalls Road Leatherhead, Surrey KT22 7BA UK
Acetabular cup placement has been established by long term wisdom at an abduction angle around 45 degrees and anteversion of around 15 degrees. Achieving this position is not an exact science and falls to most surgeons’ judgment case by case. The result is a very wide ranging variation of position. It has become apparent that large ball Metal on Metal implants are particularly susceptible to high wear if placed too open such that edge load bearing occurs. The reduced dislocation rate demonstrated by large balls may have reduced the sense of importance for careful cup placement…
…In addition to this the design of these cups normally provides for a reduced centre edge angle relative to more established cups that have demonstrated good placement at 45degrees abduction. The effective angle of the critical edge that can cause run away wear can be as much as 18 degrees more open than might be expected if placed at 45 degrees. The cup face and introducer placed at 45 degrees will thus place the cup more “open” than is appreciated by the surgeon…
Abduction Angle and Metal Ion Levels in Resurfacing Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA Graham Isaac, PhD Institute of Medical and Biological Engineering School of Mechanical Engineering University of Leeds Leeds, LS2 9JT, UK
Background: There is continued concern over the long-term effects of wear products following hip replacement using metal-metal bearing surfaces. This study considers the effect of cup abduction angle on metal ion levels in a four-centre study of patients who had received the same surface replacement device.
Methods: Patients with a unilateral, low-profile, low clearance metal-metal resurfacing prosthesis (DePuy ASR™; DePuy; Leeds, UK) were recruited from four centres. Whole blood samples were collected, frozen and analyzed using high resolution ICP-MS. The acetabular lateral opening angle was measured on standard antero-posterior radiographs. Results: Forty-four patient were available for review at 24 month. The median ion levels were 1.49ug/l for both chromium and cobalt. This group comprised 34 males and 10females. There was significant variation in pre-operative levels and in the 38 patients in whom this value was available, the increase metal ion levels after 24 months were0.75ug/l and 0.97ug/l for chromium and cobalt respectively. In 58% of patients the increase in chromium level at 24 months from pre-operative levels was less than 1ug/l(53% for cobalt). However, after 24 months implantation there were 6 outliers with cobalt or chromium levels greater than 10ug/l. Fifty percent of patients with a high lateral opening angle (>55°) had a metal ion level >10ug/l compared to 6% in those withal lower angle (<55°). Two of the four centres had a higher cup abduction angles (53°, 50°compared with 45°, 44°). Four out of the six outliers in this series were implanted at the centre with the highest mean cup abduction angle.
Conclusions: Large diameter metal bearings with low radial clearance can produce very low whole blood metal ion levels. However ion levels, and by inference wear, increase with acetabular lateral opening angle. Furthermore, component mal-position and its effect are not uniformly distributed across the four centres contributing to this study which suggests that the occurrence of high metal ions levels may be avoided by correct component position.
What are the Desired Component Positions for Resurfacing? Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA Justin Peter Cobb, MD5 Devonshire Place London, W1G 6HL UK
Component positioning in each case should be based upon the individual’s pathology. The underlying disease process will determine the pathological positions and angulations that need to be corrected…
… Acetabular component positioning does not pose too many problems for the hip surgeon, save the restricted choice of component size depending on the head size. Femoral component positioning and sizing is the major issue.
Most commonly, this procedure is performed for cam type hips. To optimize the load transfer between head and neck in this condition, the component centre must first be translated anteriorly and superiorly, then angulated into greater valgus and anteversion. The socket should be translated posteriorly, inferiorly and deeper, with angulation optimized depending on gender and morphology…
…Individual cases may need variations at the limits of these parameters. If they cannot be achieved in preoperative planning, then total hip arthroplasty with a less demanding bearing couple may be more appropriate.
Common Femoral Misplacements:
Head in varus: will predispose to fatigue fracture Head inferior on neck: will predispose to neck notching and fracture
Head posterior on neck: will cause impingement in flexion and anterior notching
Head too large, centered on cam: makes the socket too big causing impingement
Head too small: Minimal room for error, neck on socket impingement can occurCommon Acetabular Misplacements:
Socket proud: excessive offset, leading to some pain and stiffness
Socket retroverted: may cause psoas impingement
Socket too anteverted and too steeply inclined: will cause an increased wear rate.
Painful Total Hip Resurfacing Arthroplasty Presented at the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA John Antoniou, MD, PhD, FRCSC Jewish General Hospital3755 Cote-St. Catherine Road Room E-003Montreal, Quebec H3T 1E2 Canada
Evaluation and treatment of the painful total hip resurfacing arthroplasy can be challenging even for the most experienced arthroplasty surgeon. The possibility of metal sensitivity as a cause of persistent groin pain should always be considered in metal on metal resurfacing hip replacements. Additionally, iliopsoas tendinopathy, and anterior impingement of the hip joint are well recognised causes of pain and should be part of the differential diagnosis. Even though the exact clinical significance of the femoral neck narrowing and the incidence of femoral head osteonecrosis are still largely unknown, surgeons should be monitoring the radiographic signs of these entities and consider them as possible causes of pain as well…
A True Personal Story of a Revision of a BHR to THR due to Malpositioning of Device and High Metal Ions.
Received January 9, 2009
Hi Pat,I hope that you are well. I just thought I would email you personally with information for your file and research that has sadly led to me having a revision from BHR to THR. The reason was due to malpositioning of the acetabular cup and femoral component by my surgeon. My surgeon had carried out over 480 hip resurfaces but for some reason a bad day at the office lead to my BHR only lasting 5months. I have attached to x-rays (photos of my x-rays). Sorry for bad quality. I had the anterolateral approach. He has been very supportive to me since the extent of the problem was diagnosed and even encouraged me to have my revision with Doctor De Smet. He has told me I was his first problem with hip resurfacing. I had my revision surgery in Belgium by Doctor De Smet in Dec. He was fantastic and the staff at the Villa were brilliant. It was a very difficult time for me to have my second major surgery in 6 months however Doctor De Smet felt that my original BHR was a disaster (his words) and I was better off not waiting long to have a revision as the steep angle and not being recessed enough was causing muscles and soft tissue damage along with elevated metal ions. Along with the cup malpositioning the femoral head was in an anteverted position causing a tight feeling and making it very difficult to walk straight and without pain. I am 43 and although I tried to avoid a THR with my hip resurfacing last summer I am now the proud owner of a Wright medical Conserve THR with BFH. I am walking without crutches or cane at 6 weeks. I have learned a lot from this experience. Most of all I have learned that I really should have used the most experienced surgeon I could find first time. I have read so much about this on your web site but it is true. This is a complicated operation for any surgeon. If it goes wrong the revision experience is pretty tough. Please keep preaching this message to people contemplating hip resurfacing. Well thanks my story and I thought it might interest you with your research. Best wishes. John ( Revision)