Metal-on-Metal A clinical overview

Transcription

1 Metal-on-Metal A clinical overview

2 Adverse reactions to metal debris In response to the earlier medical device alert published by the MHRA on all metal-on-metal hip replacements, Corin aims to provide clarity and perspective on the many publications that relate to large diameter metal-on-metal articulations. The alert discusses the reports of revisions due to soft tissue reactions which may be associated with unexplained pain. It recommends the follow-up of metal-on-metal hip replacements, including where appropriate blood metal ion measurement and cross-sectional imaging. Over the last three years there has been much debate relating to the subject of adverse reactions to metal-on-metal wear debris (ARMD). This document aims to provide a balanced perspective and summary of the publications both against and in support of hip resurfacing and large diameter metalon-metal articulations. More recently the BOA and the British Hip Society (BHS) have released further details of the results presented at the BHS meeting in Torquay (March, 2011). Several units presented higher than anticipated early failure rates for large diameter metal-on-metal hip resurfacing and replacements. Within these presentations there was a predominance of the ASR XL and ASR resurfacing devices, which have been withdrawn, but they stated that other large diameter metal-on-metal devices may also be showing similar results.

3 Introduction Prior to the development of third generation metal-on-metal articulations, there was no viable long-term, bone conserving solution for challenging, active patients. The addition of this technology revolutionised the treatment of this patient group. Third generation metal-on-metal hip resurfacings and large diameter metal-on-metal total hip replacements (THRs) have been available for over ten years. The published data shows a high survivorship for young, active patients treated with these articulations. A number of series and joint registries show: 94.0% survivorship at 7 years % survivorship at 8 years % survivorship at 10 years 3 Baker et al. have shown after a mean nine year follow-up, patients with a hip resurfacing versus a hybrid total hip replacement have remained more active and have superior function 4. The most prevalent risk of failure in hip resurfacing has previously been identified as femoral neck fracture 5, which tends to be an early failure mode (15 weeks post-operatively) and the risk is greatly reduced by correct patient selection and surgical technique 5,6. As the follow-up period increases for metal-on-metal hip resurfacing, some of the literature points to later complications associated with pain, fluid surrounding the joint (described as large sterile effusion of the hip), microscopic necrosis and metallosis 7. These symptoms are described as adverse reactions to metal debris (ARMD) 7. This review discusses ARMD, the associated risk factors, the impact of implant design and the clinical results of metal-on-metal hip resurfacing and large diameter metal-on-metal total hip replacement.

4 ARMD literature A series of papers have been published from a group of surgeons in Oxford (UK) that discuss the issue of pseudotumours 8,9,10,11,12,13,14. Pandit et al. 8 reported on 17 patients (20 hips) from a cohort of more than 1300 patients (Oxford patients and tertiary referrals) who presented with symptoms termed pseudotumours described as soft tissue masses. The cause of these masses was not clearly determined (a weak correlation between the incidence and cup inclination was noted). However, the group extrapolated their data to predict that approximately 1% of all patients receiving a metalon-metal hip resurfacing would develop a pseudotumour within 5 years and more recently have shown an incidence of 4% at 5 years 14. Although the authors state that pseudotumours have not been observed in conventional total hip replacement, the term in fact dates back to 1987 and has previously been associated with metal-onpolyethylene hips and methylmethacrylate found in bone cement 15. The British Orthopaedic Association (BOA) states that the incidence of ARMD is rare and is somewhere between 1 and 9 per thousand devices implanted 18. In the second paper published by the Oxford group, Grammatopoulos et al. 9 stated that the increased wear responsible for pseudotumours is probably as a result of edge loading or impingement interfering with the lubrication or destroying the congruency of the articulation. In a recent paper they highlight that in order to minimise the risk of pseudotumour formation, it was recommended that surgeons implant the acetabular component at an inclination of 45 (± 10) and anteversion of 20 (± 10). The incidence of pseudotumours inside the optimal zone was four times lower than outside the zone 12. In a further paper Glyn-Jones et al. 10 discussed the risk factors for inflammatory pseudotumour formation following hip resurfacing. This paper, identified the risk of revision associated with pseudotumours as 4% for all patients at 8 years, and 0.5% for men at 8 years.

5 Risk factors for revision Glyn-Jones et al. 10 described the risk factors as female gender, small component size, age and a diagnosis of dysplasia. The incidence of pseudotumours is not associated to implant type according to the authors. The Cormet Hip Resurfacing (Corin), Birmingham Hip Replacement (BHR) (Smith & Nephew), Conserve Plus (Wright Medical) and Recap (Biomet) systems were reviewed. They stated that gender and age have a significant independent effect. The paper concludes that females could be at a higher risk due to the increased prevalence of allergies to jewellery and/or the increased range of motion and therefore increased impingement and wear. A small bearing may also be a contributing factor as the effect of hydrodynamic lubrication may be diminished or the superior cover of the implant reduced. A diagnosis of dysplasia may also increase the risk of misalignment, leading to impingement and wear. The Oxford group advise caution when indicating a resurfacing for a female especially those under 40 years old, however they stated it remains a good option for young men. It has been noted that some patients have presented with an ARMD without component malpositioning 10,17. The wear of metal-on-metal hip resurfacings is multi-factorial and implant position (abduction and anteversion), component size and activity levels may have an effect. In a separate series, Hart et al. discussed a cohort of patients with metalon-metal hip resurfacings revised for unexplained pain. In this series a high proportion of patients revised had a component positioned outside the Lewinnek safe zone 15 (13 out of 16 patients). This paper concluded that the increased incidence of metal debris due to component malpositioning and the risk of impingement due to reduced head-neck ratio are associated with revision of metal-on-metal hip resurfacings. Hart et al. 18 have also presented the threshold for metal sensitivity and specificity of high blood metal ions in predicting failure as 7ppb and recommends monitoring patients with metal ion levels greater than this. Grammatopoulos et al. have also considered the head-neck ratio and found patients in whom pseudotumour formation occurs have a higher pre-operative head-neck ratio than control patients. Therefore at operation the patients with pseudotumours had a greater reduction in the size of their femoral heads and subsequently had greater neck narrowing. They showed that no female patient with a pre-operative HNR 1.3 developed a pseudotumour. They suggest that reducing the size of the femoral head, made possible by a high pre-operative HNR, increases the risk of impingement and edge loading. This may contribute to high wear and pseudotumour formation. This study suggests that it is also reasonable to resurface in women with a preoperative HNR Nargol et al. 7 discussed ARMD and stated that without exception the literature reports an increased incidence of these problems in women. This paper concludes that smaller component size, sub-optimal orientation and component design are factors which make the patients more susceptible to wear and therefore possibly at a higher risk due to the increase in generation of metal debris. They also concluded that females may be at risk due to higher acetabular inclination, anteversion, smaller joint size, increasing the risk of posterior impingement and micro-separation leading to higher wear of the bearing. In addition to female gender, small component size and higher abduction angles, Ollivere et al. 19 report that an additional risk factor for revision due to ARMD is a high BMI leading to difficulty in positioning the cup in the correct orientation. The importance of patient selection was previously highlighted by Stulberg et al. 5 during the Cormet IDE study. Female gender, component size and a lower pre-operative Harris Hip Score were found to be significant risk factors for revision. If the patient indicated had multiple risk factors compared to none or one, the data showed the patient is more likely to require a revision.

6 Implant design It has become evident that in addition to the points noted herein, implant design also plays an important role in the success of hip resurfacing. Nargol et al. 7,20 discussed the impact of a lower subtended angle in the cup design and its effect on the potential for edge loading leading to high wear. The ASR design (DePuy) subtends to an angle of 151 for a 52mm acetabular component 6, whereas Cormet hip resurfacing has an increased arc of coverage of 163 which results in a decreased risk of edge loading and wear. This demonstrates the need for the greater arc of coverage seen in third generation hip resurfacings such as Cormet. In addition, Angadji et al. showed that the metallurgy of the Cormet device may protect the device from excessive wear at high angles 21. Kwon et al. 11 from the Oxford group analysed eight resurfacing components revised for pseudotumours and found they had increased wear and edge loading. They concluded our findings are the first direct evidence that pseudotumours are associated with increased wear at the metal-on-metal articulation. Furthermore, edge loading with the loss of fluid-film lubrication may be an important mechanism for the generation of wear in patients with a pseudotumour. This further supports the importance of arc of coverage in resurfacing and large diameter metal-on-metal components. Langton et al. looked at three implant designs, the Articular Surface Replacement (ASR), the Birmingham Hip Resurfacing (BHR) and the Conserve Plus. The survival analysis showed a failure rate in the patients with ASR of 9.8% at five years, compared with <1% at five years for the Conserve Plus and 1.5% at ten years for the BHR. Increased wear from the metal-onmetal bearing surface was associated with an increased rate of failure secondary to ARMD 18. The Cormet cementless resurfacing shows a 95% survivorship at four to five years 22. Large diameter metal-on-metal hip replacements Most recently, discussions have concerned the survival of large diameter metal-on-metal hip replacements. At the British Hip Society (BHS) meeting in March 2011, several groups presented higher than anticipated early failure rates for large diameter metal-on-metal hip replacements. The ASR XL device shows a revision rate of 21% at 4 years, potentially rising to 35% if all currently known painful implants progress to revision and up to 49% at 6 years. The BHS stated that other devices have a revision or impending revision rate of %. Bolland et al. reported the mid-term results of a large diameter BHR (Smith and Nephew) metal-on-metal total hip replacement with a CLS stem (Zimmer) in 199 hips (185 patients) with a mean follow-up period of 62 months. 17 hips (8.5%) underwent revision and a further 14 were awaiting surgery. All revisions were symptomatic. Of the revision cases, 14 hips showed evidence of adverse reactions to metal debris. The patients revised or awaiting revision had significantly higher whole blood cobalt ion levels but no significant difference in acetabular component size or position compared with the unrevised patients. The paper also discussed wear analysis which showed increased wear at the trunnion-head interface, normal levels of wear at the articulating surfaces and evidence of corrosion on the surface of the stem. The cumulative survival rate, with revision for any reason, was 92.4% at five years. Including those awaiting surgery, the revision rate would be 15.1% with a cumulative survival at five years of 89.6%.This metal-onmetal total hip replacement has shown evidence of high wear at the trunnion-head interface and passive corrosion of the stem surface. This paper raises concerns about the use of large heads on conventional 12/14 tapers 23. The NJR data for Corin s Optimom large diameter metal-on-metal hip replacement shows a revision rate of 4.6% at 4 years in 1080 patients according to the NJR data 24.

7 Cormet clinical results Data has been collected on two large cohorts of patients who have received a Cormet hip resurfacing. These cohorts are multi-centre studies and show a very small number of ARMD cases. In the first cohort, 4 of 1743 hips (0.22%) were revised due to metallosis or ALVAL 25. In this group of 1515 patients, the average age was 54 years (20-89 years) and the majority had a pre-operative diagnosis of osteoarthritis (92%) with the remainder made up of a variety of AVN, inflammatory arthropathies and post-traumatic cases. The cohort consisted of 921 males and 594 females. In the second cohort, the patients had a Cormet hip resurfacing implanted under an FDA approved investigational device exemption (IDE) study and there is 1 reported ARMD case (0.08%) from 1183 patients 26. From the second cohort, Gross et al. 27 presented at the American Academy of Orthopaedic Surgeons (AAOS) meeting in 2010, the results of the Cormet hip resurfacing in 329 patients (373 hips) showed a survivorship of 94.4% at 8 years with one revision (0.3%) revisions due to ARMD. although pseudotumors remain a concern after metal-on-metal hip resurfacing the prevalence at short to mid-term follow-up is very low in this multicentre survey. Ho et al. performed a radiographic review of a consecutive series of 87 Cormet resurfacing arthroplasties to review neck narrowing. There were 54 cemented femoral components and 33 uncemented femoral components. All of the procedures were performed by the same surgeon using the same approach. The primary outcome measured was the neck-prosthesis ratio on standard anterior-posterior pelvis radiographs taken post-operatively and at a minimum follow-up of two years. The difference between the immediate post-operative ratio and the most recent radiograph was statistically significant in patients with cemented femoral components but not in the group with uncemented components. This demonstrates a difference in narrowing of the femoral neck between cemented and uncemented femoral components in the first two years following surgery and may be predictive of the improved results seen with the fully cementless resurfacing system 29. Furthermore Spencer et al. reports on the results of a multicentre evaluation of procedures done with the Cormet cementless system, performed by six surgeons in different centres in the United Kingdom. The results show 95% survivorship at four to five years in 178 patients 22. Beaule et al. 28 reported on 3432 hip resurfacing arthroplasties (Cormet, BHR, Durom, ASR, Conserve Plus and Mitch) from nine centres with a mean follow-up of 3.4 years that pseudotumors developed in four patients. Resulting in a prevalence of 0.10%. They concluded that

8 Over 20 years expertise in metal-on-metal hip resurfacing 1989 Vision Origin 1997 Evolution 2004 Innovation Corin begins development of the first metal-on-metal hip resurfacing The first implantation of the Corin McMinn Hip Resurfacing Corin Cormet Hip Resurfacing is launched First fully cementless resurfacing becomes available, removing all cement from the procedure

9 Conclusion The literature concludes that a number of factors influence the success of metal-on-metal hip resurfacings and THRs. It is important that the following are considered when selecting and implanting Cormet hip resurfacing or an Optimom large diameter metal head with a Cormet resurfacing acetabular component. In conclusion, Corin believes metal-on-metal hip resurfacing remains a safe and effective surgical intervention for well-indicated patients and Cormet continues to form an important part of our continuum of care in hip replacements. Patient selection: do not implant in contra-indicated patients such as women of child bearing age as stated in the instructions for use (IFU) document. When indicating a patient, consideration should be given to the bone quality, component size and diagnosis of the patient. Component positioning: ensure the acetabular components are implanted with a maximum inclination of 45 and of anteversion to minimise the potential of edge loading leading to increased metal wear debris Expansion Cormet is launched in the USA by Stryker Orthopaedics 2008 Progression 2mm incremental heads become available, allowing greater intra-operative flexibility 2011 Celebration Corin celebrates 20 years of metal-on-metal hip resurfacing, with over 40,000 implantations worldwide during this period

10 Hip continuum of care Advanced bearing technologies BIOLOX delta and ECiMa

11 References 1. Steffen RT, Pandit HP, Palan J, Beard DJ, Gundle R, McLardy-Smith P, Murray DW, Gill HS. The five-year results of the Birmingham Hip Resurfacing arthroplasty: An Independent Series. J Bone Joint Surg [Br] Apr;90(4): Khan M, Kuiper JH, Edwards D, Robinson E, Richardson J. Birmingham Hip Arthroplasty: Five to eight years of prospective multicenter results. J Arthroplasty Oct; 24(7): Treacy RB, McBryde CW, Shears E, Pynsent PB. Birmingham hip resurfacing: a minimum follow-up of ten years. J Bone Joint Surg [Br] Jan;93(1): Baker RP, Pollard TC, Eastaugh-Waring SJ, Bannister GC. A medium-term comparison of hybrid hip replacement and Birmingham hip resurfacing in active young patients. J Bone Joint Surg [Br] Feb;93(2): Stulberg BN, Trier KK, Naughton M, Zadzilka JD. Results and lessons learned from a United States hip resurfacing investigational device exemption trial. J Bone Joint Surg [Am] Aug;90(suppl 3): Shimmin AJ, Back D. Femoral neck fractures following Birmingham hip resurfacing: a national review of 50 cases. J Bone Joint Surg [Br] Apr;87(4): Langton DJ, Jameson SS, Joyce TJ, Hallab NJ, Natu S, Nargol AV. 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] Jan;92(1): Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gibbons CL, Ostlere S, Athanasou N, Gill HS, Murray DW. Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg [Br] Jul;90(7): Grammatopolous G, Pandit H, Kwon YM, Gundle R, McLardy-Smith P, Beard DJ, Murray DW, Gill HS. Hip resurfacings revised for inflammatory pseudotumour have a poor outcome. J Bone Joint Surg [Br] Aug;91(8): Glyn-Jones S, Pandit H, Kwon YM, Doll H, Gill HS, Murray DW. Risk factors for inflammatory pseudotumour formation following hip resurfacing. J Bone Joint Surg [Br] Dec;91(12): Kwon YM, Glyn-Jones S, Simpson DJ, Kamali A, McLardy-Smith P, Gill HS, and Murray DW. Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours. J Bone Joint Surg [Br]. 2010;92-B: Grammatopoulos G, Pandit H, Glyn-Jones S, McLardy-Smith P, Gundle R, Whitwell D, Gill HS, Murray DW. Optimal acetabular orientation for hip resurfacing.j Bone Joint Surg [Br] Aug;92(8): Grammatopoulos G, Pandit H; Oxford Hip and Knee Group, Murray DW, Gill HS. The relationship between head-neck ratio and pseudotumour formation in metal-on-metal resurfacing arthroplasty of the hip. J Bone Joint Surg [Br] Nov;92(11): Kwon YM, Ostlere SJ, McLardy-Smith P, Athanasou NA, Gill HS, Murray DW. Asymptomatic Pseudotumors After Metal-on-Metal Hip Resurfacing Arthroplasty Prevalence and Metal Ion Study. J Arthroplasty Jun;26(4): Epub 2010 Jun Griffiths HJ, Burke J, Bonfiglio TA. Granulomatous pseudotumors in total joint replacement. Skeletal Radiol. 1987;16(2): BOA Metal on Metal Guidance Hart AJ, Sabah S, Henckel J, Lewis A, Cobb J, Sampson B, Mitchell A, Skinner JA. The painful metal-on-metal hip resurfacing. J Bone Joint Surg [Br] Jun;91(6): Hart AJ, Bandi A, Sabah S, et. al. High blood cobalt levels can be used to predict failure of metal on metal (MOM) hips. Paper #7. Presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons. March New Orleans. 19. Ollivere B, Darrah C, Barker T, Nolan J, Porteous MJ. Early clinical failure of the Birmingham metal-on-metal hip resurfacing is associated with metallosis and soft-tissue necrosis. J Bone Joint Surg [Br] Aug;91(8): D. J. Langton, T. J. Joyce, S. S. Jameson, J. Lord, M. Van Orsouw, J. P. Holland, A. V. F. Nargol, and K. A. De Smet Adverse reaction to metal debris following hip resurfacing: The Influence Of Component Type, Orientation And Volumetric Wear. J Bone Joint Surg [Br]. Feb 2011; 93-B: Angadji A, Royle M, Collins SN, Shelton JC. A hip simulator study on the effect of cup inclination on the wear of as cast and double heat-treated metal-on-metal hip replacements. ORS March 2007:Poster. 22. Robert Spencer. Evolution in Hip Resurfacing Design and Contemporary Experience with an Uncemented Device. J Bone Joint Surg [Am]. 2011;93(Supplement 2): Bolland BJ, Culliford DJ, Langton DJ, Millington JP, Arden NK, Latham JM. High failure rates with a large-diameter hybrid metal-on-metal total hip replacement: Clinical, Radiological And Retrieval Analysis.J Bone Joint Surg [Br] May;93(5): Data held on file at Corin Group 25. Unitt L, Bracey D, Fern D, Foguet P, Krikler S, Norton M, Prakash U, Pring D, Spencer R, Vhadra R, Bishay M. The intermediate results of a multi-surgeon, multi-centre cohort using the Cormet hip resurfacing device. BOA 2009:Poster. 26. Data held on file at Corin USA. 27. Gross TP, Liu F. Eight year clinic outcomes of the metal-on-metal hybrid hip surface replacement. AAOS 2010:Podium presentation, paper Paul E. Beaulé and the Canadian Hip Resurfacing Study Group A Survey on the Prevalence of Pseudotumors with Metal-on-Metal Hip Resurfacing in Canadian Academic Centers J Bone Joint Surg [Am]. 2011;93(Supplement 2): Ho KK, Beazley J, Parsons N, Costa ML, Foguet P.Narrowing of the femoral neck after resurfacing arthroplasty of the hip: a comparison of cemented and uncemented femoral components. Hip Int Oct-Dec;20(4):542-6.

12 The Corinium Centre, Cirencester, GL7 1YJ t: +44(0) f: +44(0) e: Printed on 9lives 80 which contains 80% total recycled fibre and is produced at a mill which holds the ISO for Environmental Management Systems. The pulp is bleached using Elemental Chlorine Free processes Corin P No I1040 Rev1 05/2011 ECR 11054