title: Explant analysis of the Biomet Magnum/ReCap metal-on-metal hip joint.
abstract: OBJECTIVE
  The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces.
  
  
  METHODS
  In this study, a coordinate measuring machine (CMM) was used to measure the wear on five failed cementless Biomet Magnum/ReCap/ Taperloc large head MoM THAs, along with one Biomet ReCap resurfacing joint. Surface roughness measurements were also taken. The reason for revision of these implants was pain and/or adverse reaction to metal debris (ARMD) and/or elevated blood metal ion levels.
  
  
  RESULTS
  The mean wear rate of the articulating surfaces of the heads and acetabular components of all six joints tested was found to be 6.1 mm3/year (4.1 to 7.6). The mean wear rate of the femoral head tapers of the five THAs was 0.054 mm3/year (0.021 to 0.128) with a mean maximum wear depth of 5.7 µm (4.3 to 8.5).
  
  
  CONCLUSIONS
  Although the taper wear was relatively low, the wear from the articulating surfaces was sufficient to provide concern and was potentially large enough to have been the cause of failure of these joints. The authors believe that patients implanted with the ReCap system, whether the resurfacing prosthesis or the THA, should be closely monitored.Cite this article:S. C. Scholes, B. J. Hunt, V. M. Richardson, D. J. Langton, E. Smith, T. J. Joyce. Explant analysis of the Biomet Magnum/ReCap metal-on-metal hip joint.Bone Joint Res2017;6:113-122. DOI: 10.1302/2046-3758.62.BJR-2016-0130.R2.
authors.affiliation: School of Mechanical and Systems Engineering, Newcastle University, Claremont Road, Newcastle-upon-Tyne, NE1 7RU, UK susan.scholes@ncl.ac.uk.
authors.forename: S C
authors.initials: SC
authors.lastname: Scholes
authors.affiliation: School of Mechanical and Systems Engineering, Newcastle University, Claremont Road, Newcastle-upon-Tyne, NE1 7RU, UK.
authors.forename: B J
authors.initials: BJ
authors.lastname: Hunt
authors.affiliation: School of Mechanical and Systems Engineering, Newcastle University, Claremont Road, Newcastle-upon-Tyne, NE1 7RU, UK.
authors.forename: V M
authors.initials: VM
authors.lastname: Richardson
authors.affiliation: Freeman Hospital, Newcastle-upon-Tyne, NE7 7DN, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Langton
authors.affiliation: Avon Orthopaedic Centre, North Bristol NHS Trust, Southmead Hospital, Westbury-on-Trym, Bristol, BS10 5NB, UK.
authors.forename: E
authors.initials: E
authors.lastname: Smith
authors.affiliation: School of Mechanical and Systems Engineering, Newcastle University, Claremont Road, Newcastle-upon-Tyne, NE1 7RU, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: Joyce
keywords: Arthroplasty; Film Thickness; Hip; Lubrication; Metal-on-Metal; Taper; Wear