Lessons from retrievals: Retrievals help understand the reason for revision of coated hip arthroplasties.
Coatings have been applied to all surfaces of hip implants with the majority performing well in the laboratory, but there are few reports of their performance in humans. The rationale for coating the metal-on-metal bearing surfaces includes a reduction in metal ion release and risk of adverse reaction to metal debris; yet there are no reports of retrieved coated metal-on-metal hip implants despite the concern that they may delaminate. The aim of this study was to better understand the performance of coated hip implants in humans through findings of three coated metal-on-metal hip resurfacings, retrieved after failure for unexplained pain. Analysis of these implants included quantification of the amount and mechanism of coating loss which was correlated with clinical, imaging and blood data. In all cases, there were large areas of complete coating loss in which the metal substrate was exposed and found to be rougher than the coated areas. The coating loss gave rise to third body abrasive wear of the coating and the exposed metal, the latter of which led to high blood levels of cobalt and chromium. Coating of the bearing surfaces of metal-on-metal hip resurfacings, therefore, do not prevent metal ion release when implanted into humans. This is an example of a need for increased retrieval analysis of newly introduced implants and expansion of laboratory testing regulations to better reflect the clinical environment.
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK d.de-villiers@ucl.ac.uk.
Danielle
D
de Villiers
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Harry
H
Hothi
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Harman
H
Khatkar
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Jayantilal
J
Meswania
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Gordon
G
Blunn
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
John
J
Skinner
Institute of Orthopaedics and Musculoskeletal Science, University College London, Royal National Orthopaedic Hospital, Stanmore, UK.
Alister
A
Hart
D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation; D001696:Biomechanical Phenomena; D020099:Coated Materials, Biocompatible / Q000009:adverse effects*; D019544:Equipment Failure Analysis; D017276:Friction; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D009556:Niobium; D011475:Prosthesis Failure; D012086:Reoperation; D014025:Titanium
D020099:Coated Materials, Biocompatible; D009556:Niobium; C041500:titanium nitride; D014025:Titanium
Wear analysis or testing (biomechanics); implants or prosthetics; orthopaedic materials; orthopaedic tribology; tribology of coatings; tribology of materials; wear modes