Article

Reply to Letter to the Editor: The Withdrawn ASR™ THA and Hip Resurfacing Systems: How Have Our Patients Fared Over 1 to 6 Years?

Department of Orthopaedic Surgery, Duke University Medical Center, Box 3269, Durham, NC, 27710, USA, .
Clinical Orthopaedics and Related Research (Impact Factor: 2.88). 08/2012; 471(2). DOI: 10.1007/s11999-012-2547-5
Source: PubMed

ABSTRACT BACKGROUND: The Articular Surface Replacement™ (ASR™) metal-on-metal hip arthroplasty system (DePuy Orthopaedics, Inc, Warsaw, IN, USA) reportedly has a higher than anticipated early failure rate leading to a voluntary recall. This prompted us to evaluate all ASR™ components implanted at our center. QUESTIONS/PURPOSES: In all ASR™ components, we reported (1) revision rate, (2) blood metal ion levels, and (3) intraoperative findings for revisions related to adverse reaction to metal debris (ARMD). METHODS: We retrospectively reviewed all 172 patients (190 hips) who underwent THA (149 hips) or hip resurfacing (41 hips) with the ASR™ system. We determined failure rates. We obtained blood metal ion concentrations from 93 patients at last followup. We evaluated MRI studies and intraoperative histopathology. Minimum followup was 12 months (mean, 40 months; range, 12-74 months). RESULTS: At latest followup, we had revised 24 of 190 hips (13%): in 18 patients with THA and five patients with resurfacing. Mean time to revision was 45 months (range, 12-75 months). Mean blood concentrations were 13 μg/L (range, 0-150 μg/L) for cobalt and 6 μg/L (range, 0-87 μg/L) for chromium. Mean prerevision blood metal ion levels were higher in the revised group (cobalt: 48 μg/L; chromium: 18 μg/L) than in the nonrevised group (cobalt: 5 μg/L; chromium: 2 μg/L). ARMD was present in 14 of the 24 hips revised in this study. CONCLUSIONS: Surgeons must have a low threshold for concern for ARMD in patients with ASR™ systems. Blood metal ion levels and MRI can be used to evaluate patients with underperforming implants. Intraoperative histopathologic analysis and joint fluid cytology can help diagnose ARMD at the time of revision. LEVEL OF EVIDENCE: Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

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    ABSTRACT: Total hip arthroplasty (THA) is the gold standard in the treatment of degenerative hip disease, especially in the older patient. Concerns regarding the higher levels of failure of traditional implants in younger, more active patients have led to a search for alternative arthroplasty techniques. Hip resurfacing (HR) is one of these alternatives. When compared with THA, HR has some theoretical advantages that stem from preservation of the patient’s normal proximal femoral anatomy and the use of a large diameter metal on metal bearing. This has the potential to more accurately replicate physiological hip function, reduce the risk of dislocation and allow higher levels of activity with minimal wear of the articulating surface. In addition, the preservation of proximal femoral bone stock offers the potential for easier revision options as would inevitably be required in younger patients. In order to be considered a suitable alternative, HR would need to demonstrate improvements or at least equivalence in functional outcomes and survivorship along with evidence of successful preservation of bone stock leading to good outcomes from future revision surgery. Whilst the recent expansion of data both in the orthopaedic literature and the mainstream media concerning the potentially devastating problems from large metal-on-metal (MoM) bearings in some settings carries some salient lessons for both the development, marketing and uptake of new orthopaedic implants, it should be put in the context of the resurfacing literature as a whole. In this review we aim to review the current evidence base for HR compared with THA and examine the current indications for the procedure.