Reply to Letter to the Editor: The Withdrawn ASR™ THA and Hip Resurfacing Systems: How Have Our Patients Fared Over 1 to 6 Years?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: 2.77). 08/2012; 471(2). DOI: 10.1007/s11999-012-2547-5
Source: PubMed


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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    Clinical Orthopaedics and Related Research 10/2012; 471(1). DOI:10.1007/s11999-012-2672-1 · 2.77 Impact Factor
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    ABSTRACT: The articular surface replacement (ASR) hip resurfacing system, now withdrawn, has the highest all-cause revision rate (24.2 % at 7 years) compared with other resurfacing brands. We present our experience with the ASR articulation and the implant recall process. We reviewed the medical records and examined all 55 patients (57 hips) who had THA by the senior author between March 2005 and November 2008. We recorded the Oxford Hip scores, metal ion levels, need for revision, the indication for revision, and the intra-operative findings. Radiographs were performed at the time of recall to detect component failure. Survival at 5 years with revision for any reason as the endpoint was 85.1 % for all patients. At the time of recall, 10 (17.5 %) of fifty-seven THAs were already revised. Four (40 %) of the ten revisions were performed within 1 month of the operation due to a periprosthetic fracture. Three other revisions were due to avascular necrosis at a mean time of 3.6 years. One patient was revised due to infection. The two remaining revisions were due to ongoing groin pain, in one of whom the cup was found to be loose. Our data indicate an overall high revision rate, comparable with recently published studies. Even though most of our revisions were attributed to causes that are not specific to the metal-on-metal articulation, we do expect to find more cases of failures in the future. Therefore, continued close clinical surveillance and laboratory monitoring of these patients is warranted.
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    ABSTRACT: Follow-up of pseudotumors observed with metal-artefact reducing sequence (MARS)-magnetic resonance imaging (MRI) following metal-on-metal total hip arthroplasty (MoMTHA) depends on how severe these pseudotumors are graded. Several pseudotumor grading systems for MARS-MRI have emerged but little is known of their validity. We studied the intra- and interobserver reliability of three different pseudotumor grading systems in a single cohort of MoMTHA. Two experienced musculoskeletal radiologists independently used three different pseudotumor grading systems for classifying MARS-MRI results of the same cohort of 42 MoMTHA patients (49 hips, mean follow-up 5.2 years). Intraobserver and interobserver reliability for each grading system was measured using Cohen's kappa (κ). Variance in pseudotumor severity grading between systems was analyzed. Intraobserver reliability on grading pseudotumor severity with the Anderson, Matthies, and Hauptfleisch grading system scored 0.47, 0.10, and 0.35 (observer 1), and 0.75, 0.38, and 0.42 (observer 2), respectively. Interobserver reliability scores for pseudotumor severity were 0.58, 0.23, and 0.34, respectively. Intraobserver reliability for grading pseudotumor severity on MARS-MRI ranged from poor to good, dependent on observer and grading system used. Interobserver reliability scored best with the Anderson system. A more succinct pseudotumor severity grading system is needed for clinical use.
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