Abstract
BackgroundAdverse Reaction to Metal Debris (ARMD) is still a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. ARMD consists of a wide range of alterations in periprosthetic tissues, most important of which are metallosis, inflammation, pseudotumors and necrosis. Studies investigating histopathological findings and their association to implant wear or indirect measures of wear have yielded inconsistent results. Therefore, we aimed to investigate bearing surface wear volume, whole blood and synovial fluid metal ion concentrations, histopathological findings in periprosthetic tissues and their associations.MethodsSeventy-eight patients with 85 hips revised for ARMD were included in the study. Prior to revision surgery, all patients had whole blood chromium and cobalt ion levels assessed. In revision surgery, a synovial fluid sample was taken and analyzed for chromium and cobalt. Periprosthetic tissue samples were taken and analyzed for histopathological findings. Explanted implants were analyzed for bearing wear volume of both acetabular cup and femoral head components.ResultsVolumetric wear of the failed components was highly variable. The total wear volume of the head and cup had a strong correlation with whole blood chromium and cobalt ion concentrations (Cr: ρ = 0.80, p < 0.001 and Co: ρ = 0.84, p < 0.001) and a bit weaker correlation with fluid chromium and cobalt ion concentrations (Cr: ρ = 0.50, p < 0.01 and Co: ρ = 0.41, p = 0.027). Most tissues displayed only low-to-moderate amounts of macrophages and lymphocytes. Total wear volume correlated with macrophage sheet thickness (ρ = 0.25, p = 0.020) and necrosis (ρ = 0.35, p < 0.01). Whole blood chromium and cobalt ion concentrations had similar correlations. Lymphocyte cuff thickness did not correlate with either total wear volume or whole blood metal ion concentrations, but correlated with the grade of necrosis.ConclusionsBearing wear volume correlated with blood metal ion levels and the degree of necrosis and macrophage infiltration in periprosthetic tissues suggesting a dose-response relationship. Whole blood metal ion levels are a useful tool for clinician to estimate bearing wear and subsequent tissue response.
Highlights
Adverse Reaction to Metal Debris (ARMD) is still a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements
All consecutively revised patients who gave informed consent and fulfilled the following criteria were included in our study: 1) Revision was due to ARMD, 2) Retrieved components were available for bearing wear analysis and 3) Periprosthetic tissue sample was available for histopathologic analysis
Total wear volume correlated with macrophage sheet thickness, grade of necrosis (Fig. 3), synovial lining score, tissue organization score and total Aseptic lymphocytic vasculitis-associated lesion (ALVAL) score
Summary
Adverse Reaction to Metal Debris (ARMD) is still a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. Retrieval studies have investigated implant wear and its association to ARMD Results of these studies have been inconclusive as adverse reactions have been observed both in patients with high and low wearing hip implants [5,6,7,8,9,10,11]. In their recent systematic review, Campbell et al concluded that no clear dose-response relationship between wear and ARMD could be established due to the heterogeneity of the findings in the included studies. Metal hypersensitivity to implant-derived debris has been hypothesized as a cause of ARMD in patients with low-wearing hip implants, and cytotoxic, macrophage dominated response in patients with high-wearing hip implants [8, 13, 16, 17] findings not supporting these hypotheses have been published as well [10, 12, 15, 18, 19]
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