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Long‐term follow‐up of metal‐on‐metal total hip replacement

Metal‐on‐metal articulations were reintroduced to reduce polyethylene particle‐induced osteolysis. Elevated serum metal levels have been detected at short‐ and intermediate‐term follow‐up. There is little knowledge about long‐term effects of increased ionic metal generation. Our study was undertaken to provide information about long‐term survival, clinical outcome, radiographic appearance, and serum metal concentrations after a minimum 10 years follow‐up with a metal‐on‐metal hip prosthesis: 105 cementless primary total hip prostheses with metal‐on‐metal articulating surfaces were implanted in 98 patients with a mean age of 56 years. Clinical data, radiographs, and blood samples were obtained at a follow‐up visit 10 years after implantation. Serum cobalt and chromium levels were determined with use of atomic absorption spectrometry. General laboratory analyses included a full blood count and kidney function parameters. The Harris score was 92 points and the UCLA score 6 points after 10 years. Small osteolytic lesions and radiolucent lines were found in Gruen's zones 1, 7, 8, and 14. The probability of survival was 98.6%. The median serum cobalt concentration of the 22 patients with their hip replacement as the only source of cobalt was 0.75 µg/L (range, 0.3–50.1 µg/L). No patient was diagnosed with renal insufficiency during the study period. Five patients were diagnosed with a malignancy between surgery and the follow‐up. We do not have evidence of an increased rate of primary malignancies nor could we detect renal failure in our study group. Serum metal levels did not differ from short‐ and intermediate term follow‐up values. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:841–848, 2007