Cobalt-Alloy Metal Debris in Periarticular Tissues From Total Hip Revision Arthroplasties

Abstract

To investigate the hypothesis that an association exists between the presence of metallic particulate or ionic debris released from the components of a total hip replacement and the histologic reaction in the surrounding tissues, cobalt, chromium, nickel, and molybdenum levels were measured in periarticular tissue from 22 individuals who had revision surgery. Total tissue content of the four elements (averaged per case) ranged from 2.7 to 250 µg of metal per gr of dried tissue (mean, 39 µg/gr); however, within each case, the tissue-metal content varied more widely. The highest total tissue-metal contents occurred in cases revised for infection. Fibrosis, histiocytic reaction, hemorrhage, and necrosis were the most frequent histologic findings. Polyethylene and cement particles each appeared in approximately half of all sections, while microscopic metal particles were seen only in tissues from the infected hips. Tissue-metal content did not correlate with the histologic findings, with any of the demographic variables, nor with duration of implantation. Ratios of the individual constituent elements generally reflected the cobalt-chromium alloy composition, suggesting that metal debris was present predominantly as wear particles. Only for tissues with very low metal contents did departures of these ratios indicate the presence of ionic corrosion products. The extremely low metal contents measured in many cement-bone interfacial tissues and the few metal particles found histologically suggest that metal particles may have been less important in inflammatory reaction and loosening than cement or polyethylene particles. The lack of correlation between average tissue-metal contents or histologic findings with duration of implantation, coupled with the wide range of tissue-metal contents observed, suggest that much of the debris may have been generated during that short period of time after significant loosening had occurred.