Histologic, Serologic, and Tribologic Findings in Failed Metal-on-Metal Total Hip Arthroplasty

Despite multiple changes in second-generation metal-on-metal hip implants, greater-than-expected revision rates have led to alarm. We hypothesized that the finding of intraoperative metallosis would be associated with a high metal load on histologic analysis and that both would be associated with increased wear, greater serum metal ion levels, and predictable biologic responses in the histologic sections. We evaluated the implant positioning, serum ion levels, intraoperative findings of metallosis, wear characteristics of retrieved implants (tribology), histology, and outcomes in a series of eighteen large-diameter metal-on-metal total hip arthroplasties. The arthroplasties were divided into two groups on the basis of the intraoperative finding of metallosis and into two groups on the basis of the metal load score. Intraoperative metallosis was not associated with a high metal load score (p = 0.15). The finding of intraoperative metallosis was associated with greater serum metal ion levels, greater wear rates, and greater complication rates. Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) scores were similar between the metallosis and non-metallosis groups (p = 0.49) as well as between the high and low-metal-load groups (p = 0.56).