Trunnion Corrosion causing Failure in Metal-on-Polyethylene Total Hip Arthroplasty with Monolithic Femoral Components

We describe nine patients who had total hip arthroplasty failure [titanium alloy monolithic stem, cobalt-chromium head (32 mm or 36 mm), highly cross-linked polyethylene liner, metal socket] related to metal wear debris generated at the trunnion.  Symptoms included pain with onset 2.9 years after THA.   Preoperative serum cobalt metal ion levels were elevated [mean 8.8 ng/ml (normal < 0.9 ng/ml)] and were higher than chromium levels [mean 1.2 ng/ml (normal < 0.3 ng/ml)]. All patients had debridement of the periarticular soft tissues, stem retention, revision to ceramic head and new liner; two patients had acetabular revision.   At early follow-up, 7 of 8 available patients did well, with improved cobalt (0.6 ng/ml) and little change in chromium levels.   We recommend heightened awareness regarding this mode of failure.