Corrosion and adverse tissue reaction after modular unipolar hip hemiarthroplasty

Modern unipolar hip hemiarthroplasty, commonly used for displaced femoral neck fracture, is now modular, with both a variable length cobalt-chromium adapter-sleeve and large femoral head. Patients with these modular components may develop symptomatic trunnion corrosion, with elevated serum metal levels. We report the case of an 82-year-old woman, 5.5 years after a modular unipolar hip hemiarthroplasty, who presented with a 4-month history of hip pain and limp. Evaluation showed elevated serum cobalt and chromium levels and an acetabular cyst. At revision, fluid, tissue, and gross inspection were consistent with trunnion corrosion. The hip was revised with a ceramic head and dual mobility acetabular component, with a good result at 1 year. The designs of commercially available, modern unipolar hip hemiarthroplasty prostheses are reviewed.