Fatigue Failure of Outer Metal Dome of Bipolar Monoblock Shell in Hemiarthroplasty Hip: Case Report and Review of Literature

INTRODUCTION: We report a rare case of transmural wear-through of the polyethylene inner liner leading to fatigue failure of polished outer metallic dome of bipolar monoblock shell in cemented hemiarthroplasty 5-years after the index surgery. CASE PRESENTATION: A 62-year-old active man reported with 6 months of worsening right hip pain. He had undergone cemented bipolar hemiarthroplasty for sub-capital fracture of the right femur 5 years back. Radiographs demonstrate significant full-thickness wear-through of the Cobalt-Chromium head through the polyethylene inner liner and outer metal dome into the acetabulum. Biomechanics study revealed inadequate thickness of outer metallic dome of monoblock shell. Revision Total hip arthroplasty was performed. At the 5-year follow-up, radiographs show stable components and no clinical abnormality. CONCLUSION: Albeit rare, this failure mode aimed to raised awareness, routine follow-up, and quality assurance.