Metallosis Following Bipolar Hemiarthroplasty Due to Polyethylene Wear: A Case Report

Metallosis following bipolar hemiarthroplasty is an uncommon complication that can result from wear of the concealed polyethylene bearing within the bipolar head.We report the case of a 54-year-old man who presented with six months of progressive right hip pain, four years after bipolar hemiarthroplasty for a transcervical fracture of the femoral neck.Laboratory investigations showed no evidence of infection.Radiographs and computed tomography demonstrated eccentric positioning of the femoral head within the bipolar cup, with peri-trochanteric and acetabular osteolysis and a contained supra-acetabular bone defect measuring approximately 2 × 2 cm.During revision surgery, extensive blackish discoloration of the periprosthetic tissues consistent with metallosis was observed.Examination of the retrieved bipolar head demonstrated complete wear-through of the inner polyethylene liner, resulting in direct metal-on-metal articulation between the inner and outer metal components and generation of substantial metallic debris.A two-stage revision was performed.Extended trochanteric osteotomy was required for femoral stem extraction, followed by extensive debridement and placement of an antibiotic cement spacer.After eight weeks, iliac crest bone grafting was performed for the acetabular defect and the patient underwent conversion to cementless total hip arthroplasty.Histopathological examination confirmed metallosis.At follow-up, the patient was pain-free and independently mobile.This case highlights that concealed polyethylene wear within a bipolar head can progress to direct metal-on-metal articulation, metallosis, osteolysis, and prosthetic failure.Eccentric positioning of the femoral head in a painful bipolar hemiarthroplasty should prompt careful evaluation for polyethylene bearing failure, even when inflammatory markers are normal.Early recognition and appropriate staged revision can facilitate management of extensive metallosis and bone loss.