Aseptic Loosening of Bipolar Hemiarthroplasty in a Young Adult Managed by Conversion to Dual Mobility Total Hip Arthroplasty Complicated by Early Dislocation and Subsequent Infection

ABSTRACT: Conversion of a failed bipolar hemiarthroplasty to total hip replacement (THR) is technically demanding because of acetabular erosion, scarred soft tissues, compromised bone stock and instability risk. Superadded culture-positive infection further complicates implant selection, antibiotic strategy and follow-up surveillance. A 35-year-old male with previous tuberculous meningitis and bilateral avascular necrosis underwent right bipolar hemiarthroplasty in 2016 and left THR in 2019. He later presented with persistent right hip pain and restricted movement. He underwent conversion of the failed right bipolar hemiarthroplasty to THR. Early recurrent instability required a second revision using a long uncemented revision stem, cerclage fixation for an intraoperative proximal femoral fracture and a dual mobility construct. During the infection/revision course, intraoperative culture was positive for Klebsiella pneumoniae. The patient received 6 weeks of intravenous ceftazidime-avibactam and aztreonam. Serial CRP/high-sensitivity c-reactive protein values were 2.92, 239.79, 150.25, 379.13 and 24.43 mg/L, while erythrocyte sedimentation rate values were 6, 103, 103, 75, and 22 mm/h on June 19, 2025, June 25, 2025, June 30, 2025, July 04, 2025 and July 29, 2025, respectively. This case highlights the layered challenges of conversion THR in a young patient: acetabular reconstruction, instability control, intraoperative femoral fracture management, culture-positive Gram-negative infection and biochemical monitoring after debridement and targeted antibiotics.