Custom-Made Monoflange Acetabular Component for Revision Hip Arthroplasty in Paprosky Type IIIA Defect: A Case Report

Severe acetabular bone loss in revision total hip arthroplasty (THA), particularly Paprosky type IIIA defects, remains a major reconstructive challenge. Conventional off-the-shelf implants often fail to achieve adequate primary stability and durable fixation in such cases. Custom-made acetabular components, designed using computed tomography (CT)-based three-dimensional (3D) planning, offer a defect-specific reconstructive option in selected cases by optimizing implant fit, fixation, and restoration of hip biomechanics.

We report the case of a 30-year-old male who presented with progressive hip pain and limp 9 years after primary THA performed for a femoral neck fracture secondary to an aneurysmal bone cyst. Imaging revealed extensive periacetabular osteolysis with component migration, consistent with a Paprosky type IIIA acetabular defect. Infection and malignancy were excluded through laboratory investigations, biopsy, and advanced imaging. Due to the severity of bone loss and the inadequacy of standard revision options, acetabular reconstruction was performed using a CT-based, custom-made flange acetabular component with pre-planned screw trajectories and a cemented liner. Rigid primary fixation was achieved, followed by protected weight bearing and gradual rehabilitation.

Postoperative radiographs confirmed accurate implant positioning and stable fixation. At 6 months and 1-year follow-up, the patient demonstrated significant pain relief, independent ambulation without support, and stable radiographic fixation without evidence of migration or loosening. The custom implant provided effective restoration of the hip center of rotation with satisfactory short-term clinical and radiological outcomes.

Custom-made monoflange acetabular components represent a viable and effective treatment option for managing severe acetabular bone loss in revision THA. CT-based 3D planning is critical for precise implant design, safe fixation, and restoration of hip biomechanics. Although technically demanding and resource-intensive, this approach may provide reliable short-term reconstruction in carefully selected complex revision scenarios where conventional implants are unsuitable. Further studies with larger cohorts and longer follow-up are required.