Intrapelvic Cup Migration Following Revision Total Hip Arthroplasty: A Case Report and Review of the Literature.

Intrapelvic acetabular cup migration is a rare but serious complication that can occur following either primary or revision total hip arthroplasty. Medial acetabular wall weakening is considered the main predisposing factor for acetabular protrusion. A thorough preoperative plan is essential to advocate proper pelvic anatomy reconstruction, including osteosynthesis of the pelvis, if necessary, preservation of muscle and bone stock, and selection of the right prosthetic components without damaging adjacent anatomical structures. We present a rare case of an 84-year-old woman with a hip dislocation and complete intrapelvic migration of the acetabular component, nine years after her second revision surgery of a hip prosthesis placed 60 years ago due to congenital hip dysplasia. The protruded acetabulum was not removed since preoperative CT and digital subtraction angiography (DSA) revealed no vascular compromise. A non-cemented, tantalum acetabular cup, reinforced by a short flange titanium acetabular cage, was placed with a cemented, polyethylene-bearing surface, which was revised to a cemented, constrained acetabular insert three months postoperatively due to dislocation after mobilization on the bed. We conducted a literature review to elucidate the causes, proper diagnostic tools, and preoperative planning of this rare occurrence while trying to evaluate a potential treatment protocol.