Dissociation of the femoral head and trunion after constrained conversion total hip arthroplasty for poliomyelitis.

A conversion total hip arthroplasty using a 58-mm cementless shell and screws and constrained acetabular liner was performed in a 71-year-old patient with a nonunion of an intertrochanteric fracture and poliomyelitis with flail extremities. Preoperatively, the fractured lower extremity was painful and normally used by the patient for pivot transfers from his wheelchair. Five months postoperatively, the patient sustained complete dissociation of the trunion and femoral head, which was still located within the constrained liner. All other components were well fixated and properly positioned. The hip was revised successfully with a 40-mm femoral head and a nonconstrained liner with a 15 degrees elevated lip placed posterosuperiorly.