Late detachment modular femoral component after primary total hip replacement.

Three years after total hip replacement surgery, a patient's modular femoral head separated from the stem portion of a primary total hip replacement while the patient was rising from a chair. The modular femoral head was in a polyethylene acetabular socket. Modular femoral and acetabular components now widely are used in hip replacement. The use of modular components greatly increases the flexibility during primary or revision total hip arthroplasty, but introduces the risks of component dissociation and intraoperative errors in matching. We report an unusually late dislocation of a primary modular total hip replacement.