Three years after total hip replacement surgery, a patient's modular femora
l head separated from the stem portion of a primary total hip replacement w
hile 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 great
ly increases the flexibility during primary or revision total hip arthropla
sty, but introduces the risks of component dissociation and intraoperative
errors in matching. We report an unusually late dislocation of a primary mo
dular total hip replacement.