Fracture of a polyethylene acetabular cup: a case report

Fracture of a polyethylene acetabular cup is rare. Current theories of its cause emphasize wear of the component. The case reported illustrates the presence of a loosening membrane in association with cup fracture. Histologic study of the loosening membrane indicated a foreign-body reaction to polyethylene and acrylic wear particles. The authors propose a theory relating micromotion of the acetabular component to the production of particles of wear with a subsequent foreign-body reaction followed by further loosening. The erosion of bony support leads to the concentration of stress at the junction of the supported and unsupported segments. This may ultimately result in fracture of the cup.