Dissociation of modular polyethylene liner. A, After placement of metal-backed acetabular component with modular polyethylene liner. B, Six weeks after surgery, hip dislocated while patient was sitting in low chair. After reduction maneuver, femoral head is eccentrically located in metal backing. Radiolucent shadow of displaced polyethylene liner is visible in soft tissues inferiorly (arrows). Reoperation was required to replace liner.