Wear of a composite ceramic head caused by liner fracture.

Third-generation composite ceramics (eg, Delta; DePuy Orthopaedics, Warsaw, Indiana; Ceramtec, Plochingen, Germany) have greatly improved material characteristics compared with second-generation products. This case report presents a patient after total hip arthroplasty with a fractured ceramic liner and a heavily worn ceramic head (both third-generation ceramics) retrieved 9 months after surgery. The patient showed no symptoms in the involved hip but presented to the hospital because of other symptoms. The failure was caused by a tilted liner that was overlooked after surgery and fractured consecutively. Rim chipping and splitting were the 2 fracture modes observed for the liner. The head did not fracture completely because of its high strength but became roughened by the ceramic fragments, causing major wear of the metal back of the cup. The phase transformation of the zirconium grains from tetragonal to monoclinic in the aluminum oxide matrix was shown by radiographic diffraction analysis in the heavily worn areas of the head. This transformation increases the fracture strength of the head. Metal debris caused by a roughened ceramic head without fracture is an unreported phenomenon for third-generation ceramic bearings in hip arthroplasty. This case shows that proper impaction of the ceramic liner into the metal shell to prevent later tiling during reduction is as important as correct component positioning. If a tilted ceramic liner is observed postoperatively, the position must be corrected immediately to prevent the major consequences observed in this patient.