Malseating of a Titanium-Encased Ceramic Liner in a Nonhemispherical Cup during Total Hip Arthroplasty

A recent report stated that 10% of total hip arthroplasties performed with a nonhemispherical acetabular cup with a titanium-encased ceramic liner were not properly seated. We evaluated 71 consecutive total hip arthroplasties performed by a single surgeon with this same acetabular implant system. During each procedure, the stability of the ceramic liner was carefully assessed and tested after insertion. On careful radiographic examination, 8.5% (6/71) of the titanium-encased ceramic liners were malseated. Malseating was subtle in all 6 cases and was noted in only 1 case before this study’s dedicated radiographic review. One patient had a fall and required revision as the liner became dissociated from the shell and the shell loosened from the pelvis. The remaining 5 patients have continued to be asymptomatic and appear to be stable; however, we will continue to routinely examine these patients for either dissociation or metal fretting secondary to micromotion of the titanium-encased liner.