A proposed mechanism for squeaking of ceramic-on-ceramic hips

Ceramic-on-ceramic (COC) bearings for hip arthroplasty have shown low wear rates and low biological reactivity of wear particles. However, a clinical complication receiving increased attention is the phenomenon of squeaking in COC hips and its importance in terms of clinical performance of the bearings. The recent literature presents a wide spectrum of factors claimed to be the cause of squeaking of ceramic hips, and a clear determination of the factors leading to squeaking has been elusive. The current study documents that the ceramic ball-in-socket bearing couple alone, without any metal devices incorporated, can be made to vibrate at an audible frequency when articulated. Consideration of the geometry of current generation ceramic-on-ceramic hip bearings leads to an hypothesis of a rolling/sliding mechanism causing vibration and squeaking. The derived relationship appears to accurately model the frequencies of the noise from hip bearings. Laboratory tests using accelerometers support the predicted relationship between bearing friction and femoral head motion, providing evidence that the proposed roll/slide mechanism reflects the type of motion that occurs during flexion of a modern COC hip device.