THE SQUEAKING CERAMIC HIP RETRIEVAL, RADIOGRAPHIC, ACOUSTIC AND FINITE ELEMENT ANALYSES

Abstract

Squeaking in hip arthroplasty is now well-documented but hitherto poorly understood. In this paper, we report data progressively accumulated from a series of studies undertaken by our group to investigate the mechanisms of noise production associated with ceramic-on-ceramic bearings. We reviewed demographic and radiographic data comparing squeaking with silent hips. Edge loading of the acetabular components was investigated on retrieved bearings and with finite element analysis. The squeaking sound itself was further investigated through acoustic analysis. Squeaking occurs in younger, heavier, and taller patients.

We found a higher incidence of acetabular component malposition in squeaking hips and edge loading appears to be a causative factor. Finite element analysis revealed a stiffness mismatch between the shell and liner which may allow the shell to oscillate producing an audible squeak. Acoustic and modal analysis show that squeaking is due to a forced vibration and that the natural frequencies of the ceramic components are above the audible range, suggesting that resonance occurs in the metallic, not the ceramic parts. This phenomenon is related to patient factors, surgical factors, and implant factors, which may produce sound by a combination of edge loading of the ceramic and forced vibration of the acetabular shell and/or the femoral stem.