Spectral characterization of squeaking in ceramic-on-ceramic total hip arthroplasty: Comparison of in vitro and in vivo values

Squeaking is a cause for concern in total hip arthroplasty (THA). However, the definition of this sound remains vague. Our goals were to characterize spectrally the squeaking in vitro under lubricated conditions and to compare the in vitro frequencies to in vivo frequencies. Four patients, who presented with a squeaking after ceramic-on-ceramic THA were investigated. In addition, 3 alumina ceramic 32 mm diameter components were tested in vitro under edge loading conditions using a friction simulator. Tests were conducted under lubricated conditions without and with the addition of a third body alumina particle. In vitro, no squeaking occurred under edge loading conditions. However, with the addition of a third body particle in the contact region, squeaking was obtained; the dominant frequency was 2.6 kHz. In vivo, the main recorded sound frequencies were: 2.3, 2.24, and 2.46 kHz for squeakers during walking and 1.45 kHz for a squeaker rising from a bent position. The in vivo recordings had a dominant frequency similar to, but slightly lower than, the in vitro values. Two types of squeaking were found in vivo and characterized spectrally. The rising squeaker had intermittent squeaking corresponding to a lower fundamental frequency compared to the walking squeakers. This finding suggests two different mechanism of squeaking.