In Vivo Wear of a Squeaky Alumina-on-Alumina Hip Prosthesis

Abstract

Alumina-on-alumina bearings for total hip replacement have been in use for over three decades and are associated with good long-term clinical performance1,2. However, recently there have been anecdotal reports of audible noise, usually characterized as squeaking, in ceramic-on-ceramic joints, which have been publicized even in the media3. The reported prevalence of squeaking and noise in these bearings has varied from 10% (as reported by Varnum et al.7, Keurentjes et al.8, and Jarrett et al.9). The etiology of hip squeaking remains unclear and is undoubtedly a multifactorial phenomenon that may involve component femoral neck-cup impingement, microseparation, and subluxation10. Although limited in number, case reports on squeaky ceramic hip bearings appear to reflect this varied etiology. Thus, squeaking was seen in connection with the use of a mismatched zirconia head and alumina cup wear couple11, femoral neck-socket impingement12,13, and acetabular cup abduction and retroversion coupled with leg-length discrepancy14. There is an ongoing debate about whether squeaking of ceramic hips is a cause for concern15 or not16. Regardless of its prevalence, squeaking of ceramic-on-ceramic joints warrants investigation as it may signal abnormal wear of the bearing surfaces, which, in view of the brittle nature of ceramics, may progressively increase in severity. In the present case study, we had the opportunity to examine an alumina-on-alumina hip that was explanted because of severe persistent squeaking with all activities. The purpose of the present study was to determine if the severe noise was accompanied by substantial joint wear. We hypothesized that the squeaking was associated with degradation of the bearing surfaces. We …