Squeaking in total hip replacement: no cause for concern.

Traditional total hip arthroplasty (THA) using metalon-polyethylene bearings has been established as a reliable procedure, but polyethylene wear and wear debris–associated osteolysis are among the most frequent reasons for revision.1 Hard-bearing-surface THAs with improved tribological properties have been introduced to decrease wear and wear debris–induced osteolysis. Among the hardbearing alternatives, alumina ceramic-on-ceramic bearings have consistently shown low wear and biological reactivity to wear particles. Clinically, ceramic-on-ceramic hip arthroplasties with modern metal-backed alumina cups have demonstrated excellent clinical outcomes with low revision rates,2,3 with complications such as acetabular liner, femoral head fractures, or chipping occurring rarely.4 Curiously, after more than 30 years of clinical experience with alumina ceramic-on-ceramic bearings worldwide and with 2 closely studied longterm FDA studies in the United States,2,3 a new phenomenon of frequent, clinically reproducible squeaking was reported, primarily beginning in 2006. Further, these reports were authored by surgeons who had little, if any, experience with alumina ceramic-on-ceramic bearings during the IDE study period from 1997 to 2003. Inevitably, many theories were proposed to explain this phenomen, including mismatched ceramic bearings diameters,5 edge loading due to acetabular component malpositioning,6 disruption of fl uid fi lm lubrication with stripe wear,7 microseparation and subluxation of the femoral head,7 the use of short necks,8 and wear debris from metal-on-metal impingement in implants.9 Ultimately though, one fundamental question has remained: Why, after years of successfully using ceramic-on-ceramic THA, did this phenomenon of squeaking suddenly become frequently noted by a subset of surgeons, particularly practicing in the Unitied States? The goal of this study was to use our clinical experience with two FDA IDE studies2,3 during a period of more than 10 years to improve our understanding of this squeaking phenomenon.