Abstract
Introduction
Previous studies of ceramic-on-polyethylene (C-PE) and ceramic-on-ceramic (COC) hip bearings have focused on outcomes following primary surgery. Less is known about the utilization or outcomes of ceramic bearings in revision total hip arthroplasty (R-THA) for the Medicare population in the US. We asked (1) what is the utilization of ceramic bearings for R-THA in the Medicare population and how has it evolved over time; (2) does the use of C-PE bearings influence outcomes following R-THA as compared with metal-on-polyethylene (M-PE); and (3) does the use of COC bearings influence outcomes following R-THA as compared with M-PE?
Methods
A total of 31,809 Medicare patients (aged > 65y) who underwent R-THA between 2005 and 2013 with known bearing types were identified from the Medicare 100% inpatient sample administrative database. Outcomes of interest included relative risk of readmission (90 days) or infection, dislocation, rerevision, or mortality at any time point after revision. Propensity scores were developed to adjust for selection bias in the choice of bearing type at revision surgery. Cox regression incorporating propensity score stratification (10 levels) was then used to evaluate the impact of bearing surface selection on outcomes, after adjusting for patient-, hospital-, and surgeon-related factors.
Results
The utilization of C-PE and COC bearings in RHA increased from 5.3% to 26.6% and from 1.8% to 2.5% between 2005 and 2013, respectively. For R-THA patients treated with C-PE bearings, there was reduced risk of 90-day readmission (Hazard Ratio, HR: 0.90, 95% CI: 0.84–0.96, p=0.007). We also observed a trend for reduced risk of infection with C-PE (HR: 0.88, 95% CI: 0.74–1.04) that did not reach statistical significance (p = 0.14). For R-THA patients treated with COC, there was reduced risk of dislocation (Hazard Ratio, HR: 0.76, 95% CI: 0.58–0.99, p=0.04). There was no significant difference in risk of rerevision or mortality for either the C-PE or COC bearing cohorts when compared with M-PE.
Discussion
The results indicate that, after adjusting for selection bias and various confounding patient-, surgeon-, and hospital-related factors, Medicare patients treated in a revision scenario with ceramic bearings exhibit similar risk of rerevision, infection, or mortality as those treated with M-PE bearings. Conversely, we found an association between the use of specific ceramic bearings in R-THA and reduced risk of readmission (C-PE) and dislocation (COC). The findings of this study support further research into the association between ceramic bearings in R-THA and lower risk of hospital readmission, dislocation, and, potentially, infection.
