Abstract
INTRODUCTION
The development of new bearing surfaces for total joint replacement is constantly evolving. Oxidized zirconium (Oxinium) has been introduced for use in both total hip arthroplasty (THA) and total knee arthroplasty (TKA). The aetiology of wear is multifactorial and includes adhesive, abrasive, third-body and fatigue wear mechanisms. Oxinium femoral components have demonstrated clear improvements in wear characteristics in-vitro. The purpose of this prospective study was to evaluate the mid-term (minimum 5 year) clinical and radiographic results and survivorship of the Genesis II™ knee implant system using an Oxinium femoral component.
METHODS
Between January 2001 and December 2008, 382 Genesis II Oxinium (Smith & Nephew) primary total knee arthroplasties (TKA) (313 patients) were implanted at our institution. A comparison with a cohort of 317 patients (382 knees) who received a Genesis II knee implant using a ‘conventional’ cobalt-chrome (Co-Cr) femoral component was performed during the same time period. Prospective data was collected on all patients including demographics (age, BMI, diagnosis) as well as pre and postoperative clinical outcome scores (SF-12, WOMAC, and knee society clinical rating scores (KSCRS). Radiological analysis for evidence of osteolysis and loosening was performed in all patients. Comparisons were performed to determine differences between the Oxinium and Cobalt Chrome cohorts. Kaplan-Meier survival analysis was performed to show cumulative survival over time. Failure was defined as femoral component revision due to any cause.
RESULTS
The mean age at time of surgery was 54.0 and 60.6 years respectively for the Oxinium and Co-Cr groups. The mean time from surgery was 8.13 +/− 2.03 years and 8.59 +/− 2.01 years for the Oxinium and Co-Cr groups respectively. Both groups demonstrated a statistically significant improvement in clinical outcome measures between pre, and post operative SF-12, WOMAC, and KSCRS scoring systems with no difference between two groups. There were a total of 15 revisions (infection: 8, stiffness: 2, aseptic loosening of patella component: 2, Aseptic loosening of the tibial component: 1, instability: 1, and one malaligned Femoral Component) in the Oxinium group. In the CoCr group there were a total of 9 revisions (Infection:5, aseptic loosening:1, instability: 1, stiffness: 1 and one patient revised for unexplained pain). Radiographically, no loosening was noted in the Oxinium group and all implants appeared well fixed. There was one case of loosening seen in the cobalt chrome group. The overall survival was 99.7 for both Oxinium and CoCr femoral components. Our study demonstrated no significant differences in validated clinical outcome scores and radiographic outcomes when comparing the Oxinium and Co-Cr femoral components
CONCLUSION
Despite the large numbers in our study, there were no statistically significant differences between Oxinium and CoCr femoral components at a minimum of five years follow up. While no clear benefits have been demonstrated, the use of an Oxinium femoral component demonstrated no adverse events at mid-term follow-up. Conventional Co-Cr femoral components remain the gold standard while long-term follow-up data is required to demonstrate the potential benefits of Oxinium.
