Does oxidized zirconium make a difference? Midterm cohort survivorship of symmetric posterior condyle posterior-stabilized total knee arthroplasty

Abstract

Background: A novel symmetric posterior condylar design and option of a femoral component with an outer zirconium oxide layer were introduced to a successful asymmetric condylar total knee arthroplasty system in 2005. Given the paucity of information on this modifed design, we performed a study to determine its early to midterm survivorship and performance. Methods: Patients who received the Genesis II Symmetric Posterior Condyle or Legion Primary total knee (cobalt-chromium [CoCr] or oxidized zirconium-niobium [OxZr]) (Smith & Nephew) implanted at the study centre between March 2007 and December 2013 were enrolled into a prospective database. We retrospectively reviewed the database and performed survival analysis using Kaplan-Meier techniques. Results: There were 2178 patients (1359 women [62.4%]; mean age 64.6 yr; mean body mass index 35.0) with 2815 knee replacements available for analysis. Survival rates were 98.2% (95% confdence interval [CI] 97.6%-98.7%) for failure for any reason at 2 years and 96.8% (95% CI 96.0%-97.7%) at 5 years. Age (hazard ratio [HR] 0.97, 95% CI 0.94-0.997) and female sex (HR 0.45, 95% CI 0.27-0.75) were protective, whereas body mass index (HR 1.02, 95% CI 0.99-1.05) and OxZr implant (HR 1.11, 95% CI 0.57-2.18) did not influence survivorship. Oxford Knee Score values improved from a mean of 40.2 to 21.8 by 2 years (p < 0.001), with no difference between the CoCr and OxZr groups. Conclusion: The symmetric posterior condylar posterior-stabilized knee offers excellent midterm survivorship. Implant bearing surface did not have an in?uence on survivorship to 5 years, and, thus, use of OxZr implants may not be justifed.