Reduced 5-Year Risk for Revision of the Oxford UKA Using New Instrumentation versus Conventional Instrumentation: A Registry Study of 12,867 UKAs

Abstract

Background and purpose: Microplasty instrumentation was introduced for a more consistent surgical implantation technique, especially component alignment and tibial resection level, of the Oxford medial unicompartmental knee replacement (UKA) and thereby aims to improve UKA survival. This study aimed to assess the 5-year risk for revision and reasons for revision of the Oxford medial UKA using the new instrumentation (Microplasty) with its predecessor, i.e., conventional instrumentation (Phase 3). Patients and Methods: Data of all medial UKAs from the Dutch Arthroplasty Register (LROI) between 2007-2019 were collected. Type of instrumentation was divided into new (Microplasty) and conventional instrumentation. Kaplan-Meier analysis was performed to calculate 5-year cumulative revision percentage with any reason for revision as endpoint. A multivariable Cox regression with outcome revision of UKA adjusted for age, gender, American Society of Anesthesiologists-score, surgical history, and type of fixation was performed. Additionally, reasons for revision at 3-year were assessed and tested through Fisher’s exact tests. Results: 12,867 Oxford medial UKAs, 8,170 using new and 4,697 using conventional instrumentation, were included. The 5-year revision percentage was 9.2% (CI 8.4-10.1%) for UKAs using the conventional and 6.1% (CI 5.4-6.7%) for new instrumentation. The adjusted hazard ratio for revision at 5-year follow-up was 0.68 (CI 0.59-0.79) in favor of UKAs using the new instrumentation. Malalignment was less frequently registered as reason for revision in UKAs using the conventional compared to the new instrumentation (16.2% versus 7%; p=0.001). Interpretation: Our results show a reduced 5-year risk for revision of the medial Oxford UKAs using the new compared to the conventional instrumentation. This might be the result of a lower revision rate for malalignment in UKAs using the new instrumentation.

Early outcomes of the Oxford unicompartmental knee arthroplasty: 140 cases from a single institute in Taiwan

“…11,17 Using MP, OUKA has achieved superior clinical and radiologic outcomes. 9,11,18,19 The study by Gaba et al 11 of Indian patients reported excellent short-term outcomes for OUKA with MP, with an average Oxford Knee Score (OKS) of 39.5 ± 5.7, and 91.2% of patients achieved good or excellent OKS.…”

“…In OUKAs with MP, malalignment was a less frequent reason for revision compared with conventional OUKAs (7.5% vs 16%; p = 0.001). 18 A study conducted in Italy demonstrated that MP is more effective than OUKA phase 3 in terms of determining the tibial cut and improving the tibial slope. 19 Most patients included in our study fell within the tolerance range for radiographic parameters for both femoral and tibial component positions, which is consistent with findings from previous research.…”