No difference in the use of revision components and re- revision rate in conversion to total knee replacement fol- lowing Oxford Partial Knee Microplasty Instrumentation: a registry study of 529 conversions

Background and purpose - Microplasty Instrumenta-tion was introduced to improve Oxford Mobile Partial Knee placement and preserve tibial bone in partial knee replace-ment (PKR). This might therefore reduce revision complex-ity. We aimed to assess the difference in use of revision total knee replacement (TKR) tibial components in failed Micro-plasty versus non-Microplasty instrumented PKRs. Patients and methods - Data on 529 conversions to TKR (156 Microplasty instrumented and 373 non-Micro-plasty instrumented PKRs) from the Dutch Arthroplasty Register (LROI) between 2007 and 2019 was used. The primary outcome was the difference in use of revision TKR tibial components during conversion to TKR, which was cal-culated with a univariable logistic regression analysis. The secondary outcomes were the 3-year re-revision rate and hazard ratios calculated with Kaplan-Meier and Cox regres-sion analyses. Results - Revision TKR tibial components were used in 29% of the conversions to TKR after failed Microplasty instrumented PKRs and in 24% after failed non-Microplasty instrumented PKRs with an odds ratio of 1.3 (CI 0.86-2.0). The 3-year re-revision rates were 8.4% (CI 4.1-17) after con-version to TKR for failed Microplasty and 11% (CI 7.8-15) for failed non-Microplasty instrumented PKRs with a hazard ratio of 0.77 (CI 0.36-1.7). Conclusion - There was no difference in use of revision tibial components for conversion to TKR or in re-revision rate after failed Microplasty versus non-Microplasty instru-mented PKRs nor in the 3-year revision rate.