Effect of Initial Tibial Resection Thickness on Outcomes of Revision UKA

Abstract

Introduction: The frequency of unicompartmental knee arthroplasty (UKA) procedures has increased rapidly over the past decade. Some conflicting evidence exists concerning UKA revision. Some studies have found UKA revisions to be comparable with primary total knee arthroplasty, whereas others have found that UKA revisions require a higher need for tibial stems and augments and have more complications and worse results. This study seeks to determine the effect of a conservative tibial resection in UKA on the ease of revision and its outcomes in a consecutive patient cohort. Methods: Between January 1988 and December 2011, 38 patients in a single surgeon’s practice underwent conversion of a medial UKA to a TKA. Clinical, functional, and radiological data was evaluated and recorded. A multiple logistic regression model was performed to examine the association between the level of initial tibial resection and the use of augment or extended stem at revision. Results: Thirty-five patients underwent 37 conversions of a medial UKA to a total knee arthroplasty. At revision, a primary total knee arthroplasty implant was used in 24 (88.8%) patients who underwent a conservative tibial resection during their UKA compared with only 3 (30%) patients who underwent an aggressive tibial resection (P<.001). The odds ratio of needing an augment or stem was 26.8 (95% confidence interval, 3.71–194) when an aggressive resection was performed compared with a conservative resection during the UKA. Conclusions: The results indicate that revision of a medial UKA can be comparable with a primary TKA when a conservative tibial resection is performed at the time of the primary UKA. It is possible to preoperatively predict which patients might need the use of augmentation and stems during UKA revision. This data should guide surgeons to strive for the most conservative UKA tibial resection possible in patients undergoing medial UKA.