Abstract
Abstract
Purpose
Fixed‐bearing lateral unicompartmental knee arthroplasty (UKA) is a bone‐ and ligament‐preserving treatment option for isolated lateral‐compartment osteoarthritis (OA), but evidence in younger patients remains limited. The primary purpose of this study was to assess lateral component revision‐free survival and reoperation‐free survival following primary fixed‐bearing lateral UKA in patients aged 55 years or younger. Secondary objectives were to evaluate functional and radiological outcomes.
Methods
This retrospective case series was derived from a prospectively maintained institutional database. A consecutive series of 84 primary fixed‐bearing lateral UKAs in 80 patients aged ≤55 years, performed between January 2016 and December 2021 with a minimum follow‐up of 2 years was identified (mean follow‐up, 5.3 ± 1.9 years [range, 2.2–8.6 years]; mean age, 51 years [range, 37–55 years]). Kaplan‐Meier analysis estimated 5‐year survival for lateral component revision or reoperation. Lateral component revision was defined as the removal or exchange of any fixed implant component (femoral or tibial). Reoperation was defined as any subsequent surgical procedure on the operated knee. Functional outcomes were evaluated using the Oxford Knee Score (OKS) and University of California, Los Angeles Activity Score. Radiographic assessment included measurement of the hip‐knee‐ankle angle (HKAA).
Results
Lateral component revision‐free survival was 100%, while cumulative reoperation‐free survivorship was 92.5% (95% CI: 86.8–98.2) at 5 years. Seven reoperations were observed: 4 additional medial UKAs, 2 arthroscopic procedures and 1 successful debridement, antibiotics and implant retention (DAIR). Mean HKAA changed from 4.8° ± 4.7° valgus preoperatively to 2.0° ± 2.8° valgus postoperatively. Postoperative HKAA demonstrated higher residual valgus in knees without medial‐compartment OA progression or osteonecrosis (ON) compared to four knees with medial‐compartment OA or ON (2.2° valgus vs. 1.5° varus,
p
= 0.012). The mean postoperative OKS was 43.8 ± 5.7 and the UCLA Activity Score was 6.5 ± 1.2.
Conclusions
Fixed‐bearing lateral UKA in younger patients was associated with 100% lateral component revision‐free survival and high functional scores at a mean follow‐up of 5 years. No implant‐related failures, such as aseptic loosening, were observed in this active cohort, although seven knees underwent reoperation, including four additional medial UKAs. Progression of OA in the medial compartment was the most common reason for reoperation. The observed association between postoperative varus alignment and medial‐compartment OA progression or ON is limited by the small number of events and requires further investigation.
Level of Evidence
Level IV.