Unicompartmental knee arthroplasty after failed high tibial osteotomy in appropriately selected patients: a...

High tibial osteotomy (HTO) is an established treatment for medial knee osteoarthritis in younger, more active patients than typical arthroplasty candidates, but some may require conversion over time. Total knee arthroplasty (TKA) has traditionally been the preferred procedure after failed HTO. With advances in implant design and surgical techniques, the role of medial unicompartmental knee arthroplasty (UKA) in this setting warrants re-evaluation. This systematic review and meta-analysis aims to summarize and descriptively compare the outcomes of UKA and TKA following HTO.

A systematic review and meta-analysis was conducted on MEDLINE, Embase, Scopus, and Web of Science until 14th August 2025 (date last searched). Randomized and observational studies (cohort, case-control, and case series) reporting outcomes of UKA or TKA following HTO were included, while case reports, technical notes, reviews, and studies without sufficient data were excluded.

Forty-one studies (6 UKA-only, 33 TKA-only, and 2 comparative studies contributing to both groups) met inclusion criteria. Due to the limited number of comparative studies, comparisons between procedures are indirect/descriptive and should not be interpreted as evidence of relative treatment performance. After HTO, UKA demonstrated pooled revision and reoperation rates of 10.2% (95% CI = 4.5-21.6%, I² = 61.6%) (in 226 knees) and 14.4% (95% CI = 9.1-21.9%, I² = 37.0%) (in 226 knees), respectively, with PJI rates of 0-3.3% (in 71 knees). Mean improvement in the Knee Society Score (KSS) ranged from 34.09 to 38.80 points. For TKA, the pooled revision, reoperation, and PJI rates were 5.0% (95% CI = 3.5-7.2%, I² = 79.5%) (in 6208 knees), 11.1% (95% CI = 7.3-16.3%, I² = 92.8%) (in 6236 knees), and 2.9% (95% CI = 2.0-4.0%, I² = 33.5%) (in 2107 knees), with a KSS improvement range of 25.0 to 57.0 points. Direct comparative studies found no significant differences in survivorship or function. In an exploratory analysis of studies published after 2020, the revision rate for UKA and TKA was 6.3% and 3.9%, respectively. The most common cause of UKA revision was lateral progression of osteoarthritis. The meta-analysis showed a pooled infection rate of 2.9% (in 2107 knees) following TKA.

This study suggests that UKA after HTO should not be considered an absolute contraindication and may have a role in a carefully selected subset of patients with isolated medial osteoarthritis, sufficient MCL, and acceptable residual alignment. However, these findings should be interpreted cautiously, as the current evidence base consists predominantly of retrospective observational studies. Accordingly, the present findings should be viewed as hypothesis-generating rather than as evidence establishing equivalence or comparative effectiveness between UKA and TKA after failed HTO. Prospective comparative studies are needed to better define its effectiveness relative to TKA, refine patient selection algorithms, and clarify the influence of residual deformity on outcomes.

Level III, systematic review and meta-analysis.