Unicompartmental versus total knee arthroplasty in patients aged 60 years or older with isolated medial knee osteoarthritis and correctable varus deformity > 15° to 20°: a five-year retrospective cohort study

The role of unicompartmental knee arthroplasty (UKA) in patients aged ≥ 60 years with isolated medial knee osteoarthritis and correctable varus > 15° remains controversial. Five-year UKA and total knee arthroplasty (TKA) outcomes were compared in patients with varus > 15° to 20°. This retrospective complete-case cohort included 95 TKA and 81 UKA patients treated from February 2016 to April 2019. The five-year Hospital for Special Surgery (HSS) score was the main outcome. Secondary outcomes included visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), perioperative measures, complications, revisions, and coronal alignment. Lateral Kellgren-Lawrence and patellofemoral Iwano grades were assessed. An expanded propensity score matching model including both grades retained 70 matched pairs; pair-specific comparisons used paired t, Wilcoxon signed-rank, or exact McNemar tests as appropriate. UKA alignment from the early postoperative examination to five years was assessed with a weight-bearing primary analysis and an all-pair sensitivity analysis. UKA was associated with less blood loss, shorter operative time and incision length, and lower drainage volume (all P < 0.001); hospital stay did not differ significantly. At five years, HSS, VAS, and ROM did not differ significantly. WOMAC favored UKA in the full cohort (10.1 ± 1.6 vs. 9.4 ± 1.9; P = 0.010) but not in the expanded matched-pair analysis (10.0 ± 1.5 vs. 9.5 ± 1.8; P = 0.075). Between-group WOMAC-improvement differences remained below the 10-point minimal clinically important difference benchmark. UKA coronal alignment showed no significant longitudinal change; the 76-pair sensitivity analysis was concordant. TKA achieved hip-knee-ankle alignment closer to neutral. No revisions were identified. UKA was associated with lower perioperative burden and more favorable early scores, whereas five-year HSS, VAS, and ROM did not differ significantly. TKA achieved hip-knee-ankle alignment closer to neutral. These findings may inform individualized procedure selection in patients with the same clinical profile.