JOA - 2026-09-21 - Journal Article
Preoperative Medial Proximal Tibial Angle Does Not Influence Clinical Outcomes Following Mobile-Bearing Unicompartmental Knee Arthroplasty.
Kinoshita T, Bunyoz KI, Mortensen KRL, Jensen CB, Gromov K, Troelsen A
Topics
Key Takeaway
Preoperative MPTA did not influence OKS improvement at 2 years following mobile-bearing medial UKA across three MPTA strata (≤83°, 84–86°, ≥87°), though varus tibial component alignment produced significantly greater OKS gains in the ≤83° MPTA subgroup.
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Summary
This retrospective study stratified 454 consecutive mobile-bearing medial UKA patients by preoperative MPTA (≤83°, 84–86°, ≥87°) to determine whether proximal tibial varus anatomy affects functional outcomes. OKS improvements from baseline to 3 months, 1 year, and 2 years were statistically comparable across all three MPTA groups, and postoperative tibial component alignment distribution did not differ significantly between groups (P=0.280). Within the ≤83° MPTA subgroup, varus tibial component alignment was associated with significantly greater OKS improvement at all time points, suggesting anatomy-specific alignment targets may matter most in patients with pronounced preoperative varus.
Key Limitation
Two-year follow-up is inadequate to detect survivorship differences attributable to tibial component malalignment, which typically manifest as progressive tibial subsidence or bearing dislocation beyond 5 years.
Original Abstract
BACKGROUND
The aim of this study was to evaluate whether preoperative medial proximal tibial angle (MPTA) influences clinical outcomes following mobile-bearing medial unicompartmental knee arthroplasty (UKA).
METHODS
This retrospective study included 454 consecutive patients who had antero-medial osteoarthritis and underwent mobile-bearing medial UKA performed by two surgeons at a single institution between August 2016 and May 2023. Patients were stratified into three groups according to preoperative
MPTA
≤ 83° (n = 84), 84 to 86° (n = 229), and ≥ 87° (n = 141). Within each group, clinical outcomes were further compared according to postoperative tibial component alignment (TCA) using group-specific varus thresholds. Clinical outcomes were assessed using the Oxford Knee Score (OKS) preoperatively and at three months, one year, and two years postoperatively. Pairwise comparisons of changes in OKS were conducted using a general linear model with Bonferroni-adjusted post hoc tests, and adjusted mean differences were calculated after controlling for age, sex, and body mass index.
RESULTS
Improvements in the OKS from baseline to three months, one year, and two years were comparable among the preoperative MPTA groups. Postoperative TCA also did not differ significantly between groups (P = 0.280). In the MPTA ≤ 83° group, varus TCA was associated with significantly greater improvements in OKS at each time point.
CONCLUSION
Preoperative MPTA did not significantly influence clinical outcomes following UKA, suggesting that increased proximal tibial varus may not adversely affect two-year outcomes. Alignment strategies tailored to preoperative MPTA may help optimize postoperative outcomes.