JOA - 2026-09-04 - Journal Article
Preoperative Medial Proximal Tibial Angle of Less Than 84° Does Not Compromise Two-Year Clinical Outcomes After Unrestricted Kinematic Alignment Total Knee Arthroplasty: A Propensity Score-Matched Study.
Ng Y, Lim WSR, Lam LZL, Escarda JL, Lee M, Yeo SJ
Topics
Key Takeaway
Unrestricted KA-TKA in patients with severe proximal tibial varus (mean MPTA 81.6°) achieved equivalent 2-year PROMs and satisfaction rates comparable to less-deformed KA patients and superior satisfaction versus MA-TKA (p=0.017).
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Summary
This propensity score-matched retrospective study compared 2-year outcomes of unrestricted KA-TKA stratified by preoperative MPTA ≥84° (n=156) versus <84° (n=82) against MA-TKA controls (n=476) in a Southeast Asian population. At 2 years, KSKS was significantly better in the MPTA ≥84° KA group versus MA-TKA (p=0.032), while the severe varus KA group (MPTA <84°) showed no significant difference in any PROM versus either KA subgroup or MA-TKA. Both KA groups demonstrated significantly higher patient satisfaction than MA-TKA at 6 months and 2 years (p=0.015 and p=0.017), with only 2 surgical revisions across all 714 knees.
Key Limitation
Two-year follow-up is insufficient to determine whether tibial components placed in unrestricted varus will demonstrate accelerated loosening, polyethylene wear, or medial compartment overload at mid- to long-term intervals.
Original Abstract
INTRODUCTION
Unrestricted kinematic alignment (KA) total knee arthroplasty (TKA) may accept tibial component varus beyond conventional thresholds, yet outcomes in marked proximal tibial varus remain understudied in Southeast Asian populations. Our study evaluated two-year outcomes after unrestricted KA-TKA in patients who had severe proximal tibial varus, using mechanically aligned TKA (MA-TKA) as control.
METHODS
This retrospective, propensity score-matched cohort study included 238 unrestricted KA-TKAs and 476 MA-TKAs with minimum two-year follow-up. The KA cohort was stratified by preoperative medial proximal tibial angle (MPTA): ≥ 84° (Group 1, n = 156, mean MPTA 86.6°) versus less than 84° (Group 2, n = 82, mean MPTA 81.6°). The following variables were compared: (1) demographic data, (2) patient-reported outcome measures (PROMs) including Short-Form 36 (SF-36) domains, Oxford Knee Score (OKS), Knee Society Function and Knee Score (KSFS and KSKS), patient satisfaction and expectations, and (3) radiological parameters including MPTA, lateral distal femoral angle, arithmetic hip-knee-ankle angle, and joint line obliquity. Kaplan-Meier analysis assessed revision-free survival.
RESULTS
At six months, Group 1 demonstrated significantly better KSKS than Group 2 and MA-TKA (P = 0.033 and P < 0.001, respectively). This persisted for two years, with Group 1 achieving significantly better KSKS (P = 0.032) than MA-TKA, but not against Group 2 (P = 0.555). There were no between-group differences detected for other PROMs, but significantly more patients were satisfied in Groups 1 and 2 compared with MA-TKA at six months and two-year follow-up (P = 0.015 and P = 0.017, respectively). Kaplan-Meier curves showed excellent two-year revision-free survival with two surgical revisions and four knee manipulations.
CONCLUSION
At two-year follow-up, in patients who have severe proximal tibial varus (mean MPTA 81.6°), unrestricted KA-TKA achieved comparable PROMs, excellent patient satisfaction, and survivorship relative to patients who had less severe deformity and the MA-TKA cohort.