JOA - 2026-06-18 - Journal Article
Soft-Tissue Balance and Quadriceps Muscle Strength Are Associated with Patient-Reported Outcomes Following Total Knee Arthroplasty, Independent of Alignment Strategy: A Prospective Randomized Trial.
Ueyama H, Nakagawa S, Fukunaga K, Takemura S, Ohyama Y, Minoda Y, Sugama R, Masuda S, Terai H
Topics
Key Takeaway
In a 50-patient RCT comparing KA-TKA vs MA-TKA, alignment strategy was not an independent predictor of outcomes, while extension coronal gap angle (β=2.85, p<0.01) and quadriceps strength loss (β=0.56, p=0.03) independently predicted KSS 2011 satisfaction and functional activity, respectively.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This RCT randomized 50 patients to KA-TKA or MA-TKA using a medial pivot design, assessing soft-tissue balance intraoperatively and outcomes via KSS 2011 and quadriceps strength testing at 2 years. Despite confirmed CPAK phenotype differences between groups (p<0.01), alignment strategy did not independently predict subjective outcomes on multivariate regression. Extension coronal gap angle independently predicted KSS satisfaction (β=2.85, 95% CI 0.69–5.02), while older age and greater quadriceps strength loss independently predicted worse functional activity.
Key Limitation
The sample size of 25 per group is insufficient to detect moderate between-group differences in alignment strategy effect, making the null finding for KA vs MA potentially a type II error rather than true equivalence.
Original Abstract
BACKGROUND
Kinematically aligned (KA) and mechanically aligned (MA) total knee arthroplasty (TKA) have been widely compared; however, the relative impact of alignment strategy versus other factors on clinical outcomes remains unclear. This study aimed to investigate the independent influence of alignment strategy, soft-tissue balance, and muscle strength on subjective outcomes.
METHODS
A prospective randomized controlled trial was conducted in patients undergoing TKA with a medial pivot design. Patients were randomized to receive either KA-TKA (n = 25) or MA-TKA (n = 25) and followed for two years. Soft-tissue balance was assessed intraoperatively. Outcomes including the Knee Society Score (KSS) 2011, quadriceps muscle strength, functional scores, and radiographic coronal plane alignment of the knee (CPAK) were evaluated pre- and postoperatively. Multiple regression analyses identified independent predictors of subjective outcomes.
RESULTS
There were no significant differences between groups in demographics, preoperative parameters, or intraoperative soft-tissue balance. Postoperatively, CPAK phenotype distributions differed between two groups (P < 0.01). However, alignment strategy (KA versus MA) was not identified as a significant independent predictor of subjective outcomes. Soft-tissue balance in extension (coronal gap angle) was independently associated with KSS 2011 satisfaction (partial regression coefficient: 2.85, 95% confidence interval (CI): 0.69 to 5.02, P < 0.01). By contrast, older age (partial regression coefficient: -1.90, 95% CI: -2.85 to -0.96, P < 0.01) and greater quadriceps muscle strength loss (partial regression coefficient: 0.56, 95% CI: 0.03 to 1.09, P = 0.03) were identified as independent negative predictors of KSS 2011 functional activity.
CONCLUSION
Postoperative subjective outcomes following TKA are influenced more by soft-tissue balance and muscle strength than by the alignment strategy per se.