Soft tissue-based selection of alignment and implant strategy in total knee arthroplasty is associated with comparable patient-reported outcomes despite baseline differences.

BACKGROUND

Optimal selection of alignment strategy and implant design in total knee arthroplasty (TKA) remains controversial, particularly when soft-tissue conditions vary among patients. This study investigated whether a soft tissue-based selection strategy influences clinically meaningful patient-reported outcomes.

METHODS

This retrospective case-control study included 158 TKAs (84 kinematically aligned cruciate-retaining (KA-CR) and 74 mechanically aligned bicruciate-substituting (MA-BCS)) with a minimum follow up of 2 years. Alignment strategy and implant type were selected based on preoperative soft-tissue status and deformity severity. Clinical outcomes were assessed using the Knee Society Score (KSS), KSS2011 patient satisfaction, and WOMAC scores. Minimal clinically important difference (MCID) thresholds for WOMAC subscales were determined using receiver operating characteristic analysis with patient satisfaction as the anchor. MCID achievement rates were compared between groups, and interaction analyses evaluated effect modification by preoperative mediolateral laxity after adjustment for range of motion.

RESULTS

Postoperative WOMAC scores were comparable between groups. MCID thresholds for WOMAC pain, stiffness, function, and total scores were 5.5, 5.5, 16.5, and 24.5 points, respectively. MCID achievement rates were significantly higher in the KA-CR group for WOMAC pain (79.7% vs. 59.4%, P = 0.008) and total scores (77.3% vs. 60.8%, P = 0.040). Interaction analysis showed that the effect of treatment strategy on postoperative WOMAC outcomes was significantly modified by preoperative mediolateral laxity after adjustment for range of motion.

CONCLUSION

A soft tissue-based selection strategy resulted in comparable postoperative patient-reported outcomes between KA-CR and MA-BCS TKA despite differences in baseline characteristics.