Rotational laxity at 30° of knee flexion is associated with postoperative clinical outcomes after bi-cruciate stabilized total knee arthroplasty.

Abstract

Achieving favorable clinical outcomes after total knee arthroplasty (TKA) requires appropriate soft tissue balance. Although sagittal and coronal plane stability have been extensively studied, limited data exist regarding axial plane laxity. This study aimed to quantify rotational joint laxity intraoperatively and examine its association with postoperative outcomes. Thirty-six patients who underwent bi-cruciate stabilized (BCS) TKA with navigation were included. Rotational angles between the tibia and femur were measured intraoperatively at 0°, 30°, 60°, 90°, and 120° of knee flexion under neutral, internal, and external rotational stress conditions. Total rotational laxity was defined as the difference between internal and external stress positions; internal and external laxities were calculated relative to the neutral position. Postoperative outcomes were evaluated at one year using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and range of motion. Correlations between rotational parameters and clinical outcomes were analyzed. Total rotational laxity at full extension was significantly smaller than at flexed positions. Internal laxity was significantly greater than external laxity at several flexion angles. KOOS-ADL scores were positively correlated with total and internal rotational laxity at 30°, whereas maximum flexion angle was negatively correlated with external rotational laxity at 30°. Rotational joint laxity at 30° may be associated with postoperative clinical outcomes after BCS TKA. However, given the multiple correlation analyses performed, the potential risk of type I error should be considered when interpreting these findings.