Bicruciate-retaining total knee arthroplasty procedure reduced tensile force in the middle and posterior components of lateral collateral ligament during deep knee flexion activities with no effect on tensile force of the medial collateral ligament.

Purpose: To analyse the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on the tensile force of the collateral ligaments during two deep knee flexion activities, cross-leg sitting and squatting.

Methods: Thirteen patients (15 knees) treated using bicruciate-retaining total knee arthroplasty (BCR-TKA) for knee joint osteoarthritis were analysed. Knee joint kinematics during cross-leg sitting (open-chain flexion) and squatting (closed-chain flexion) were evaluated through fluoroscopy. The tensile force was calculated in vivo based on the change in the distance between the femoral and tibial attachment areas for the anterior, middle, and posterior components of the superficial (sMCL) and deep (dMCL) medial collateral ligament and the lateral collateral ligament (LCL). Differences in the calculated tensile forces of the collateral ligaments were evaluated using repeated measures of analysis of variance, with post hoc pairwise comparison (Bonferroni test). Statistical significance was set at P ≤ 0.05.

Results: The correction of the coronal alignment was related to the surgical technique, not to the implant design. No significant change in the tensile force in all three components of the sMCL from pre- to post-TKA (n.s.) was observed. For dMCL, a pre- to post-TKA change in the tensile force was observed only for the anterior dMCL component (p = 0.03). No change was observed in the tensile force of the anterior LCL with increasing flexion, with no difference in pre- to post-TKA and between activities (n.s.). In contrast, tensile force in the middle LCL slightly decreased with increasing flexion during squatting, pre- and post-TKA. After surgery, lower forces were generated at 40° of flexion (p = 0.04). Tensile force in the posterior LCL was higher in extension than flexion, which remained high in the extension post-TKA. However, after surgery, lower tensile forces were generated at 10° (p = 0.04) and 40° (p = 0.04) of flexion.

Conclusions: The in vivo change in tensile forces of the collateral ligaments of the knee before and after BCR-TKA can inform the development of appropriate ligament balancing strategies to facilitate recovery of deep knee flexion activities after TKA, as well as for continued improvement of BCR-TKA designs.

Level Of Evidence: III.