Preserving primary medial static stabilizer ligaments achieves physiological knee kinematics in total knee arthroplasty

Purpose: As postoperative knee instability has been reported to be one of the critical reasons for early failure in total knee arthroplasty (TKA), obtaining optimal knee stability—especially in medial—was indispensable for successful TKA. We hypothesized that preserving medial soft tissue structures was the key to maintain physiological medial knee stability. Thus, TKAs with preserving primary medial static stabilizer ligaments technique were performed, and the postoperative knee kinematics was evaluated. Methods: Primary knee osteoarthritis patients with varus knee deformity and planed for primary TKA were enrolled. However, patients with severe varus knee deformities, valgus knee deformities, and rheumatoid arthritis were excluded. TKAs were performed by removing medial femoral and tibial osteophytes; however, the primary medial static stabilizer ligaments—the superficial medial collateral ligament (MCL), deep MCL, and posterior oblique ligament—were not released. The cruciate-retaining (CR), posterior-stabilized (PS), and medial-pivot (MP) inserts were implanted, and the knee kinematics was measured. These data were statistically analyzed using analysis of variance. The institutional review board approved the study. Results: From full extension to maximum flexion, the lateral femoral condyle moved backward, greater than the medial femoral condyle, and consequently the femur external rotated on the tibia. These kinematics patterns were shown in CR, PS, and MP groups. Conclusion: As the knee kinematics of CR and PS are similar to that of MP, which has been reported to demonstrate physiological knee kinematics, preserving primary medial static stabilizer ligaments technique could potentially preserve physiological knee kinematics.