A new patient-specific planning method based on joint contact force balance with soft tissue release in total knee arthroplasty

Although the conventional total knee arthoplasty (TKA) planning used 2D or 3D images of the patient's lower extremity to determine bone alignment, it was shown that good bone alignment does not always guarantee successful results due to unbalanced joint contact forces and soft tissue tension. Thus, the joint contact force balance and soft tissue tension were pre-operatively calculated using finite element analysis (FEA). Although the results of FEA are accurate, the rigid body spring method (RBSM) has introduced for the joint contact force or pressure distribution due to the high costs for FEA. In this paper, an innovative method was described to quantify the pre- and post-operative knee contact force balance using various engineering techniques, including the free-form deformation (FFD) technique, and RBSM-based cartilage contact force and ligament tension estimation algorithm. Nine cases of TKA planning were performed with three different surgical options, including over-correction of the valgus ratio of the femur, tibial plateau cutting length, and MCL release to redistribute the medial and lateral contact force balance. This method is useful as a patient-specific preoperative planning tool in TKA surgery.