Posterior capsular release improves intraoperative flexion contracture without affecting knee kinematics in posterior-stabilized total knee arthroplasty.

Objectives: Posterior capsular release (PCR) is widely performed in total knee arthroplasty (TKA) for late-stage knee osteoarthritis with severe flexion contracture. PCR enables obtaining an appropriate bone gap, resulting in an improvement in the knee extension angle after TKA. Despite its efficacy, little is known about its influence on knee kinematics. This study aimed to measure the change in knee extension angle after PCR in TKA and clarify its influence on knee kinematics.

Methods: Posterior-stabilized (PS) TKA was performed on eight cadaveric knees under Thiel fixation using a navigation system. In the trial component setting, the knee extension angle was measured. Subsequently, we performed PCR at the intercondylar fossa. The maximum knee extension angle and knee kinematics, which were calculated using the anteroposterior, compression-distraction, and mediolateral positions and the rotational knee angle obtained from the navigation system, were measured before and after PCR. Then, changes in the knee extension angle and knee kinematics were assessed following PS-TKA and intraoperative PCR.

Results: PCR at the intercondylar fossa resulted in a significant 9.1 ​± ​3.6° improvement in the knee extension angle (P ​= ​0.01). The anteroposterior position of the femur relative to the tibia throughout the range of motion did not change significantly after PCR. Regarding rotational knee kinematics, six cases showed a parallel pattern and two showed a medial pivot pattern with PS-TKA before PCR. Rotational knee kinematics did not change after PCR in any case.

Conclusion: PCR at the intercondylar fossa is a critical surgical technique for addressing intraoperative flexion contracture in PS-TKA without affecting intraoperative knee kinematics.

Level Of Evidence: III.