Distinctions of introarticular force distribution between genesis‐II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

Background: Although both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra‐articular force distribution. In this study, we investigated the distinctions in intra‐articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis. Methods: Forty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra‐articular force measurement system, the intra‐articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients. Findings: The total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8% –84.0% of total force in posterior stabilized knees, while 27.4% –65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P = 0.444), but force was significantly concentrated in the lateral side during 45° –120° flexion (P = 0.000– 0.028). Interpretation: Although the entire intra‐articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed. Highlights:Total force was similar in the two common types of total knee arthroplasty.Force distribution differed in the two types of total knee arthroplasty.Force in posterior stabilized knees was concentrated in the medial compartment.Force in cruciate retaining knees was well balanced at mid‐flexion.Force in cruciate retaining knees shifted to the lateral side at end flexion.