Preoperative varus-valgus kinematic pattern throughout flexion persists more strongly after cruciate-retaining than after posterior-stabilized total knee arthroplasty

Abstract Background Restoring normal knee kinematics is a key concern for improving patient satisfaction and functional outcomes after total knee arthroplasty (TKA). However, the influence of preoperative varus-valgus kinematics due to knee osteoarthritis on postoperative kinematics is unclear. Knee ligament function contributes to both knee stability and kinematics. The purpose of this study was to evaluate changes in varus-valgus kinematics before and after TKA using a navigation system and compare pre- and postoperative changes in kinematic patterns between cruciate-retaining (CR)- and posterior-stabilized (PS)-TKA. Methods Forty knees that underwent TKA were evaluated (CR-TKA 20; PS-TKA 20). Manual mild passive knee flexion was applied while moving the leg from full extension to flexion, the varus-valgus angle was measured automatically by a navigation system at every 10° of the flexion angle, and the kinematics were evaluated. Results Kinematic patterns throughout flexion could be classified into five types. Pre- and postoperative kinematic patterns were similar in 60% of CR-TKA patients, whereas they were similar in only 25% of PS-TKA patients. The mean change in the size of the varus-valgus angle throughout flexion showed no difference between CR- and PS-TKA. However, the distribution of changes in the size of the varus-valgus angle differed between CR- and PS-TKA. Conclusions Our results showed that 1) there are some patterns of varus-valgus kinematics under an unloading condition despite recovery of neutral alignment in extension and 2) the preoperative varus-valgus kinematic pattern persisted more strongly after CR-TKA than after PS-TKA.