Comparisons of kinematics and range of motion in high-flexion total knee arthroplasty: cruciate retaining vs. substituting designs

The purpose of this study was to compare in vivo kinematics, range of motion, and functional outcomes in patients that received either a high-flexion cruciate retaining or a high-flexion cruciate substituting knee. Forty-eight high-flexion cruciate retaining (CR) and 47 high-flexion cruciate substituting (PS) knees were included in this study and followed for an average of 27 months (24-33). Weight-bearing and non-weight-bearing maximal flexions and functional scores were compared between two groups. For kinematics evaluations, amount of posterior femoral roll-back and internal tibial rotation from 0A degrees to maximal flexion using lateral radiographs under weight-bearing conditions were also compared. Average weight-bearing maximal flexion was 126.3A degrees in the PS group, which was significantly higher than the 115.0A degrees in the CR group. Average functional scores showed no significant difference between the two groups. In terms of kinematics, the average amount of posterior femoral roll-back during full flexion was 9.6 mm in the PS group and 6.1 mm in the CR group, which was a significant difference. However, internal tibial rotation during full flexion was not significantly different in the two groups. PS high-flexion TKA provided greater weight-bearing maximal flexion and posterior femoral roll-back than CR high-flexion TKA, although no difference in clinical outcomes was observed between the two prosthesis designs. I.