Mobile-bearing insert reduced patellar contact force at knee flexion during posterior stabilized total knee...

This study aimed to compare tibial rotation and patellar contact force between mobile- and fixed-bearing total knee arthroplasty from extension to flexion by using a navigation system and patellar contact force sensor on the same patients' knees.

Thirty-one consecutive patients who had undergone a primary posterior stabilized total knee arthroplasty were included. Patellar contact forces on the medial and lateral sides were measured at each flexion angle, and tibial rotation was assessed during 30-90°, and 90-120° knee flexion. The patellar contact force and tibial rotation were measured twice with the mobile- and fixed-platform trial components and compared between the two groups.

The patellar contact force was significantly lower with mobile than with fixed-bearing total knee arthroplasty on the medial side at 120° flexion (P = .0138) and lateral side at 60°, 90°, and 120° flexion (P = .0346, P = .0127, and P = .0376). There were no significant differences in tibial rotation between the mobile- and fixed-bearing inserts during both 30-90° and 90-120° knee flexion.

Patellar contact force was significantly lower, especially on the lateral side in mobile than in fixed-bearing total knee arthroplasty, whereas no significant difference in tibial internal rotation was found between the two inserts. Mobile-bearing inserts might reduce the patellar contact force by the bearing rotation, rather than natural tibial rotation during posterior stabilized total knee arthroplasty.