Objective: The purpose of this study was to investigate the relationship between the intraoperative joint gap and range of motion in posterior-stabilized (PS) type total knee arthroplasty (TKA) using a navigation system and a spring-loaded tensioner device.
Methods: Study subjects included 31 patients with PS-fix type TKA and 40 patients with PS-mobile type TKA, respectively. Intraoperative joint gap of both medial and lateral sides were measured with the patello-femoral joint reduced at knee flexion angles of 0, 30, 60, 90 and 130 degrees, respectively. Postoperative knee flexion angle was evaluated at one year after surgery.
Results: In the PS-fix type TKA group, the average medial joint gap changes were 2.0, 2.2, 2.4, 0.5, -1.9 and -1.7 mm at each range of motion between 30-0, 60-0, 90-0, 130-0, 130-90, and 130-60 degrees of flexion, respectively. The average postoperative flexion angle was 110.3 degrees. In the PS-mobile type TKA group, the average medial joint gap changes were 1.9, 2.3, 2.5, 1.0, -1.5 and -1.3 mm at each range of motion between 30-0, 60-0, 90-0, 130-0, 130-90, and 130-60 degrees of flexion, respectively. The average postoperative flexion angle was 120.6 degrees, and was significantly greater than the preoperative flexion angle. The medial joint gap change value of 130-90 degrees and 130-60 degrees showed a positive correlation with postoperative knee flexion angle in the PS-fix type TKA group. Conversely, there was no correlation in all pairings between joint gap change value and flexion angle in PS-mobile type TKA group.
Conclusion: In PS-fix type TKA, there is a tendency for large postoperative flexion angle when the intraoperative medial joint gap changes minimally from flexion to deep flexion. Conversely, there are no correlations between joint gap change value and flexion angle in PS-mobile type of TKA. Average postoperative flexion angles are significantly greater than preoperative flexion angles in the PS-mobile type TKA.
