Clinical and kinematic outcomes of a rotating platform posterior stabilized total knee system.

Early post-operative clinical outcomes were analyzed for subjects having a rotating platform (RP) posterior stabilized (PS) total knee arthroplasty (TKA); a subset of which underwent in vivo kinematics and produced kinematic results that compare well with subjects in previous fluoroscopic studies that were deemed excellent in nature. In total, 153 subjects (180 knees) were enrolled in the prospective clinical study. TKAs were performed by three surgeons at three North American centers. Ten subjects were randomly chosen and evaluated under fluoroscopic surveillance. Average active flexion increased from 113.3 (SD=16.6) degrees before surgery to 118.3 (SD=9.9) degrees 12-months post-operatively. American Knee Society (AKS) function score increased from an average of 57.6 (SD=18.8) points pre-operatively to 85.3 (SD=16.6) points 12-months post-operatively. For the kinematic subset, post-operative weight-bearing flexion was 115.9 (SD=8.4),while subjects achieved an average posterior femoral rollback of their lateral condyle of -5.4mm. The average femorotibial axial rotation from full extension to maximum weight-bearing flexion was 3.9 degrees (SD=3.9). Certain kinematic parameters were deemed statistically significant when determining early post-operative clinical success.

Effect of implant design on knee flexion.

From March 2006 to August 2008, 93 subjects (186 knees) underwent simultaneous bilateral total knee arthroplasty performed by eight surgeons at North American centers. This randomized study was conducted to determine whether non-weight-bearing passive flexion was superior for knees receiving a posterior stabilized high flexion device compared to a posterior stabilized standard device in the contra-lateral knee. Weight-bearing single leg active flexion was one secondary endpoint. Follow-up compliance was 92.5%. Results show small, but significant superiority in the motion metrics for the high flexion device compared to the standard device 12 months after surgery, especially for a subgroup of patients with pre-operative flexion less than 120° in both knees. Thus, the ideal candidate for the high flexion device may be one with lesser pre-operative flexion.