Increased kinematic changes in ascending compared with descending biplanar cut in open wedge high tibial osteotomy-a multibody simulation

The ascending or descending extended biplanar tibial cut in open wedge high tibial osteotomy (owHTO) not only changes the lower limb anatomy in the coronal plane but also leads to different three-dimensional (3D) changes in the patellofemoral joint. This study aimed to perform a comprehensive analysis of the dynamic biomechanical changes in the knee joint using a multibody simulation model. Thirteen 3D computer models derived from lower limb computer tomography scans were used for owHTO. Osteotomies with ascending or descending biplanar cut were simulated for each wedge height from 6 to 12 mm (in 1-mm intervals). Multibody simulation was used to analyze differences in patellar shift, patellar tilt, mediolateral patellar rotation, and tibiofemoral rotation during a squat simulation from 5° to 100° knee flexion. The main effects of an ascending compared with a descending extended biplanar cut in owHTO were characterized by an increase in lateralization of the patella and rotation, along with reduced tilt. Linear mixed models revealed statistically significant effects of both wedge height and cut variant on knee kinematics at 100° knee flexion, with the influence of the cut variant (ascending/descending) being higher on all analyzed kinematic parameters. Significant differences in the changes in patellofemoral shift, tilt, rotation, and tibiofemoral rotation were observed when performing owHTO with an ascending versus a descending biplanar cut. Apart from tibiofemoral rotation, the resulting kinematic changes were greater with an ascending cut.