gms | German Medical Science

Objectives: Medial open-wedge high tibial osteotomy (OWHTO) is a widely used treatment option in patients with varus malalignment and early medial osteoarthritis of the knee. However, overall understanding of the effect of corrective osteotomy on joint kinematics and joint contact mechanics remains inadequate, and further research in this field is essential for predicting surgical outcomes. Therefore, the aim of this study was to investigate the relationship between OWHTO of various degrees of coronal correction and biomechanics of the knee joint using a multi-body simulation model.

Methods: OWHTO with an open tibial wedge of 6 mm to 12 mm (at 1 mm intervals) was virtually performed on each of eight three-dimensional CAD-models derived from CT-scans of full-leg cadaver specimens (Figure 1 [Fig. 1]).

A multi-body simulation model of the native knee was derived based on an existing force- and kinematic-validated model of TKA [1]. Relevant modifications such as adjusting the pressure module to model the contact mechanics of the native knee surfaces, or the inclusion of the ACL were performed. For each patient and each OWHTO version, an individual biomechanical simulation model was built, based on the surface models provided. With each model, a knee bend from 10° to 90° of knee flexion was simulated.

Tibio- and patellofemoral kinematics were derived and deviations from the kinematics of the "preop" model were calculated. Mean values of those deviations were calculated for each kinematic parameter and each OWHTO version to determine which parameters are most affected by OWHTO.

Results and conclusion: A total of five tibiofemoral and five patellofemoral kinematic parameters were evaluated for each OWHTO simulated (Table 1 [Tab. 1]). Of all parameters assessed, an increase in the degree of coronal osteotomy had the greatest effect on tibiofemoral internal-external rotation. A decrease in the degree of tibial internal rotation during knee flexion of approximately 0.5° was observed for each 1-mm increase in coronal correction.

In addition, an increase in the degree of coronal osteotomy resulted in abnormal medial translation of the tibia.

Of all the patellofemoral parameters studied, an increase in the degree of osteotomy showed the greatest effect on mediolateral translation and the tilt of the patella to the lateral side.

The simulation of different degrees of OWHTO showed a multidirectional influence on joint kinematics, which may affect joint stability and contact pressure. Improving multibody simulation models for the OWHTO may increase the understanding of the multidirectional effects of surgical intervention and thus improve the predictability of surgical outcomes.