Effects of high tibia osteotomy on knee ligamentous forces during gait: A finite element study

It is generally accepted that the high tibial osteotomy (HTO) improves the stress distribution on the articular cartilage of varus knees in the standing posture. The effects of HTO during dynamic activities, e.g., gait, however, is unclear considering the fact that it also affects the tensions of the knee ligaments and hence the knee configuration under external load and knee flexion. In this study, the HTO was simulated on a detailed 3D model of the knee consisting of femur, tibia, cartilage layer, menisci, and four ligaments. The geometry of the model was acquired from the CT and MRI data of a volunteer and the mechanical properties of the model components were obtained from the literature. In total, 42 simulations were conducted in ABAQUS to observe the effects of the correction angle and the posterior tibial slope on the tensions of the ligaments. Results indicated that the ACL tension is highly affected by both the correction angle and the posterior slope. The ACL force was minimal with the optimal wedge-angle and a small slope. LCL force decreased significantly following HTO, but showed a slight increase for smaller slopes. The PCL force, on the other hand, increased slightly following HTO and with smaller posterior slopes. It was concluded that the most important effect of the HTO and posterior slope on the knee ligaments is that of the ACL. Care should be taken to perform the surgery with optimum correction angle, to pass the mechanical axis through the center of the knee joint, and at the same time keep the posterior slope sufficiently small, beyond 10 degrees.