Biomechanical and metabolic performance of a new orthotic knee joint principle for stance phase safety

Abstract

Fig. 2. Changes in inclination angle associated with peak joint reaction forces during stance with increasing NSA. UM is the reference undeformed model. ing a decrease in the peak mediolateral component with increasing NSA. A distinct trend to increased peak vertical joint reaction forces with increased NSA was found. As a result, the inclination angle of the resultant reaction force in the frontal plane decreased substantially with decreasing NSA, introducing a more vertical alignment of the reaction force at peak loading (Fig. 2). Although, the sagittal plane angle showed variations in the individual model, no clear relation with the changes in NSA could be established. When halving the abductor muscle force generating capacity, all components of the reaction forces decreased. However, the previously described relations of the joint reaction forces with NSA were unchanged. 6. Discussion The interaction between hip geometry, muscle moment generating capacity and hip loading can be analyzed using inverse dynamics based on personalized musculoskeletal modeling. Our results show an important interaction between NSA and mediolateral reaction forces, causing a more vertical inclination angle in the frontal plane during gait. This therefore will result in a more vertical loading of the implant when peak reaction forces are applied during gait. Although we did not analyze the interaction between NSA, NL and PW, our findings do suggest that a minimal NSA angle needs to be preserved in order to limit the mediolateral force component and limit the resulting bending stress in the femoral shaft. The calculation of individual hip loading by use of musculoskeletal modeling and inverse analysis may contribute to understanding the effect of hip joint loading on bone remodeling and implant load shearing.