Validation of the hip contact force for a novel lower extremity muscloskeletal model

To analyze for osteoarthritis patients, it is considered clinically useful to predict biological force by the lower extremity musculoskeletal model. Recently years, many more detailed musculoskeletal models have been developed. However, most of them are constructed by straight muscles (Via-Point muscle), and the number of lower extremity models that reproduce actual muscle path is few. In this study, we developed the lower extremity musculoskeletal model which reproduced the actual muscle path and validated the accuracy by using motion analysis data. First, we constructed to connect the origin and insertion point of lower extremity muscles determined from the anatomical book on a bone model constructed from lower extremity musculoskeletal model data set provided by Anybody Modeling System Via-Point muscle. After that, we constructed a Wrapping muscle that reproduces the curvilinear shape of the muscle by putting the Via-Point muscle along multiple ellipsoids. Secondly, we conducted the inverse dynamics analysis using motion analysis data to validate the accuracy of the developed model. For the verification, we used the walking data of Total Hip Arthroplasty patient and the hip contact force (HCF) provided by the OrthoLoad. Reflecting these data in the developed model, we conducted the inverse dynamics analysis to calculate the anterior-posterior, medial-lateral, and proximal-distal components of the HCF. We calculated the mean squared error (RMSE) of the predicted value (HCF
_Predicted
) and the actual value (HCF
_Measured
) for the HCF calculated by resulting the three axial direction components. As well as, we also calculated RMSE of the default model to compare the developed model. As a result, the RMSE of HCF
_Measured
and HCF
_Predicted
was 0.208 * BW for HCF
_Measured
. In addition, the RMSE of HCF Predicted calculated with the default model provided by AMS is 0.359 * BW, which showed to reduce the error by 40%. Based on the results of this study, it was possible to develop a model with higher accuracy than in the past by reconsidering the origin and insertion of the muscle path into a shape closer to that of the actual body.