(Seungbum Koo, Associate Professor, Chung-Ang University, Seoul, South Korea, 02. May, 2016 )
THE WINNER IN THE 2015 SIXTH GRAND CHALLENGE COMPETITION TO PREDICT IN VIVO KNEE LOADS. There can be many different ways to predict in vivo knee contact force. In our study multiple reaction elements were placed on the contact surface of a joint and used the inverse-dynamics-based optimization in AnyBody Modeling System to calculate the distribution of intra-articular contact forces for the Sixth Grand Challenge Competition to Predict in vivo Knee Loads. Previously, we used the same principle to predict ground reaction force including shear force during walking. In the knee the joint constraint and marker placements on the model seemed very important to predict accurate knee kinematics and the resulting knee contact force. A knee contact model was developed to include 32 reaction elements on the surface of a tibial insert of a total knee replacement, which was embedded in the AnyBody MOCAP model. A knee contact model with a hinge joint and normal alignment could predict knee contact forces with root mean square errors (RMSEs) of 165N and 288N for the medial and lateral portions of the knee, respectively, and coefficients of determination (R^2) of 0.70 and 0.63. When the hinge joint was replaced with ball-socket joint and locations of leg markers were adjusted to account for the valgus lower-limb alignment of the subject, RMSE values improved to 144N and 179 N, and R^2 values improved to 0.77 and 0.37, respectively.
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