Foot model for clinical application

Several multisegment foot models to measure the motion of intrinsic joints of the foot have been reported. Use of these models in clinical decision making is limited due to lack of variability measures and untested adaptability for pathologic subjects and multiple data-collection sites. Therefore, a new clinical foot model was developed to reduce the variability associated with foot models due to marker placement error. Kinetics of foot models have not been developed in previous foot models due to difficulty in measuring ground reaction forces in multiple parts of the foot. Therefore, a strategy for segmenting ground reaction force by use of a synchronized pressure plate coupled with a dimensionally matched force plate was developed.;Several musculoskeletal models exist for full-body gait analysis but these treat the foot as a single segment and ignore the motion of intrinsic joints. To date, no multi-segment kinematic foot model has been used as part of a musculoskeletal model. We hypothesize that a multisegment foot model can be constructed, scaled to match a subject and driven with subject data from an existing kinematic model to estimate internal muscle activation patterns. A three-segment musculoskeletal model for the right foot was developed. Model geometry was optimized with moment arm measured from cadaver testing. The model was driven by kinematic and kinetic gait data from 5 normal pediatric subjects and muscle activation levels required to produce joint motions were calculated using an inverse dynamic analysis approach. To evaluate the model outcomes, the computed muscle activation patterns were compared with measured electromyography (EMG) activation patterns reported in the literature.;Model application was carried out on typically developing and pathologic (planovalgus foot) pediatric subjects at two data collection sites. Intraclinician and interclinician variability in model outcomes (joint angles, moments and power during walking) have been quantified for both control and pathologic groups. Model outcomes were compared between the two groups to demonstrate the capability of reflecting differences between normal and impaired foot function.