A valid novel ground reaction force distribution algorithm to determine midfoot kinetics of gait with a single force plate

Understanding midfoot joint kinetics is valuable for improved treatment of foot pathologies. Segmental foot kinetics cannot currently be obtained in a standard gait lab without the use of multiple force plates or a pedobarographic plate overlaid with a force plate due to the single ground reaction force (GRF) vector. Can an algorithm be created to distribute the GRF into multiple segmental vectors that will allow for calculation of accurate midfoot and ankle moments? 20 pediatric subjects (10 typically developing, 10 with foot pathology) underwent multi-segment foot gait analysis using the Milwaukee Foot Model. A novel force distribution algorithm (FDA) was developed to proportionally divide the GRF into segmental vectors based on the location of the center of pressure and these vectors were used to calculate midfoot and ankle moments with an inverse dynamic approach. FDA GRF segmental vectors and midfoot/ankle moments were compared to metrics obtained from a previously validated pedobarographic plate methodology using correlations, statistical parametric mapping, and effect size with 95 % confidence intervals. All force distributions and midfoot/ankle moments waveforms were highly correlated with R> 0.99 for hindfoot and forefoot forces, R> 0.99 for sagittal and transverse plane moments, and R> 0.95 for coronal plane moments. No statistical differences were found during 2nd rocker where the FDA was applied. Midfoot and ankle moments can be accurately obtained with our algorithm using standard equipment utilized in clinical and research motion analysis labs without the requirement of additional trials, or targeted walking by patients. •Ground reaction force is split into separate vectors for a multi-segment foot model.•Accurate midfoot moment are calculated with a novel force algorithm.•Algorithm is effective for typical and pathologic pediatric gait.