Clinical Applicability of an Existing Proportionality Scheme in Three-Segment Kinetic Foot Models

An important methodological challenge in multi-segment kinetic foot models is to partition the total ground reaction force across different foot segments. Several studies applied a proportionality scheme based on the combination of a pressure- and force platform. A recent study highlighted distinct errors in the partitioning of shear forces when using this proportionality scheme. To date, the impact of this shear force partitioning error analysis on joint moment calculations using inverse dynamic calculations in pathological gait is not known. Hence, the goal of this study was to investigate the clinical applicability of an existing proportionality scheme by extending the shear force partitioning error analysis towards joint moment calculations. Both healthy (n = 10) and pathological gait (n = 10) was assessed using (I) an adjacent force plate method and (II) the estimation method based on an existing proportionality scheme. A correction factor matrix was developed to compensate for the shear force partitioning errors in the estimation method. Extending the shear force partitioning error analysis towards joint moments using inverse dynamic calculations, did not reveal significant differences when comparing corrected joint moments with the estimated joint moments in both healthy and pathological gait.