Plantar pressure based estimates of foot kinematics during gait – A least squares optimization approach

Nowadays, the use of plantar pressure measurement systems to evaluate foot and ankle pathologies is well established in clinical practice. Although relevant to detect local tissue overloading, to date, plantar pressure data cannot be used to evaluate ankle-foot kinematics. We hypothesized that it is possible to enhance the possibilities of plantar pressure evaluation to compute ankle-foot kinematics, thereby increasing its potential to assess pathologies and evaluate treatments. We developed an algorithm to estimate ankle-foot kinematics based on plantar pressure data and the trajectories of only five markers. The algorithm is based on a least squares optimization approach that minimizes the weighted difference between simulated and measured plantar pressure and marker data. Marker positions and plantar pressures are simulated in OpenSim using an extended musculoskeletal shank and foot model with six bodies and fourteen degrees of freedom coupled with an ellipsoid based elastic foundation contact model (EFM). The estimated foot kinematics are similar to kinematics calculated from trajectories of an extended marker set (the average root mean square difference between both methods is 3.2o). The here presented approach, however, requires less preparation time only favoring its use in clinical practice.status: publishe