Loads on the prosthesis-socket interface of above-knee amputees during normal gait: validation of a multi-body simulation.

The treatment of above-knee amputees with a prosthesis based on a socket is currently considered the standard clinical treatment. Nevertheless there are few investigations on mechanical loading conditions on these devices under realistic circumstances. Further insight in this matter might improve the design of sockets for everyday application. The presented study investigates the loads acting on the socket-interface with a multi-body simulation (MBS). Aim of this study is to validate the quality of the applied MBS next to a direct measurement device. Therefore a custom strain gauge based force-moment sensor is integrated into the conventional socket-based prosthesis of six above-knee amputees. Each subject performs level-walking with kinematic and kinetic data being recorded in a gait laboratory. The data of the marker trajectories is processed in an inverse dynamics MBS where loads at the location of the sensor are determined. The comparison of both methods shows a good agreement of forces and moments and the simulation can be considered fully validated. RMSD is 4.7%BW for the forces and 27.0%BWM for the moments. The model will be used in further research to determine loads on the socket-prosthesis interface of above-knee amputees especially in high risk situations such as falling scenarios, where direct measurement with amputees is not possible for ethical reasons.