Foot bone kinematics at half and three quarters body weight: A robotic cadaveric simulation of stance phase

Lower limb cadaveric robotic gait simulators have been employed to model foot bone kinematics during the stance phase of gait. Often the simulations are performed at reduced body weight (BW) but the effect of this limitation on foot bone kinematics has not been quantified. In this study we utilized the robotic gait simulator (RGS) to measure in vitro foot bone kinematics at different applied ground reaction forces (GRFs) (50% BW and 75% BW). The RGS simulated gait by replicating in vivo tibial kinematics, GRFs, and tendon forces. A six-camera motion analysis system recorded the in vitro motion of ten bones in the foot. Linear mixed effects regression was used to test for differences in range of motion (ROM) by BW (75% vs. 50%) for 12 bone-to-bone relationships. Statistically significantly (p <; 0.05) differences in ROM by BW were found for six of the 12 angles investigated. On average the ROM for the 75% BW simulations were systematically higher than that for the 50% BW simulations (p <; .0001), but the magnitude of the difference was small (1.2°). These results indicate that reduced BW in vitro simulations approximately model the ROM and temporal characteristic of foot bone kinematics.