Kinematic comparison of walking on uneven ground using powered and unpowered prostheses

Recent research has focused on the design of intelligent prosthetic ankle devices with the goal of adapting behavior of the device to accommodate all walking surfaces that an individual encounters in daily life. To date, no studies have looked at how such devices perform on uneven terrain.

11 young adults with unilateral transtibial amputation participated in two data collection sessions spaced approximately 3 weeks apart. In each session they walked across a loose rock surface at three controlled speeds. In the first session, they wore a passive, energy storage and return prosthesis and in the second, they wore a powered prosthesis (BiOM, iWalk, Bedford, MA, USA).

Subjects had a 10% faster self-selected walking speed when wearing the powered (1.16 m/s) compared to unpowered prosthesis (1.05 m/s; p=0.031). They walked with increased ankle plantarflexion on their prosthetic limb throughout the gait cycle when wearing the powered compared to unpowered prosthesis. This was especially evident in the increased plantarflexion during push-off (p<0.001). There was a small (<3°), but statistically significant decrease in knee flexion during early stance when wearing the powered device (p=0.045). Otherwise, the kinematics of the knee and hip were nearly identical when wearing the different devices. Subjects had decreased medial-lateral motion of their center of mass when wearing the powered prosthesis (p=0.020), but there were no differences in medial-lateral margins of stability between the devices (p=0.662).

Subjects did not significantly alter their proximal joint kinematics on this irregular surface as a result of the addition of power.