Patient Motion Using a Computerized Leg Brace in Everyday Locomotion Tasks

Exoskeletal systems are becoming a rehabilitation standard of care for persons with lower limb paralysis. As muscular dysfunctions affect a heterogeneous patient group, each individual develops their own strategy to negotiate everyday locomotion challenges. This paper introduces a microprocessor controlled orthotic system that passively supports people with lower limb paralyses in their everyday locomotion tasks while incorporating the user as the highest control entity. A clinical study with seven patients with a range of leg pareses investigated the functionality and usage of the system while capturing the mechanical stress on the device. Data from the knee joint was recorded in locomotion tasks including level walking, ramp, and stair negotiation. For all patients, the measurements demonstrate that the motion for level walking was close to the motion of healthy individuals. In other tasks, variations between the patients were large with respect to motion kinematics, power, and torque requirements. As the control concept supported individualized motion patterns, patients perceived the system functionality as intuitive. The mechanically most demanding task was stair descent with a peak torque of 1.47 Nm/kg and peak dissipative power up to 2.67 W/kg. Intra-subject variability makes prediction of movements and loads challenging.