The Effect of Crutch Gait Pattern on Shoulder Reaction Force when Walking with Lower Limb Exoskeletons.

Lower limb exoskeleton robots have shown great potential in assistive and rehabilitative applications, allowing individuals with motor impairment, such as spinal cord injury (SCI) patients, to perform overground gait. Most assistive lower limb exoskeletons require users to use crutches to balance themselves during standing and walking. However, long-term crutch usage has been demonstrated to be potentially harmful to the shoulder joints, due to the repetitive high shoulder reaction forces. Investigations into the shoulder loads experienced during exoskeleton use are needed to understand the extent of this harm and, if required, to reduce the risk of injury. In this preliminary study, the effects of different gait patterns on the shoulder load are investigated in an experiment involving three able-bodied individuals. Specifically, the differences in shoulder load during exoskeleton walking are studied with two commonlyobserved gait patterns: (1) the four-point parallel crutch gait and (2) the four-point reciprocal crutch gait. Contact forces between the ground and the human-exoskeleton system were recorded and used to indicate shoulder reaction force. The results suggested no significant differences in maximum force and maximum rate of loading between the two crutch gait patterns, and only minor differences in force time integral. This indicates that shoulder reaction force may not be a significant factor when choosing between crutch gaits during exoskeleton use.