Long-term crutch users utilize Lofstrand crutches for locomotion commonly using swing-through or reciprocal gait patterns. Repetitive high forces, hyperextension and ulnar deviation of the wrist, and excessive palmar pressure compressing the median nerve associated with crutch walking have reported to cause discomfort, joint pain, wrist strain, carpal tunnel syndrome and other serious injuries. To address these issues, we developed the pneumatic ergonomic crutches (PEC) that consisted of a pneumatic sleeve orthosis, an energy harvesting system and an energy storage system. The pneumatic sleeve orthosis utilized a soft pneumatic actuator, called fiber-reinforced elastomeric enclosure, coiled around the forearm and secured to the cuff. In the first study, sleeve orthosis performance was examined. Human subject testing indicated significantly improved wrist posture, increased loading sharing to the cuff, reduced and redirected palmar pressure while using the orthosis. In the second study, the fully-developed PEC was presented. The PEC utilized an energy harvesting piston pump to collect pneumatic energy during crutch gait. The collected pneumatic energy was stored into a pneumatic elastomeric accumulator (PEA) inside the crutch shaft, which can be used to inflate the sleeve orthosis to make a self-contained crutch system. We optimized dimensions and specifications of the piston pump and the PEA to minimize the number of gait cycles used to charge the PEA to a target pressure that can be used to fully charge the sleeve orthosis. Bench-top testing was conducted on the PEC and demonstrated the ability of charging the sleeve orthosis using air stored in the PEA after 38 gait cycles. Protocols for future human subject testing to evaluate the system performance of the PEC were also presented.
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