Development of hybrid orthosis for standing, walking, and stair climbing after spinal cord injury.

This study explores the feasibility of a hybrid system of exoskeletal bracing and multichannel functional electrical stimulation (FES) to facilitate standing, walking, and stair climbing after spinal cord injury (SCI). The orthotic components consist of electromechanical joints that lock and unlock automatically to provide upright stability and free movement powered by FES. Preliminary results from a prototype device on nondisabled and SCI volunteers are presented. A novel variable coupling hip-reciprocating mechanism either acts as a standard reciprocating gait orthosis or allows each hip to independently lock or rotate freely. Rotary actuators at each hip are configured in a closed hydraulic circuit and regulated by a finite state postural controller based on real-time sensor information. The knee mechanism locks during stance to prevent collapse and unlocks during swing, while the ankle is constrained to move in the sagittal plane under FES-only control. The trunk is fixed in a rigid corset, and new ankle and trunk mechanisms are under development. Because the exoskeletal control mechanisms were built from off-the-shelf components, weight and cosmesis specifications for clinical use have not been met, although the power requirements are low enough to provide more than 4 hours of continuous operation with standard camcorder batteries.

Development of a hybrid gait orthosis: a case report.

OBJECTIVE: The purpose of this case study was to improve stability, posture, and speed of gait in an individual with paraplegia through the application of a hybrid system including trunk-hip-knee-ankle-foot orthosis (THKAFO) with lockable joints and multichannel functional electrical stimulation (FES) with implanted electrodes. METHODS: Two hybrid orthoses were implemented and evaluated on a person with complete absence of motor function and sensation below the T-9 level spinal cord injury. The first hybrid was a modified isocentric reciprocal gait orthosis (IRGO) with the knees controlled by FES, the ankles fixed at neutral, and the hips coupled with a reciprocator. The second hybrid had a THKAFO instrumented with lockable joints using wrap-spring clutches at the hips and knees (THKAFO-LJ) that provided free extension and allowed for flexion only when disengaged by solenoids. A microprocessor-controlled stimulator provided muscle stimulation and activation signals for the solenoids. These two hybrid systems were compared with an FES-only system. RESULTS: The IRGO hybrid system with the hip reciprocator engaged provided a stable gait with erect posture with minimal anterior trunk lean using only quad canes for support. However, the walking speed was slow, due to limited step length imposed by the reciprocator. The walking speed with the THKAFO-LJ hybrid system was significantly faster than that with the IRGO hybrid with the reciprocator engaged, and was comparable with the FES-only gait; however, it resulted in excessive anterior trunk lean. A walker with 2 wheels was required to maintain balance. CONCLUSION: The results point to the need for a hybrid system that allows for unencumbered hip and knee joint motion for stepping without excessive anterior trunk lean. Such a hybrid system could provide a reasonable speed in gait powered by muscle stimulation, without the usual joint motion constraints imposed by the bracing, while providing stability that is normally seen only with bracing. Further advantages would include reduction in required stimulation during standing and support phases of gait.