Forward stair descent with hybrid neuroprosthesis after paralysis: Singlecase study demonstrating feasibility

摘要

The ability to negotiate stairs is important for communityaccess and independent mobility but requires moreeffort and strength than level walking. For this reason, previousattempts to utilize functional neuromuscular stimulation (FNS)to restore stair navigation after spinal cord injury (SCI) havehad limited success and are not readily generalizable. Stairdescent is particularly challenging because it requires energyabsorption via eccentric muscle contractions, a task not easilyaccomplished with FNS. This article presents the design andinitial testing of a hybrid neuroprosthesis with a variableimpedance knee mechanism (VIKMHNP) for stair descent.Using a 16channel percutaneous FNS system, a muscle activationpattern was synthesized to descend stairs with the VIKMHNPin a stepbystep fashion. A finite state control systemwas implemented to deactivate knee extensor stimulation andutilize the VIKMHNP to absorb energy and regulate descentspeed. Feasibility testing was performed on one individualwith complete thoraciclevel SCI. Stair descent was achievedwith maximum upperlimb forces of less than 45% bodyweight compared with previously reported value of 70% withFNS only. The experiments also provided insight into designrequirements for future hybrid systems for stair navigation, theimplications of which are discussed.