Article

The ability to negotiate stairs is important for community access and independent
mobility but requires more effort and strength than level walking. For this
reason, previous attempts to utilize functional neuromuscular stimulation (FNS)
to restore stair navigation after spinal cord injury (SCI) have had limited
success and are not readily generalizable. Stair descent is particularly
challenging because it requires energy absorption via eccentric muscle
contractions, a task not easily accomplished with FNS.
This article presents the
design and initial testing of a hybrid neuroprosthesis with a variable impedance
knee mechanism (VIKM-HNP) for stair descent. Using a 16-channel percutaneous FNS
system, a muscle activation pattern was synthesized to descend stairs with the
VIKM-HNP in a step-by-step fashion. A finite state control system was implemented
to deactivate knee extensor stimulation and utilize the VIKM-HNP to absorb energy
and regulate descent speed. Feasibility testing was performed on one individual
with complete thoracic-level SCI. Stair descent was achieved with maximum
upper-limb forces of less than 45% body weight compared with previously reported
value of 70% with FNS only. The experiments also provided insight into design
requirements for future hybrid systems for stair navigation, the implications of
which are discussed.

Langue : ANGLAIS