A hybrid neuroprosthesis can significantly reduce upper limb loading and the amount of muscle stimulation for walking in patients with paraplegia, potentially enabling walking for longer distances and with less effort than with either bracing or functional neuromuscular stimulation alone, according to a recent study.
A man with a spinal cord injury had percutaneous intramuscular electrodes implanted near nerves innervating most major muscles controlling the hips, knees and ankle. To provide knee stability during stance and foot-ground clearance during swing while minimizing knee extensor stimulation, a hydraulic stance control knee hybrid neuroprosthesis (HNP) was combined with a sensor-based functional neuromuscular stimulation (FNS) controller. A stance control knee mechanism (SCKM) supported the user during stance and constrained the knee in extension while the FNS controller deactivated stimulation to the knee extensor muscles. Researchers used this HNP to examine the feasibility of reducing both the upper loading applied to a walking aid and muscle stimulation duty cycle and compared the results with walking with either isocentric reciprocal gait orthosis (IRGO) or FNS alone.
Overall, the HNP reduced the average vertical upper limb forces on the walking aid by 36% vs. walking with FNS only. The HNP also reduced average vertical upper limb forces on the walking aid by 17% vs. IRGO. Average forward trunk lean was 16° greater with FNS vs. HNP. Of the preprogrammed baseline levels used in FNS-only walking, The HNP reduced the stimulation duty cycle of the knee extensor muscles by 68%, according to the researchers, and there was minimal effect on knee angle trajectory during swing from the additional mass and internal friction of the SCKM.
For More Information:
To CS, Kobetic R, Bulea TC, et al. Sensor-based stance control with orthosis and functional neuromuscular stimulation for walking after spinal cord injury. J ProsthetOrthot. 2012;24:124-132.
Disclosure: The researchers have no relevant financial disclosures.