Abstract-Implanted functional electrical stimulation (FES) systems for walking are experimentally available to individuals with incomplete spinal cord injury (SCI); however, data on short-term therapeutic and functional outcomes are limited. The goal of this study was to quantify therapeutic and functional effects of an implanted FES system for walking after incomplete cervical SCI. After robotic-assisted treadmill training and overground gait training maximized his voluntary function, an individual with incomplete SCI (American Spinal Injury Association grade C, cervical level 6-7) who could stand volitionally but not step was surgically implanted with an 8-channel receiver stimulator and intramuscular electrodes. Electrodes were implanted bilaterally, recruiting iliopsoas, vastus intermedius and lateralis, tensor fasciae latae, tibialis anterior, and peroneus longus muscles. Twelve weeks of training followed limited activity post-surgery. Customized stimulation patterns addressed gait deficits via an external control unit. The system was well-tolerated and reliable. After the 12-week training, maximal walking distance increased (from 14 m to 309 m), maximal walking speed was 10 times greater (from 0.02 m/s to 0.20 m/s), and physiological cost index was 5 times less (from 44.4 beats/m to 8.6 beats/m). Voluntary locomotor function was unchanged. The implanted FES system was welltolerated, reliable, and supplemented function, allowing the participant limited community ambulation. Physiological effort decreased and maximal walking distance increased dramatically over 12 weeks.

This study describes the preliminary performance of an implanted neuroprosthesis for standing and transfers after spinal cord injury. The system is a 16-channel version of the 8-channel Case Western Reserve University/Veteran Affairs (CWRU/VA) standing/transfer neural prosthesis. It includes bilateral four channel femoral nerve cuff electrodes for stimulation of the vastii to provide knee extension. To date, the prosthesis has been implanted in one subject who was previously a user of the original 8-channel CWRU/VA system. In the first four months after implantation of the new neuroprosthesis, this subject has been able to stand for approximately 2.5 minutes with up to 86% of total body weight supported by the lower extremities. These values far exceed the stand time (approximately 1 minute) and body weight distributions (55% on the legs) for the same subject when using the 8-channel system four months after implantation. The nerve cuff electrodes have been stable over the four months since implantation, with little change in stimulation threshold and saturation values, which suggests that there have been no biological effects on the electrodes. These results suggest that the second generation 16-channel neuroprosthesis with nerve-cuff electrodes will provide stronger knee extension moments over a longer duration before fatigue during standing and transfers.

No abstract

This study describes the preliminary performance of an implanted neuroprosthesis for standing and transfers after spinal cord injury. The system is a 16-channel version of the 8-channel Case Western Reserve University/Veteran Affairs (CWRU/VA) standing/transfer neural prosthesis. It includes bilateral four channel femoral nerve cuff electrodes for stimulation of the vastii to provide knee extension. To date, the prosthesis has been implanted in one subject who was previously a user of the original 8-channel CWRU/VA system. In the first four months after implantation of the new neuroprosthesis, this subject has been able to stand for approximately 2.5 minutes with up to 86% of total body weight supported by the lower extremities. These values far exceed the stand time (approximately 1 minute) and body weight distributions (55% on the legs) for the same subject when using the 8-channel system four months after implantation. The nerve cuff electrodes have been stable over the four months since implantation, with little change in stimulation threshold and saturation values, which suggests that there have been no biological effects on the electrodes. These results suggest that the second generation 16-channel neuroprosthesis with nervecuff electrodes will provide stronger knee extension moments over a longer duration before fatigue during standing and transfers.