Standing after spinal cord injury with four-contact nerve-cuff electrodes for quadriceps stimulation

Abstract

This paper describes the performance of a 16-channel implanted neuroprosthesis for standing and transfers after spinal cord injury including four-contact nerve-cuff electrodes stimulating the femoral nerve for knee extension. Responses of the nerve-cuffs were stable and standing times increased by 600% over time-matched values with a similar eight-channel neuroprosthesis utilizing muscle-based electrodes on vastus lateralis for knee extension.

Figures

Fig. 1

(a) The IST-16 stimulator which was implanted in a subject with SCI to restore standing function. (b) A self-sizing four-contact spiral nerve-cuff electrode used on bilateral femoral nerves in this study to stimulate the quadriceps muscles for knee extension. (c) The unspiraled nerve-cuff. All four contacts and the lead wire are visible.

Fig. 2

Average threshold charge injected and standard deviation on all four contacts of both right and left nerve-cuff electrodes.

Fig. 3

Peak isokinetic extension moment for left and right knees at 16 weeks post-implantation. Averaged data and standard deviations are shown for epimysial electrodes on VL in the IRS-8 system as well as for nerve-cuff electrodes on the femoral nerve in the IST-16 system. Data for individual and combinations of nerve-cuff contacts that isolated the vasti are shown.

Fig. 4

(a) Maximum standing time and (b) %BW on the legs at 16, 40, and 72 weeks post-implantation. Data are shown for the IRS-8 system, the complete IST-16 system, and the IST-16 system without stimulation of the POST-ADDs. Maximal values achieved with the epimysial IRS-8 system are presented for comparison. %BW data for 40 and 72 weeks post-implantation with the IRS-8 system (*) were unavailable.