Pressure changes under the ischial tuberosities during gluteal neuromuscular stimulation in spinal cord injury: a comparison of sacral nerve root stimulation with surface functional electrical stimulation.

Abstract

To compare the magnitude of interface pressure changes during gluteal maximus contraction by stimulating sacral nerve roots with surface electrical stimulations in patients with spinal cord injuries (SCIs). Pilot interventional study. Spinal injury research laboratory. Adults (N=18) with suprasacral complete SCI. Sacral nerve root stimulation (SNRS) via a functional magnetic stimulator (FMS) or a sacral anterior root stimulator (SARS) implant; and surface functional electrical stimulation (FES). Interface pressure under the ischial tuberosity (IT) defined as peak pressure, gradient at peak pressure, and average pressure. With optimal FMS, a 29% average reduction of IT peak pressure was achieved during FMS (mean ± SD: 160.1±24.3mmHg at rest vs 114.7±18.0mmHg during FMS, t5=6.3, P=.002). A 30% average reduction of peak pressure during stimulation via an SARS implant (143.2±31.7mmHg at rest vs 98.5±21.5mmHg during SARS, t5=4.4, P=.007) and a 22% average decrease of IT peak pressure during FES stimulation (153.7±34.8mmHg at rest vs 120.5±26.1mmHg during FES, t5=5.3, P=.003) were obtained. In 4 participants who completed both the FMS and FES studies, the percentage of peak pressure reduction with FMS was slightly greater than with FES (mean difference, 7.8%; 95% confidence interval, 1.6%-14.0; P=.04). SNRS or surface FES can induce sufficient gluteus maximus contraction and significantly reduce ischial pressure. SNRS via an SARS implant may be more convenient and efficient for frequently activating the gluteus maximus.