Preventing ischial pressure ulcers: III. clinical pilot study of chronic neuromuscular electrical stimulation

Abstract

Objective: BIONs™ BIOnic Neurons are injectable, wireless microstimulators that make chronic BION Active Seating BAS possible for pressure ulcer prevention PUP. Neuromuscular electrical stimulation NMES produces skeletal motion and activates trophic factors, counteracting three major etiological mechanisms leading to pressure ulcers PUs: immobility, soft-tissue atrophy, and ischemia. Companion papers I and II reviewed prior experience with NMES for PUP, and analyzed the biomechanical considerations, respectively. This paper presents a treatment strategy derived from this analysis, and the clinical results of the first three cases. Methods: Two BIONs implanted one on inferior gluteal nerve to gluteus maximus GM, and other on sciatic nerve to hamstrings HS, in 3 spinal cord injured SCI subjects already undergoing gluteal rotation flaps for PUs. BAS using HS when seated, and BION Conditioning BC via GM+HS when non-weightbearing. Follow-up: 1 yr, including 6 mo. treatment window interface pressure mapping; muscle perfusion scans; MRI, X-ray volume assessments. Results: Successfully implanted and activated both desired muscle groups, selectively, in all. No PU recurrences or wound complications. Two subjects completed protocol. Mean results: Interface: contact pressure -10%; maximum pressure -20%; peak pressure area -15%. Vascularity: GM +20%, HS +110%. Perfusion: GM +70%, HS +440%. Muscle volume: GM +14%, HS +31%. Buttock soft-tissue padding: +49%. 1 BION failed; 1 BION rotated under GM. Conclusions: Promising proof-of-concept data supporting the feasibility of implanted microstimulators to achieve sufficiently strong and selective activation of target muscles for PUP. Ultimate goal is prophylactic deployment through bilateral, nonsurgical injection of BIONs in chronically immobile patients.