Sacral Nerve Stimulation : The Effect on Gluteal Tissues in Spinal Cord Injury

Following a spinal cord injury (SCI), up to 85% of individuals develop pressure ulcers (PUs) at some point during their lifetime. Tissue ischemia caused by prolonged localized pressures combined with loss of sensation below the level of injury have been considered the major factors for PUs in SCI. Ischial tuberosities are one of the most common sites of PUs in SCI individuals who use wheelchairs. PUs represent a very significant cost burden for the health and social care system and are extremly difficult to fully repair. Hence, prevention of PUs has been the priority. Specialised cushions to reduce seating pressures combined with pressure relief by the patient perfonning 'push-ups' or 'leaning forward' are presently considered the best options for preventing ischial PUs in SCI population. However, perfonning pressure relief requires good upper limb strength together with continued motivation; which may not always be present in high-level lesion individuals. Furthennore, seat cushions alone do not pennit adequate pressure relief for continuous sitting. The idea of activating paralyzed gluteal muscles through_tl1~~s~ of functional electrical stimulation (FES),has been explored over the past two decades for use in SCI. However, surface FES stimulates the muscles by repeatedly applying large electrodes to the buttocks. The long-tenn practicality and patient compliance with this technique is a problem. It was reported that non-invasive Functional Magnetic Stimulation (FMS) of the sacral nerve roots can activate gluteal muscles. In this thesis, Sacral Anterior Root Stimulator (SARS) implant (currently used for bladderlbowel empty in SCI) is proposed for ischial pressure ulcer prevention in SCI population. The aims of this study are 1)' To investigate the dynamic effects of sacral FMS on seating interface pressure changes in able bodied subjects; and evaluate the efficacy of sacral FMS; 2) To investigate the dynamic effects of sacral FMS on seating interface pressure and cutaneous hemoglobin and oxygenation changes in SCI; and demonstrate its utility as an assessment tool; 3) To show that similar effects are possible with sacral electrical stimulation through a SARS implant device currently used for bladder emptying in SCI. 5 able-bodied volunteers, 11 patients with SCI (6 complete injuries, 5 incomplete injuries) participated in the FMS study. 6 other SCI individuals with a SARS implant were recruited for the SARS study. In order to compare sacral nerve root stimulation against conventional surface FES, 6 complete SCI were included for a surface FES study The results jndicated that sacral nerve root stimulation, either by using FMS or implanted SARS can induce gluteus maximus contractions sufficient to achieve significant changes in ischial pressures and cutaneous hemoglobin and oxygenation during sitting. The magnitude of pressure reduction archived with FMS and SARS were greater than that with conventional surface FES. In addition to these beneficial acute effects, chronic stimulation via a SARS implant may be useful for building gluteal muscle bulk as a further important preventative measure to reduce pressure ulcer in SCI population.EThOS - Electronic Theses Online ServiceGBUnited Kingdo