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Pressure ulcers (PUs) are common and debilitating wounds that arise when immobilized patients do not shift their weight. Blood vessels become occluded and the soft tissues they supply necrose. Current treatment requires prolonged passive tissue load reduction, when individuals are required to be off their seating systems, sometimes in bed for long periods of time. Sometimes surgical repair is required. Even when healed, pressure ulcers have a high recurrence rates and monitary costs range upwards to $50-80K per incident. Most importantly, individuals are restricted in their mobility and their participation in normal daily life. With an aim to prevent these ulcers, neuromuscular electrical stimulation (NMES) will be delivered to key muscle groups via chronically implanted, wireless micro-stimulators to both shift the paralyzed subject’s weight, as well as build up gluteal muscle volume (padding) and musculocutaneous circulation.
The main focus of this project is the investigation of NMES for pressure ulcer prevention in a prospective feasibility trial at Rancho Los Amigos National Rehabilitation Center. Microstimulators will be implanted in spinal cord injured paraplegic and quadriplegic individuals, either during pressure ulcer reconstructive flap surgery that they will already be undergoing, or injected percutaneously in pressure ulcer clinic. These microstimulators will be used to activate gluteal muscles and the hamstrings as hip extensors, to facilitate pressure ulcer healing and prevent recurrences. Outcome measures include tissue health variables (measured by clinical assessment, MRI and muscle perfusion scans), pressure redistribution (measured by an array of pressure sensors), and recurrence rates over a 36 month evaluation period. During this evaluation period, subjects will interact with the clinical and development team to identify real world difficulties with the system and create optimized solutions to assure long term compliance. Once the efficacy of this novel therapy has been proven, we envision its broader application in the general seated/paralysed population: that microstimulators could eventually be inserted percutaneously as they already have been in other clinical applications, being activated and powered via an in-chair antenna.
An early study which used radio-frequency (RF) coupled microstimulators identified several problems with the power of the RF signal and portability of the system. The present proposal will use significantly different microstimulators, which are independently battery powered, requiring considerably less RF power to control. This will allow the development of a more portable system, which will be light weight and minimally intrusive on the subject’s wheelchairs. The new system will require an ON-OFF activation by the subject (at the beginning of the day and any time they leave and re-enter their wheelchair), and a daily recharging of the implanted batteries.
Pre-clinical research necessary to determine appropriate stimulation parameters and protocols for relieving internal tissue pressures during Stimulated Active Seating (SAS), has already been undertaken, allowing preliminary treatment plans to be developed and tested. Additional work to optimize exercise protocols and to fully integrate the SAS program into daily life will be emphasized in the present effort.
In summary, this project intends to provide proof of concept for the clinical application of SAS for Pressure Ulcer Prevention (SASyPUP), including preclinical microstimulator and control software development, and a feasibility clinical trial with an extended period for user assisted development as well as data collection and analysis, Integration of the proposed SASyPUP trial with the Virtual Reality balance exercise program will also be developed in the later stages of the research effort.
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