Toward understanding mechanisms of inadvertent lower extremity displacements from wheelchair footplates in Veterans with SCI/D: Multi-modal evaluation of leg movements during power wheelchair use.

Veterans with sensorimotor deficits due to spinal cord injuries and disorders (SCI/D) and other neurological disorders often use power wheelchairs (PWC) for independent mobility. While PWC are critically important to improving quality of life, lower limb injuries can occur when the foot is not positioned properly on the footplate

during PWC operation. In Veterans with SCI/D, sensory loss, paralysis, spasticity, contractures and obesity create barriers to recognizing and correcting lower limb mispositioning. Veterans with SCI/D have sustained fractures, abrasions, contusions, pressure injuries, and amputations after inadvertent lower extremity

displacements (ILED) from their PWC foot plates, at an estimated system cost of $970,011 for the first 10 such Veterans admitted to the Cleveland VA SCI/D Center. Veterans Advocates with SCI/D report that ILEDs occur during transfers, pressure relief, colliding with objects, muscle spasms, and driving over rough terrain. PWC

seating functions, like tilt and leg elevation, may misalign the feet on the footplate when returning to upright. Yet, there is little documentation of the root cause of lower extremity injuries in the medical record, and ILED incidence and prevalence are poorly described in the literature. No scientific reports of how the lower limbs

move during WC operation have been identified. This important knowledge can guide interventions to prevent future foot displacements and subsequent injuries. The VA-patented FootSafe system of force and proximity sensors with a wirelessly-connected smart device was developed as an assistive technology to detect foot position relative to the PWC footplates and warn PWC

users when an ILED occurs, thus empowering them to either reposition their legs to safety or call for help if needed. Other AT solutions also may be possible, however. Therefore, to create useful and accurate sensing algorithms in future, it is first critical to understand the potential range of ILEDs and whether different PWC

user groups are more or less vulnerable to these events. As noted above, Persons with SCI/D can serve as an exemplar of PWC users with sensorimotor losses creating risk of ILEDs and subsequent injuries. This research project will use a 3 pronged approach to understanding lower limb movements and ILED

occurrence during PWC mobility. Focus groups of Veterans with SCI/D, their caregivers, and seating specialists will be convened to advise on the ILEDs they are primarily concerned about, how much limb displacement is acceptable and when they feel corrections are required to prevent harm, to design terrains courses and determine PWC speeds needed to

increase likelihood of capturing ILEDs during testing, and to reach consensus on what constitutes a clinically significant ILED and the needed sensitivity for detection by future algorithms. FootSafe will be used in combination with motion capture and depth camera technologies to compare the biomechanics and kinematics of lower limbs motion during PWC operation by Veterans with SCI/D and

neurologically intact PWC users in laboratory and community settings. The FootSafe and 3-dimensional data sets acquired during the lab and community PWC mobility phases will be analyzed using Machine Learning anomaly detection techniques to quantify limb displacements and further understand how the limbs move over time. Video and wireframe diagrams for detected anomalies will be

brought back to the focus groups for their assessment of the clinical relevance as previously noted. Understanding how ILED leading to these injuries occur, in what situations of PWC use and by which PWC users is crucial to solving the problem of ILED-related injuries. Objective ILED documentation will not only

improve development of future assistive technology algorithms to detect and alert PWC users when ILEDs occur, but will also support payor provision of preventative seating system modifications and promote development of regulatory guidelines and unique solutions to prevent these unfortunate injuries.