Relation between median and ulnar nerve function and wrist kinematics during wheelchair propulsion

Objective: To investigate the relation between median and ulnar nerve health and wrist kinematics in wheelchair users. Design: Case series. Setting: Biomechanics laboratory and electrodiagnostic laboratory at a Veterans Health Administration medical center and a university hospital, respectively. Participants: Thirty-five people with spinal cord injury who use manual wheelchairs. Intervention: Subjects propelled their own wheelchair on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanic data were obtained by using force and moment sensing pushrims and a kinematic system. Bilateral median and ulnar nerve conduction studies were also completed. Main Outcome Measures: Wrist flexion, extension, radial and ulnar deviation peaks, and ranges of motion (ROMs) as related to median and ulnar motor and sensory amplitudes. A secondary analysis included peak pushrim forces and moments and stroke frequency. Results: There was a significant, positive correlation between flexion and extension ROM and both ulnar motor amplitude (r=.383, P<.05) and median motor amplitude (r=.361, P<.05). Conclusions: Contrary to our hypothesis, subjects using a greater ROM showed better nerve function than subjects propelling with a smaller ROM. Subjects using a larger ROM used less force and fewer strokes to propel their wheelchairs at a given speed. It is possible that long, smooth strokes may benefit nerve health in manual wheelchair users.