Shoulder Magnetic Resonance Imaging Abnormalities, Wheelchair Propulsion, and Gender

Abstract

Objective: To investigate the relationship between pushrim forces and the progression of shoulder injuries in manual wheelchair users. Design: Longitudinal case series. Setting: Biomechanics laboratory and magnetic resonance imaging (MRI) facility at a Veterans Health Administration medical center and university hospital, respectively. Participants: Fourteen individuals with spinal cord injury (8 men, 6 women) who used manual wheelchairs. Intervention: Subjects propelled their own wheelchairs on a dynamometer at 0.9 and 1.8m/s. Bilateral biomechanical data were obtained by using force and moment sensing pushrims at time 1. Bilateral shoulder MR images were also completed on 2 occasions, at time 1 and, approximately 2 years later, at time 2. Main Outcome Measures: The peak pushrim forces in a pushrim coordinate system were calculated, weight normalized and averaged over 5 strokes (presented as % body weight). MRI abnormalities were graded by using a summated scale. Differences between scores between times 1 and 2 were calculated. Results: Subjects were divided into 2 groups based on change in MRI score. Seven subjects were in the group with worsening scores (MRI+; mean, 8.14 points; range, 5-16), and 7 were in the group with improving or unchanging scores (MRI-; mean, -1.00 point; range, -5 to 1). There was no significant difference between groups with respect to age, body mass index, or years from injury. There were significantly more women in the MRI+ group (6 women, 1 man) than in the MRI- group (7 men) (P=.001). The MRI+ group used significantly greater weight- normalized radial force, or force directed toward the axle at time 1, to propel their wheelchairs at each speed (P