Improving Shoulder Health for Persons with SCI through an Ergonomic Wheelchair
People with Spinal Cord Injury (SCI) utilize manual wheelchairs (MWCs) for independent mobility, relying heavily on their upper limbs for propulsion as well as weight support for moving in and out of the chair. This repetitive use of upper limbs can lead to shoulder pain and injury that reduces user independence and quality of life. A recent study identified a new push-rim position for MWCs that reduces muscle demand and potentially risk of injury. The purpose of this study was to prepare pilot data to compare subacromial supraspinatus tendon compression risk against the coracoacromial arch in persons with SCI and shoulder pain using a traditional MWC push-rim position and those using a MWC with the theoretically optimal push-rim placement. Supraspinatus tendon compression risk was measured by analyzing propulsion trials of subject-specific rigid body models created using magnetic resonance (MR), computerized tomography (CT), and biplane radiographic imaging. The theoretical push-rim position was not found to have significant effects on shoulder joint kinematics or minimum distance from the supraspinatus tendon insertion to the coracoacromial arch. The supraspinatus tendon was found to be at risk for compression during the end of the push phase of propulsion. The phase of highest risk for propulsion was found to correspond with peak flexion and abduction values. These findings provide pilot data for assessing the risk of supraspinatus tendon compression in the theoretical MWC push-rim position in comparison to the standard push-rim position.