Acute Rotator Cuff Tendon Changes Associated with Wheelchair Propulsion

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DESCRIPTION (provided by applicant): Due to lower limb paralysis, individuals with spinal cord injury (SCI) rely extensively on their upper limbs for mobility and activities of daily living (ADL). Thus, any loss of upper limb function significantly affects mobility and independence. Unfortunately upper limb pain is very common in manual wheelchair users, with shoulder pain present in between 30% and 73% of manual wheelchair users (MWUs). The vast majority of investigators studying shoulder pain in MWUs have proposed that wheelchair propulsion is, in part, the cause of shoulder pain and pathology. The most common diagnoses related to musculoskeletal shoulder pain in chronic SCI are impingement syndrome and rotator cuff disease. While chronic upper extremity changes have been well documented, no research has investigated acute changes to the rotator cuff that occur as a result of wheelchair propulsion. Ultrasound is a non-invasive, convenient method that has been used to examine soft tissue structures of the shoulder. Symptoms of pathology of the rotator cuff detected by ultrasound include hypoechoic (due to increased fluid) tendon appearance, hypertrophy of the long biceps tendon, and an increased biceps-supraspinatus/infraspinatus tendon diameter ratio. The purpose of this study is to measure acute changes in the soft tissue of the shoulder occurring as a result of a wheelchair propulsion task. We will collect baseline images of biceps, supraspinatus and subdeltoid bursa. Subjects will then propel their wheelchair for ten minutes while kinetic and kinematic data are collected. Post-propulsion ultrasound images will be collected using special techniques to maximize repeatability and consistency of the ultrasound readings. A marker will be place on the skin that is visible on the ultrasound image during the baseline ultrasound exam. Baseline and post-propulsion ultrasound exams will use this marker as a reference point in order to ensure the same ultrasound probe position, tilt, and orientation for both imaging sessions. We will measure changes in the infraspinatus, supraspinatus and biceps tendons and related these changes to biomechanical measures, and baseline soft tissue characteristics. We believe that the acute changes in tendons are part of the pathologic process that leads to chronic changes and pain. At the completion of this grant we will have determined how acute changes in soft tissue as a result of wheelchair propulsion relate to specific biomechanics as well as to chronic soft tissue pathology. Understanding these relationships will provide insight into the biomechanics of repetitive strain injury at the shoulder and will provide an opportunity to test interventions. Specifically, if we can show that a propulsion training program or change in wheelchair setup or design leads to a decrease in acute changes in soft tissue, we will know that our interventions make a difference. In the final phase of this grant we will collect pilot data that will demonstrate our ability to reduce acute changes in the soft tissue of the shoulder. This type of information is critical to appropriate selection of interventions in subsequent controlled trials.