BIOMARKERS OF UPPER-EXTREMITY SOFT TISSUE PATHOLOGY IN WHEELCHAIR USERS WITH SPINAL CORD INJURY

Wheelchair users with spinal cord injury (SCI) use upper-extremities to perform most activities, which may lead to upper-extremity pain. Wheelchair transfers and propulsion expose shoulder and wrist soft tissues to repetitive and forceful loads that can contribute to pathology. The proceeding investigations aim to further understand how wheelchair activities contribute to the development of soft tissue pathology using ultrasound and chemical biomarkers. The first three studies describe how wheelchair transfers effect ultrasound markers for pathology. A sample of wheelchair users with SCI was recruited and performed eighteen transfers within 10 minutes. Ultrasound images of the biceps and supraspinatus tendons were collected before and after transfers to assess tendon width, brightness, and composition. Clinical ultrasound markers were collected at the start of the protocol. Better transfer technique correlated with fewer ultrasound markers of shoulder pathology, and less transfer-related shoulder pain. Repeated-transfers acutely increased biceps tendon width and median nerve cross-sectional area; changes were influenced by greater bodyweight and specific transfer skills. A novel method of measuring glenohumeral joint (GHJ) inflammatory cytokines, using microdialysis, was developed for the final study. Six able-bodied veterans and one individual with SCI were recruited. A microdialysis catheter was inserted into the posterior GHJ space under ultrasound guidance. Participants performed a wheelchair propulsion and transfer protocol. Microdialysis samples and ultrasound were collected before and after the activity, and 30 and 60 minutes post-activity. IL-1RA and RANTES changed after the activity. Smaller RANTES increases were correlated with greater propulsive forces. Greater changes in IL-8 and IL-1RA were associated with darker tendons after activity, which indicates intratendinous edema. The findings suggest that inflammatory cytokine expression (local to the GHJ) contributes to rotator cuff tendinopathy. Furthermore, forceful upper-extremity activity may contribute to tendinopathy by amplifying cytokine expression. Biochemical markers are a valuable measure of inflammation that is reflective of soft tissue pathology and may provide investigators with a sensitive method to determine different wheelchair techniques that dampen the inflammatory response. Results from these studies indicate that wheelchair activities may cause an acute inflammatory response that affects tendon health, and that using better technique may help prevent the development of pathology