Factors associated with thoracic spinal cord injury, lesion level and rotator cuff disorders

Background: The study was concerned with the secondary functional compromise persons with long-term paraplegia contend with, that has been shown to be associated with wheelchair use. Of particular interest was the relationship between the level of thoracic spinal cord injury (SCI) and factors predisposing to rotator cuff disorders (RCD), one of the most common upper extremity musculoskeletal complications linked with long-term SCI. Disorders of these peri-articular structures have previously been associated with impaired trunk postural control and abnormal muscle strength ratios in both able-bodied groups and in paraplegic athletes. Despite their neurologically intact shoulder joint musculature, high-level and low-level paraplegics have different degrees of trunk and pelvic stability available to them during activities of daily living (ADL). This fundamental functional anatomical difference between high-level and low-level paraplegics had not previously been related to the diagnosis of RCD in a non-athletic long-term paraplegic population. Methods: A descriptive cross sectional study was undertaken to demonstrate the differences in the prevalence of clinically diagnosed RCD in a high-level (n = 22) and a low-level (n = 20) group of persons with long-term paraplegia. Any perceived differences were then related to the functional anatomical variations between the two groups. Inferences were made based on factors predisposing to RCD known to exist among both able-bodied and paraplegic athletes. The 42 subjects completed the Wheelchair User's Shoulder Pain Index (WUSPI) to establish the presence or absence of shoulder pain and the Musculoskeletal Function Assessment (MFA) instrument to determine differences in functional ability and perceived degree of difficulty within five categories of ADL. Each participant underwent a clinical examination using validated provocative clinical tests and isometric muscle strength ratio testing. Results: There was a higher prevalence of RCD in the high-level group (P=0.009) which correlated with decreased trunk control (P = 0.009). Differences in ability to perform functional tasks were not shown to be greater in the high-level group, although there was a higher degree of perceived difficulty in ADL. Muscle strength imbalances between the shoulder adductors and abductors were shown to be greater in the high-level group. Conclusions: The results of this study suggest that the functional anatomical differences that exist within paraplegia contribute to the propensity of high-level paraplegic persons to suffer from RCD. These findings send a clear message to service-providers that greater acknowledgement of the differences in trunk postural control specific to the level of thoracic SCI is required. This may have implications for the prescription of wheelchairs, assistive devices and instruction for alternative ADL techniques to this specific population.