Glenohumeral joint dynamics and rotator cuff health in youth manual wheelchair users with pediatric spinal cord injury and dysfunction.

Youth with pediatric-onset spinal cord injury or dysfunction (SCI/D) rely on manual wheelchairs for mobility throughout their lives, leading to prolonged shoulder loading during development and growth. While manual wheelchair use is known to accelerate shoulder degeneration in adults, the biomechanical factors contributing to structural shoulder pathology in youth remain poorly understood. We quantified how glenohumeral joint loading and movement variability during propulsion relates to rotator cuff structure and pathology in 34 youth manual wheelchair users with pediatric-onset SCI/D. Participants underwent motion analysis during wheelchair propulsion at a self-selected speed and shoulder ultrasound. Rotator cuff pathology was identified in 20.6% of participants. Some observed associations suggested that lower intersegmental glenohumeral joint forces and moments coincided with supraspinatus and subscapularis pathology. Similarly, variability in certain glenohumeral joint ranges of motion, forces, and moments was also associated with altered rotator cuff morphology. These findings support a bidirectional relationship between shoulder loading and pathology, suggesting functional and morphological adaptations to repetitive propulsion demands or early tissue compromise. Overall, this work underscores the complexity of shoulder biomechanics in youth manual wheelchair users and highlights the need for longitudinal, multivariate research to distinguish protective adaptations and disuse patterns from early indicators of tendon degeneration.