Shoulder Instability in Children: Muscle Activity and Movement

The aim of this study is to identify factors responsible for recurrent shoulder instability in children. Shoulder instability, i.e. complete or partial dislocation of the shoulder joint, is common in children, resulting in pain and disability. Recurrent instability can damage the shoulder joint resulting in the premature development of arthritis. Rehabilitation approaches are preferred over surgical methods for the growing child e.g. physiotherapy to restore movement and prevent further instability. Existing rehabilitation procedures are based on addressing factors assumed to be responsible for instability e.g. physiotherapists may try to increase shoulder stability by building up the shoulder muscles to compensate for the damaged ligaments. It is evident however that the mechanisms of shoulder instability are not well understood, as failure rates for physiotherapy are high, with 70% - 90% of children continuing to suffer recurrent instability. This is an observational, cross-sectional study of children (aged 8 to 18) presenting with shoulder instability of any origin, traumatic or atraumatic (n=15) and an age-matched sample (n=15) with no history of shoulder problems. Muscle activity and movement pattern differences will be measured using non-invasive 3D motion capture and surface electromyography, to identify factors responsible for instability. Only a single visit to the site will be required (The Orthotic Research \& Locomotor Assessment Unit (ORLAU) based at The Robert Jones \& Agnes Hunt Orthopaedic Hospital NHS Foundation Trust in Oswestry.). If investigators better understand the mechanisms associated with instability, physiotherapy interventions to reduce dislocations and disability can be better targeted. If specific patterns of activity associated with instability are identified, these could be addressed through personalised and improved exercise prescription and rehabilitation. Additionally, causes of instability for which physiotherapy may not be appr