Objective: Shoulder instability is a common cause of morbidity among professional rugby union players. This study explores whether the risk of shoulder dislocation is associated with innate shoulder laxity.
Design: Retrospective cohort study.
Setting: Clinical sports medicine research at professional rugby clubs.
Participants: One hundred sixty-nine healthy rugby players (mean age 25.1 years) with no history of instability in either shoulder and 46 players (mean age 27.5 years) with shoulder instability in one shoulder (patient group).
Main outcome measures: Anterior, inferior, and posterior laxity was measured in both shoulders for healthy players and in the uninjured shoulder only for injured players using dynamic ultrasound.
Results: There was no significant difference between the nondominant (anterior: mean 2.9 ± 1.2 mm; inferior: mean 3.1 ± 1.0 mm; posterior: mean 5.1 ± 1.7 mm) and dominant (anterior: mean 3.1 ± 1.1 mm; inferior: mean 2.9 ± 1.0 mm; posterior: mean 4.9 ± 1.7 mm) shoulders in healthy players (P > 0.05). The comparison between healthy shoulders (anterior: mean 3.0 ± 1.2 mm; inferior: mean 3.0 ± 1.0 mm; posterior: mean 5.0 ± 1.7 mm) and the uninjured shoulder (anterior: mean 4.2 ± 1.7 mm; inferior: mean 3.4 ± 1.2 mm; posterior: mean 6.2 ± 3.0 mm) from injured players identified that players with unstable shoulders have a significantly higher shoulder translation in their uninjured shoulder than healthy players (P < 0.05).
Conclusions: Formal assessment of shoulder translation using dynamic ultrasound should enable sports medicine practitioners to identify players at greatest risk of subsequent shoulder instability for targeted prehabilitation programs.