Internal and External Rotators Muscle Strength Ratio and Acromio-Humeral Distance as Predictors of Shoulder Injuries in Volleyball Players

Abstract

Abstract Purpose We aimed to investigate the ratio between strength of internal and external rotators of shoulder using handheld dynamometer and acromio-humeral distance actively and passively using musculoskeletal ultrasound to identify a relation between strength imbalance and shoulder joint injuries in Egyptian volleyball players. Methods A case control study, carried out on 60 volleyball players, subdivided into 2 subgroups, 30 with shoulder pain (injured group) and 30 apparently healthy players as a control group. The internal and external rotator muscles were measured with and held dynamometer, and acromio- humeral distance was measured using musculoskeletal ultrasound. Results injured group included 10 female players (33.3%) and 20 male players (66.7%), age ranged between 16-30 years old, while control group included 4 females (13.3%) and 26 males (86.7%). Internal and external rotation strength ratio was less than 0.9 in injured group in the dominant arm, in favor of the normal group with statistical difference between them (p < 0.004). Acromio-humeral distance actively in injured group ranged from 0.45 to 0.87cm with mean ±SD of (0.64±0.07), less than normal group which ranged from 0.7 to 1cm with a mean ±SD of (0.79±0.08) (p < 0.000) Conclusion Weakness of external rotators muscles strength will decrease ratio between external rotator/internal rotator muscles, reducing the acromio-humeral distance especially during abduction, leading to shoulder injuries among volleyball players.