Biomechanical insights into the aetiology of infraspinatus syndrome.

Objective: Infraspinatus syndrome (IS) results from injury to the suprascapular nerve. For reasons that are poorly understood, volleyball players are at greater risk of developing IS than are athletes who compete in other overhead sports. Differences between the shoulder kinematics of volleyball-related overhead skills and those skills demanded by other overhead sports might explain the pronounced prevalence of IS among volleyball athletes.

Design: Observational, laboratory-based, cross-sectional study.

Setting: The American Sports Medicine Institute.

Participants: Fourteen healthy female Division 1 collegiate volleyball athletes.

Methods: Upper limb biomechanics of 14 healthy female Division 1 collegiate volleyball athletes while spiking and serving were quantified, then compared to the results from data previously obtained from female baseball pitchers and tennis players.

Results: Although the general movement pattern at the shoulder girdle is qualitatively similar for the upper limb skills required by a variety of overhead sports, volleyball spiking and serving result in greater shoulder abduction and horizontal adduction at the moment of ball contact/release than do baseball pitching or tennis serving.

Conclusion: The authors suggest that the unique scapular mechanics which permit the extreme shoulder abduction and horizontal adduction that characterise volleyball spiking and serving place anatomically predisposed volleyball athletes at increased risk for developing cumulative traction-related injury to the suprascapular nerve at the level of the spinoglenoid notch.