The researchers of “Shoulder External Rotational Properties During Physical Examination Are Associated With Injury That Requires Surgery and Shoulder Joint Loading During Baseball Pitching,” found that shoulder injuries that require surgery were associated with shoulder external rotation flexibility, and that high shoulder external rotation was associated with less risk of injury.
“Throwing arm injuries are common because of the demand on the shoulder. The shoulder is qualitatively checked regularly by team physicians. Excessive instability and joint loading in baseball pitching are risk factors for throwing arm injuries. Knowledge of shoulder flexibility, range of motion, and joint loading may provide new insights for treatments to reduce the likelihood of injury incidence,” Hannah Stokes, BSc and Naiquan (Nigel) Zheng, PhD, wrote.
Stokes is a member of the department of mechanical engineering and engineering at the Center for Biomedical Engineering and Science, University of North Carolina at Charlotte, North Carolina. Zheng is Professor of Mechanical Engineering and Engineering Science Associate and BMR Focus Area Leader, Center for Biomedical Engineering and Science Associate, Gerontology Program at the University of North Carolina. Dr. Zheng also advises the Tampa Bay Rays baseball team.
For their study, they measured pitching kinetics, shoulder rotational tests and self-reported injury questionnaires for 177 collegiate baseball pitchers who required shoulder surgery. The questionnaires were filled out during tests and yearly follow-ups. Follow-up lasted for 5 years.
Overall, shoulder external rotational properties during physical examination were significantly associated with shoulder joint loading in baseball pitching. High shoulder external rotation was associated with 14% to 36% lower shoulder posterior force and adduction, internal rotation and horizontal adduction torque (p < .05).
In addition, high shoulder external rotation before external rotation torque was applied was associated with 13% to 33% lower shoulder inferior force and adduction, internal rotation, and horizontal adduction torque (p < .05). No differences were observed in shoulder joint loading, however.
“High shoulder external rotation may be advantageous because it lowers the force and torque on the shoulder joint,” the researchers wrote.
“The ability to understand shoulder external rotational properties, joint loading, and injury during baseball pitching helps further our understanding of injury mechanisms. The shoulder rotational test shoulder be used as a screening tool to identify players at risk.”
The study was published online in September 23, 2021 in The American Journal of Sports Medicine.
