Little League Shoulder
Little League Shoulder is a common throwing injury among young baseball pitchers. The medical term for this problem is humeral epiphysiolysis. In this study researchers try to find out the forces around the shoulder that lead to this condition.
They filmed 14 youth baseball pitchers throwing fastballs and analyzed the motion. The pitchers were all right-handed 12 year-old boys who could throw a 50 mph fastball. Front and side views were taken during 10 fastballs pitched by each one with maximum effort.
The force and torque on the shoulder joint were calculated. The researchers looked for a link between pitching biomechanics and shoulder injury. They think these forces can twist the humerus (upper arm bone). The torque may deform the still-growing bone in the shoulder joint. The result is humeral epicondylitis.
There are other factors to think about when looking at the cause and effect of Little League Shoulder. The videos showed joint distraction during forward motion of the pitch. This force was much less than the rotation or twisting of the arm-cocking phase of the pitch. There's also number of years of pitching and frequency or duration of each pitching session to think about.
The authors suggest more study is needed on pitching biomechanics in young adolescent pitchers. It's important to find out which factors are the most likely ones to cause lesions. Training and practice can be changed to prevent injuries.
Michelle B. Sabick, PhD, et al. Biomechanics of the Shoulder in Youth Baseball Pitchers. In The American Journal of Sports Medicine. November 2005. Vol. 33. No. 11. Pp. 1716-1722.