An overhead thrower must have tremendous shoulder range of motion to generate acceleration, yet have enough stability in the bony and soft tissues to prevent injury from the high forces associate with pitching. Any disruption in this balance can lead to excess strain on one or more structures in the kinetic chain.
How does this affect younger athletes?
We know that overhead sports torque the humerus. The glenohumeral joint is designed for mobility; and anchored to a relatively stable scapula and torso. In youth baseball pitchers, excessive humeral torque can stress the vulnerable proximal epiphyseal cartilaginous growth plate, leading to a painful condition called Little League Shoulder.
Function can change structure.
As you can see in the following radiographs, repetitive stress without adequate recovery can lead to permanent shoulder deformation- specifically, posterior orientation of the humeral head (proximal humeral retro-torsion), or separation of the epiphysis from the diaphysis (epiphysiolysis).
These imaging modalities confirm that excess activity is truly changing the structure of the shoulder.
Just for fun, lets do the numbers
When throwing a pitch, internal rotation of the humerus has been measured as high as 7000 degrees/ per second. Distraction forces across the shoulder have been calculated as high as 108% of body weight. That's right; imagine having an eleven year old strapped to your arm while throwing a baseball. To counteract distraction forces, the deltoid and rotator cuff muscles produce nearly 1090 N of compressive force, 400 N of posterior shear, and 97 N-m of horizontal abduction torque during the deceleration phase.
More trouble on the horizon
These high forces place stress on the rotator cuff and the supporting structures of the shoulder, especially the superior labrum. (Check out this prior SLAP blog or watch this video of 3 useful tests for SLAP lesions.) Retroversion of the humeral head also shifts the glenohumeral center of rotation posteriorly, producing excess external rotation and decreased internal rotation. These young pitchers are essentially creating unilateral upper crossed syndrome that consequently opens them up to a host of impingement related problems. (To learn more, review this 15 minutes to Clinical Excellence video describing Upper Crossed Syndrome.)
Chiropractic evidence based management
Overuse is the underlying culprit for Little League Shoulder as well as most other growth plate injuries. One of our most important jobs is to educate young pitchers and their parents about the importance of limiting pitches- including practice pitches. The MLB PitchSmart site provides useful guidelines as well as current youth pitch count limits.
Unfortunately, not all players and coaches follow these guidelines and even when they do, injuries still occur. Pain is not normal and should not be overlooked, especially in adolescents. Clinicians should approach bony injuries like little league shoulder, similar to how they would manage lumbar spondylolysis or other stress fractures. Rest, Re-Image, then Retrain.
First, educate the athlete on the importance of Rest for this injury and regularly throughout season. Then Re-image to assess for complete healing after 4-8 weeks. Finally, Retrain the movements and/or imbalances that caused this condition in the first place. The more chiropractic clinicians and their patients understand HOW something happens, the greater the effectiveness of our management.
1. Nickolas G. Garbis, Edward G. McFarland Understanding and Evaluating Shoulder Pain in the Throwing Athlete Phys Med Rehabil Clin N Am 25 (2014) 735-761
2. Serover ST et al. The Kinetic Chain in Overhand Pitching Its Potential Role for Performance Enhancement and Injury Prevention Sports Health. 2010 Mar; 2(2): 135-146.