"Shoulder Impingement in the throwing athlete"-Issue 7

     Throwing a baseball is one of the fastest and most violent maneuvers to which the shoulder joint can be exposed.  Each pitch requires generating high levels of force through the trunk and legs in order to accelerate the ball, followed by extreme control from the shoulder to slow this force as the ball is released.
     Repetitive throwing at this high speed increases the stress and strain on the arm of the young athlete, often resulting in injury.  These injuries typically affect the rotator cuff muscles, labrum, and/or joint capsule.  The athlete will initially report decreased pitching speed and control, require a longer warm up period, and experience shoulder pain during the latter part of their throwing motion. 
     Impingement syndrome involves a mechanical compression of the rotator cuff tendons and/or bursa underneath the acromion. As the athlete raises his/her arm overhead to throw, the muscles crossing the shoulder joint are pinched inside of the joint resulting in sharp pain and irritation along the shoulder.  See the diagram above for a better visual understanding of where this occurs.
     Impingement sydrome can occur for a variety of reasons.  A thorough evaluation by a medical physician or physical therapist to determine the source behind the pain is key. The two most common causes are poor mechanics and overuse.  The risk of injury increases tremendously when these two factors are combined.
     When a pitcher has poor mechanics, the shoulder joint is not as effective at slowing the high levels of force generated through the legs.  This creates undue stress for the muscles and capsular structures of the shoulder joint.  A common break down in throwing mechanics is a lack of follow through.
     To achieve the speed required to pitch effectively, seasoned throwers will develop an excess amount of shoulder external rotation.  The greater the arm is able to externally rotate, the more time it has to pick up speed before the ball releases.  Without adequate follow through, the arm is forced to decelerate too quickly, placing extreme stress across the shoulder joint. 
     When this is combined with repetitive throwing without sufficient rest periods, the problem amplifies.  Mild cases of impingement syndrome could quickly progress into a more serious issue if the young athlete ignores early signs of pain and continues to overuse the arm.
     Throwing injuries to the shoulder can be extremely complex.  Prevention is key in avoiding injury.  Studies show that in pitchers ages 9-14: curveball pitches were associated with a 52% increased risk of shoulder injury, sliding pitches were associated with an 86% increased risk of elbow pain, and change up pitches were associated with a 29% increased risk of shoulder pain.  Studies also show that in pitchers ages 14-20: there is a 5x greater risk of shoulder surgery for players who participate in sport >8 months/year; and that risk of injury increases with pitching speeds >84mph, >80pitches/game, and participation in showcases.
     Parents and players should become familiar with the pitching guidelines established by Little League Baseball (http://www.littleleague.org/).  To learn more about this specific throwing injury and others, contact your local physician or physical therapist.


References:
1. Scolaro et al. The Thrower's Shoulder. University of Pennsylvania Orthopedic Journal. 2011 May; 20:53-57.
2. Mahaffey et al.  Shoulder Instability in Young Athletes. Am Fam Physician. 1999 May; 59(10):2773-2782.
3. Seroyer et al. Shoulder Pain in the Overhead Throwing Athlete. American Orthopedic Society for Sports Medicine. 2009; 108-120.
4. Lyman et al. Effect of pitch type, pitch count and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. The American Journal of Sports Medicine. 30(4):463-468,2002.
5. Andrews et al. Kinematic and kinetic comparision of baseball pitching among various levels of development. Journal of Biomechanics. 32(12):1371-1375, 1999.