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Which of the following is true of the scapula during an overhead throwing motion?
It maximally retracts on ball release
It protracts during late cocking to prevent impingment on the rotator cuff
It must rotate in the cocking and acceleration phases to prevent impingement on the rotator cuff
It must remain fixed during the throwing motion to impart maximal energy
It has no effect on concavity-compression
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The scapula has an integral role in the overhead throwing motion. It must rotate during cocking and acceleration to clear the acromion to prevent impingement on the rotator cuff. The phases of throwing are seen in Illustration A.
Kibler describes 5 important roles of the scapula during throwing: 1. provide a stable glenohumeral articulation; 2. retraction and protraction; 3. elevation of the acromion; 4. serve as a base for muscular attachment; 5. to be a link in the kinetic chain.
Burkart et al. created the acronym "SICK" scapula (Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement) to describe common signs and symptoms in the disabled throwing shoulder. This is felt to be an overuse muscular fatigue syndrome and is a recognized cause of shoulder pain in the throwing athlete.
1. & 2. The scapula maximally retracts during late cocking and protracts during acceleration and ball release (through activity of the serratus anterior muscle, which is innervated by the long thoracic nerve).
4. The scapula is dynamic and normal motion is needed to generate maximal force transfer.
5. The scapula keeps the humeral head centered thereby increasing concavity-compression and therefore stability.
Am J Sports Med. 1998 Mar-Apr;26(2):325-37. PMID: 9548131 (Link to Abstract)
Kibler, AJSM 1998
Burkhart SS, Morgan CD, Kibler WB.
Arthroscopy. 2003 Jul-Aug;19(6):641-61. PMID: 12861203 (Link to Abstract)
Burkhart, ASCOPY 2003
Title: Anatomy and Biomechanics of the Elbow Speaker: Nikhil N Verma, MD Length:...
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