Throwing Shoulder

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- See: Throwing Injuries:

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- Phases of Throwing:
    - wind up
    - early cocking: deltoid and rotator cuff are active;

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    - late cocking phase:
          - muscle activity:
                  - shoulder is placed in hyper-external rotation;
                  - pectoralis major and the subscapularis (shoulder adductors) and the latissimus and teres major (internal rotators) are placed under eccentric stress;
                         - supraspinatus is also active during this stage (by EMG analysis);
                         - biceps contracts (for elbow flexion)
          - recurrent anterior instability:
                  - posterior glenohumeral pain and anterior subluxation occurs during late cocking and early acceleration phases;
                  - w/ complaints of a painful clicking (dead arm syndrome) during this phase, consider recurrent anterior instability;
                  - references:
                         - Shoulder instability in the overhand orthrowing athlete.  Kvitne RS, Jobe FW, Jobe CM. Clin Sports Med 1995;14:917-935. 
          - posterior impingement:
                  - the hyperextension phase of throwing may be the most important component of internal impingement;  
                  - in the late cocking position (abduction, external rotation, extension) may cause the postero-superior edge of the glenoid labrum to become
                          caught between the humeral head and the rotator cuff;
                  - w/ anterior instability, there will be anterior translation of the humeral head on the glenoid which accentuates impingement
                          of the rotator cuff against the posterosuperior glenoid rim;
                  - arthroscopic findings may reveal an isolated posterior cuff tear (or undersurface fraying) and fraying of the posterior labrum;
                  - w/ posterior impingment and recurrent anterior instability, anterior reconstruction (either open reconstruction or arthroscopic anterior reconstruction)
                          may be indicated;
                  - ref: Posterior shoulder pain in throwing athletes with a Bennett lesion: Factors that influence throwing pain,
           - SLAP lesion - type II
           - quadrilatateral space syndrome
                  - also note that the rare quadrilatateral space syndrome occurs when the arm is abducted and exteranally rotated
                          and is characterized by positional compression of the posterior humeral circumflex artery and the axillary nerve;
          - references:
                  - Rotator cuf and postero-superior glenoid labrum injury associated with increased glenohumeral motion:
                          a new site of impingment syndrome: radiographic evaluation. PA Davidson et al.  J. Shoulder and Elbow Surg. Vol 4. 1995 p 384-390.
                  - Posterior superior glenoid impingement: expanded spectrum.  CM Jobe.  Arthroscopy. Vol 11. 1995. p 530-536.
                  - Impingement of the deep surface of the supraspinatus tendon of the posterosuperior glenoid rim: an arthroscopic study.
                          G Walch et al.  J. Shoulder and Elbow Surg. Vol 1. 1992. p 238-245.
                  - Posterosuperior glenoid impingement of the shoulder: findings at MR imaging and MR arthrography with arthroscopic correlation. 
                          PF Terman et al.  Radiology. Vol 193. p 431. 1994.
                  - A Cadaveric Model of the Throwing Shoulder: A Possible Etiology of Superior Labrum Anterior-to-Posterior Lesions.
                  - Evidence for Posterior Internal Impingement of the Rotator Cuff. KJ. Paley, MD. Arthroscopy:
                          The J. of Arthroscopic and Related Surgery, Vol 16, No 1 (Jan-Feb), 2000: pp 35-40
                  - Impingement of the deep surface of the supraspinatus tendon on the posterosuperior glenoid rim: An arthroscopic study.
                          Walch G, Boileau P, Noel E, Donell ST.  J Shoulder Elbow Surg 1992;1:238-245.
                  - Rotator cuff and posterior-superior glenoid labrum injury associated with increased glenohumeral motion: 
                          a new site of impingement. Davidson PA et al. J. Shoulder Elbow Surg 1995;4:384-390. 
                  - Anterior instability increases superior labral strain in the late cocking phase of throwing.

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    - acceleration phase:
         - pectoralis, latissimus, serratus, and subscapularis are active;
         - rotator cuff and biceps are inactive;
    - follow thru:
         - most activity deliberate;
         - stresses posterior capsule;
         - pain with follow thru (phase 3) may indicate posterior instability;
         - rotator cuff is eccentrically loaded mainly during this phase;;
         - biceps contracts to prevent elbow hyperextension;

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- SLAP lesions:

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- Little League Shoulder: (epiphysiolysis of the proximal humerus);
     - osteochondrosis of the proximal humeral epiphysis due to overuse from throwing;
     - radiographs show physeal widening, fragmentation, and/or sclerosis of the lateral aspect of the proximal humeral physis;
           - lateral metaphyseal fragmentation and/or sclerosis
     - ref: Little Leaguer’s Shoulder. A Report of 23 Cases.

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The diagnosis and treatment of anterior instability in the throwing athlete.

An analysis of 100 symptomatic baseball players.
     DA Barnes, HS Tullos.  Am J. Sports Med. Vol 6. 1978 pp 62-67.

Throwing injuries of the elbow in athletes.
     K De Haven, CM Erarts. Orthop. Clin. North America. Vol 4. 1973. 801-808.

An EMG analysis of the shoulder in pitching. A special report.
     FW Jobe, DR Moynes, JE Tibone, J Perry.  Am J. Sports Med. Vol 12, 1984, p 218-220.

Dynamic electromyographic analysis of the throwing shoulder with glenohumeral instability.
     Glousman R, Jobe F, J Tibone.  JBJS Vol 70-A. 1989. p 220-226.

Electromyographic Analysis and Phase Definition of the Overhead Football Throw.