- 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 rotator cuff (surface of the infraspinatus and posterior fibers of supraspinatus tendon); 
              -  posterior glenoid impacts the articular surface of the infraspinatus and posterior fibers of the supraspinatus tendon;
              - 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; 
      - exam findings:
              - tenderness over the coracoid has been attributed to a contracture of the pectoralis minor tendon secondary to scapular malposition.
      - MRI findings: posterolateral humeral head edema, posterior labram fraying, partial rotator cuff tear;
      - treatment:
              - capsular stretching and dynamic strengthening of the rotator cuff musculature 
              - arthroscopic findings may reveal an isolated posterior cuff tear (or undersurface fraying) and fraying of the posterior labrum , and increased anterior capsular volume; 
              - w/ posterior impingment and recurrent anterior instability, anterior reconstruction (either open reconstruction or arthroscopic anterior reconstruction) may be indicated; 

  - references:
        - Posterior shoulder pain in throwing athletes with a Bennett lesion: Factors that influence throwing pain, 
        - The posterior impingement sign: diagnosis of rotator cuff and posterior labral tears secondary to internal impingement in overhand athletes. 
        - Posterior superior glenoid impingement: expanded spectrum.   
        - Internal impingement: findings on magnetic resonance imaging and arthroscopic evaluation. 
        - Arthroscopic findings in the overhand throwing athlete: Evidence for posterior internal impingement of the rotator cuff.

Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, January 10, 2013 1:12 pm