Discussion:
- 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.