Internal Impingement of the Shoulder Internal Impingement of the Shoulder

Objective: To review internal impingement of the shoulder. Design: Review article. Anatomic & Biomechanical Factors: Internal impingement is typically understood to be the impingement of the cuff on the posterior-superior labrum, with shoulder abduction and external rotation, a position seen in overhead athletes. While pinching of the cuff on the posterior labrum can be seen in normal subjects, repetitive and forceful maneuvers of overhead athletes can lead to a cascade of pathologic findings. Internal impingement of the shoulder, fraying of the posterior cuff and/or posterior-superior labral fraying, and tearing are rarely isolated conditions. Associated factors and perhaps causative factors include anterior glenohumeral instability, superior labrum anterior and posterior lesions, posterior glenohumeral internal rotation deficit (GIRD), and "sick scapular syndrome." Presentation: Patients present typically with posterior glenohumeral joint line pain with shoulder abduction and external rotation, the position of late locking with pitching. A detailed history and physical exam will likely produce associated conditions of GIRD, anterior instability, and scapular dyskinesis. Symptoms that localize to the posterior joint line in abduction and external rotation are termed "internal impingement signs." If this posterior pain is relieved with a relocation maneuver, it is very suggestive of internal impingement. Imaging: Plain imaging may reveal exostosis of the posteriorinferior glenoid rim, sclerosis at the greater tuberosity, rounding of the posterior glenoid rim, and osteochondral lesions of the posterior humeral head. MRI is essential in evaluating for internal impingement. MRI typically reveals undersurface cuff tears and posterior and/or superior labral tears. Contrast material is typically used. The authors caution that many of these imaging findings can be found in asymptomatic throwers and should be understood in the context of the history and physical exam. Treatment: Many throwers can be treated nonoperatively. After a period of rest and medications, a comprehensive rehabilitation program is initiated to stretch the tight posterior structures associated with GIRD, and to strengthen rotator cuff muscles and scapular stabilizers to improve scapular mechanics. If nonoperative treatment fails, surgical management should be considered. While essential lesions appear to be the posterior-superior labral tearing or fraying and cuff fraying, the literature suggests to correct all other associated pathology, in particular anterior instability. Conclusions: Shoulder internal impingement in the overhead athlete is a complex multifactorial condition that is associated with GIRD, scapular dyskinesis, and anterior shoulder laxity. Reviewer's Comments: This well-written article deals with a complex and poorly understood condition. Using an extensive bibliography, the authors present a comprehensive evolution of the understanding of internal impingement. They provide an algorithm that simplifies the approach and management of internal impingement. More images would have helped in understanding some of the complex concepts presented. I strongly encourage all physicians taking care of overhead athletes to read this article. (Reviewer-John H. Wilckens, MD).