Review Question - QID 219828

Structure C represents the posterior inferior glenohumeral ligament (IGHL) and posterior capsule, which become pathologically thickened in the setting of internal impingement in the thrower's shoulder (Answer choice C).

Internal impingement occurs in overhead athletes due to repetitive abutment of the undersurface of the rotator cuff and the posterosuperior glenoid. The impingement typically occurs with the arm in maximum abduction and external rotation during the late cocking and early acceleration phases of throwing. The pathoanatomy involves fraying of the articular side of the supraspinatus and infraspinatus, posterior and superior labral lesions, thickening of the IGHL and posterior capsule which form the characteristic "Bennett lesion" when calcified, cystic changes within the greater tuberosity of the humerus, and cartilage damage at the level of the posterior glenoid. First-line treatment typically includes cessation from throwing and physical therapy with a focus on posterior capsular stretching, rotator cuff strength balancing, scapular stabilization, and kinetic chain coordination.

Gelber et al. review the thrower's shoulder. The authors note that overhead athletes subject their shoulders to extreme repetitive torque, compression, distraction, and translation stresses, resulting in adaptive changes of the soft tissues and osseous structures within and around the glenohumeral joint. Specifically, injuries to the shoulder of the overhead athlete can be generally classified into three groups: internal impingement, internal impingement with acquired secondary anterior instability, and primary anterior or multidirectional instability. They conclude that although advances in surgical techniques have allowed surgeons to address the pathology in these groups, merely attempting to restore the shoulder to so-called normal can adversely alter adaptive changes that allow high levels of performance.

Corpus et al. reviewed the evaluation and treatment of internal impingement of the shoulder in overhead athletes. The authors note that “internal impingement” is a term used to describe a constellation of symptoms that result from the greater tuberosity of the humerus and the articular surface of the rotator cuff abutting the posterosuperior glenoid when the shoulder is in an abducted and externally rotated position. They concluded that outcomes of operative treatment have been mixed, therefore intense non-operative treatment should remain the focus of treatment.

Figure A depicts the phases of throwing with the late cocking phase highlighted. Figures B and C demonstrate coronal and axial proton-density, fat-saturated MRI slices showing a combination of findings suggestive of internal shoulder impingement consisting of cysts within the humeral head underlying the superior fibers of infraspinatus, undersurface fraying of the superior fibers of infraspinatus, tendinosis and intrasubstance delamination involving the posterior fibers of supraspinatus, significant fraying of the posterosuperior glenoid labrum, and thickening of the inferior glenohumeral ligament. Figure D represents labeled coronal and axial MRI images of the same shoulder with "A" depicting the tendons of the posterosuperior rotator cuff, "B" the acromion, "C" the posterior IGHL, "D" the biceps tendon, and "E" the anterior glenoid labrum.

Incorrect Answers:
Answer 1: Structure A represents the posterosuperior rotator cuff tendons which become thinned, not thickened, in the setting of internal impingement.
Answer 2: Structure B represents the acromion that may be spurred in cases of subacromial impingement and may be associated with bursal-sided rotator cuff tears, but is not the cause of pathology in the setting of internal impingement.
Answer 4: Structure D represents the biceps tendon, the thickening of which is not associated with the causative pathology in internal impingement.
Answer 5: Structure E represents the anterior glenoid labrum which can actually become thinned rather than thickened in the setting of obligate translation due to posterior capsular thickening, which may cause micro-instability directed anteriorly.