Review Question - QID 217368

The imaging is consistent with a posterior labral tear, which occurs when there are posteriorly directed forces on the arm in a flexed, adducted, and internally rotated position.

Posterior labral tears are a relatively rare source of shoulder pain and instability when compared to anterior labral pathology. They are frequently seen in football linemen, wrestlers, and weightlifters who have repetitive microtrauma to the posterior capsulolabral complex with the shoulder in the compromising flexed, adducted, and internally rotated position. Specific provocative physical exam maneuvers include the posterior load and shift test, Kim test, and Jerk test suggest posterior labral pathology, but formal diagnosis is made on advanced imaging, either MRI or CT arthrogram. Arthroscopic labral repair may be warranted in competitive athletes or those who fail to improve with nonoperative measures.

Antosh et al. thoroughly review the diagnosis and management of posterior shoulder instability. They describe its affinity for athletes participating in high-demand, dynamic posterior loading activities, including weightlifters, football linemen, military, and even in baseball players’ lead shoulders during batting or individuals who participate in rifle shooting. They conclude that in low-demand patients, nonoperative treatment is typically successful and should be considered as the first line of treatment. Active individuals, such as athletes or military members, are candidates for arthroscopic posterior labral repair which has excellent clinical outcomes, high patient satisfaction, and low complication rates.

Bäcker et al. report on the biomechanics of posterior shoulder instability and the complex osseous and soft tissue structures that stabilize the glenohumeral joint. Specifically, they acknowledge that the correct mechanism of injury is not well understood, leading to a lack of consensus regarding treatment regimens and general awareness by physicians. However, they did find that the most important factors that produce posterior shoulder instability are capsular lesions and ruptures of the inferior glenohumeral ligament.

Figure A are axial T1-weighted (left) and T2-weighted (right) cuts of the glenohumeral joint demonstrating signal in-between the posterior labrum (white asterisk) and articular margin (white arrow) consistent with a posterior labral tear.

Incorrect Answers:
Answer 1: Anteriorly directed forces on the arm in a flexed, abducted and externally rotated position can produce anterior instability and a subsequent anteroinferior labral tear.
Answer 2,3,5: These are not compromising positions associated with posterior labral tears.