Rare Subscapularis Anterior Leading Edge Tear following Traumatic Posterior Shoulder Dislocation: A Case Report

Introduction: A patient presented with traumatic posterior shoulder dislocation and underwent a diagnostic arthroscopy, where an acute subscapularis anterior leading edge tear was identified. This tear patient is exceptionally uncommon, having only been cited in the literature 5 times as of 2013, and to our knowledge, has no known documented cases since. This report seeks to summarize challenges associated with such a rare diagnosis by presenting a case where this rare presentation was timely diagnosed and treated with an optimal outcome, and to highlight pertinent details of the case that are critical to not miss this diagnosis in the future. Case Report: This patient is a 45-year-old male who suffered a motor vehicle-pedestrian collision and was diagnosed with left posterior shoulder dislocation resulting in shoulder instability. Physical exam demonstrated signs of both shoulder instability as well as cervical radiculopathy. No other workup or history-taking yielded significant results, other than a distant past medical history of acute neurological distress from traumatic brain injury. The treatment plan consisted of diagnostic arthroscopy with the expectation of finding associated soft tissue and labral pathology and possible Bankart and other indicated soft tissue repair for instability. Upon arthroscopic investigation, not only was a posterior labral tear identified, but also an unexpected anterior edge subscapularis tear. The patient demonstrated rapid pain relief in the immediate post-operative period. Conclusion: Acute posterior shoulder dislocations of the shoulder are seldomly reported in the literature, with even fewer cases reporting on associated rotator cuff tears with this injury. Due to the challenges associated with diagnosing subscapularis tears following posterior shoulder dislocation, we encourage standardization of the variable terminology of subscapularis tear classifications and for surgeons to be aware of the potential of subscapularis pathology with frontal impact injuries. With the increase of motor vehicle accidents, we postulate that this rare scapularis tear patten may become more prevalent and requiring an expanding body of literature on the topic. Keywords: Posterior shoulder dislocation, posterior shoulder instability, subscapularis, anterior leading edge tear, shoulder arthroscopy, and rotator cuff tear.