535 - Square Pegs, Round Holes: A Review of Evaluation, Diagnosis, and Treatment of a Case of Quadrilateral Space Syndrome

Case Diagnosis: Quadrilateral Space Syndrome in a 45 year-old female veteran

Case Description: A 45-year-old female presents for evaluation of left shoulder pain. She underwent rotator cuff repair 9 months prior, but suffered residual posterior shoulder pain worse with overhead activities, and weakness in abduction and external rotation. She localized the pain to two primary sites: medial and lateral to the glenohumeral joint line (GHJ). Exam findings were notable for tenderness in the quadrilateral space, weakness in abduction, and limited range of motion in abduction secondary to pain. Ultrasound findings mirrored a recent MRI with rotator cuff tendon pathology, however special testing did not suggest the rotator cuff as a primary pain generator. On ultrasound of the primary point of tenderness, the quadrilateral space and axillary nerve were visualized. The decision to perform a diagnostic ultrasound guided axillary nerve block was made, as well as nine total trigger point injections (TPI’s) medial to the GHJ line for suspected myofascial pain.

Discussions: The patient had 90% improvement in pain localized to the quadrilateral space, and range of motion increased to 180 degrees in previously limited motions at the shoulder. The diagnosis of quadrilateral space syndrome (QSS) was based the history, physical exam, and immediate improvement in pain following diagnostic axillary nerve block. The patient was given physical and massage therapy, as well as activity modification.

Conclusions: Quadrilateral space syndrome is often a diagnostic challenge as it is frequently overshadowed by more common shoulder pathologies, and the reliability of common diagnostic studies are still being explored. In this patient, axillary nerve block provided swift diagnostic confirmation and allowed prompt treatment.