REVIEWS AND COMMENTARY n REVIEW Radiology: Volume 269: Number 2—November 2013 n radiology.rsna.org 323 Imaging in Anterior Glenohumeral Instability 1 Jenny T. Bencardino, MD Soterios Gyftopoulos, MD William E. Palmer, MD In the shoulder, the advantages of range of motion are traded for the disadvantages of vulnerability to injury and the development of instability. Glenohumeral insta- bility encompasses a broad spectrum of clinical com- plaints and presentations. The diagnosis can be obvious or entirely unsuspected. Imaging findings depend on nu- merous factors and range from gross osseous defects to equivocal labral abnormalities and undetectable capsular lesions. This review focuses on the imaging findings in three distinct clinical scenarios: acute first-time shoulder dislocation, chronic instability with repeated dislocation, and chronic instability without repeated dislocation. The biomechanics of dislocation and the pathophysiology of labral-ligamentous injury are discussed. The authors dis- tinguish the findings that occur in the acutely trauma- tized shoulder from those that typify the chronic unstable joint. The roles of different imaging modalities are also distinguished, including magnetic resonance arthrography and the value of specialized imaging positions. The goal of imaging depends on the clinical scenario. Image inter- pretation and reporting may need to emphasize diagnosis and the identification of lesions that are associated with instability or the characterization of lesions for treatment planning. q RSNA, 2013 1 From the Department of Radiology, NYU Hospital for Joint Diseases, NYU Langone Medical Center, NYU Center for Musculoskeletal Care, NYU School of Medicine, 301 E 17th St, Sixth Floor, New York, NY 10003 (J.T.B., S.G.); and Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Mass (W.E.P.). Received October 4, 2012; revision requested November 5; revision received January 27, 2013; accepted February 14; final version accepted February 26. Address correspondence to J.T.B. (e-mail: Jenny.Bencardino@nyumc.org). q RSNA, 2013 Learning Objectives: After reading the article and taking the test, the reader will be able to: n Describe the biomechanics of dislocation and the pathophysiology of labral-ligamentous injury n Describe the roles of different imaging modalities in the diagnosis of anterior glenohumeral instability n Evaluate the MR imaging findings that can help radiologists distinguish acute first-time shoulder dislocation from chronic instability with or without repeated dislocation Accreditation and Designation Statement The RSNA is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. The RSNA designates this journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit TM . Physicans should claim only the credit commensurate with the extent of their participation in the activity. Disclosure Statement The ACCME requires that the RSNA, as an accredited provider of CME, obtain signed disclosure statements from the authors, editors, and reviewers for this activity. For this journal-based CME activity, author disclosures are listed at the end of this article. Online CME See www.rsna.org/education/ry_cme.html Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.