Imaging in Anterior Glenohumeral Instability1

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. REVIEWS AND COMMENTA Imaging in Anterior Glenohumeral Instability1 r Y n REVIEW Jenny T. Bencardino, MD In the shoulder, the advantages of range of motion are Soterios Gyftopoulos, MD traded for the disadvantages of vulnerability to injury William E. Palmer, MD and the development of instability. Glenohumeral instability 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, Online CME and chronic instability without repeated dislocation. The See www.rsna.org/education/ry_cme.html biomechanics of dislocation and the pathophysiology of labral-ligamentous injury are discussed. The authors dis- Learning Objectives: tinguish the findings that occur in the acutely trauma- After reading the article and taking the test, the reader will tized shoulder from those that typify the chronic unstable be able to: joint. The roles of different imaging modalities are also n Describe the biomechanics of dislocation and the distinguished, including magnetic resonance arthrography pathophysiology of labral-ligamentous injury and the value of specialized imaging positions. The goal n Describe the roles of different imaging modalities in the of imaging depends on the clinical scenario. Image inter- diagnosis of anterior glenohumeral instability n Evaluate the MR imaging findings that can help pretation and reporting may need to emphasize diagnosis radiologists distinguish acute first-time shoulder and the identification of lesions that are associated with dislocation from chronic instability with or without instability or the characterization of lesions for treatment repeated dislocation planning. Accreditation and Designation Statement The RSNA is accredited by the Accreditation Council for q RSNA, 2013 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. 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: [email protected]). q RSNA, 2013 Radiology: Volume 269: Number 2—November 2013 n radiology.rsna.org 323 REVIEW: Imaging in Anterior Glenohumeral Instability Bencardino et al he glenohumeral joint has the Glenohumeral instability can be- Biomechanics greatest range of motion of any come the immediate sequelae of trau- Tmajor articulation in the human matic injury or evolve gradually owing to Dynamic and passive restraints to- body. The trade-off for this mobil- cumulative stresses related to occupa- gether provide glenohumeral stability, ity is vulnerability to injury and the tional or sport-specific activities (2). De- maintaining nearly perfect rotation of development of shoulder instability. pending on the clinical scenario and the the humeral head over the center of Dynamic stabilizers of the joint, in- needs of the treating physician, imaging the glenoid fossa. Dynamic stabilizers cluding the cuff muscles, are insuf- has different roles. In the acute setting include the rotator cuff and long head ficient to maintain normal glenohu- following first-time shoulder dislocation, of biceps as well as pectoralis major, meral location and function (1). Joint MR imaging is used to characterize the latissimus dorsi, and periscapular mus- stability also depends on the passive location and extent of structural dam- cles (1). Passive stabilizers include constraints provided by intact static age and typically demonstrates an obvi- the glenoid rim and concave glenoid structures, especially the glenoid rim, ous, pathognomonic pattern of osseous fossa, labrum, and capsuloligamentous glenoid labrum, and glenohumeral lig- edema, hemarthrosis, and labrocapsu- structures (1). The congruent articu- aments. The vast majority of unstable lar injury. But as dramatic as these MR lar surfaces provide stability through shoulders demonstrate characteristic findings can be, they may not predict the principle of concavity compression, abnormalities of the labral-ligamen- repeated dislocation or the future devel- which is particularly important during tous complex on magnetic resonance opment of glenohumeral instability (3). the midrange of glenohumeral move- (MR) images (2). In the setting of repeated dislocations, ment when the capsular ligaments are when the clinical diagnosis of instabil- lax (4). The surrounding muscles cre- ity becomes unambiguous, MR imag- ate this dynamic joint compression and Essentials ing may be able to show osseous and primary stabilization during the mid- nn Trauma accounts for more than soft-tissue abnormalities that can guide range (5). At the extremes of motion, 90% of first-time anterior shoul- surgical planning and the choice of sta- the glenohumeral ligaments contribute der dislocations. bilization procedure. most to stability, especially the inferior nn Reciprocating humeral and gle- Shoulder instability also occurs in labral-ligamentous complex (5). noid lesions are pathognomonic individuals who deny previous disloca- The glenohumeral ligaments (supe- for articular malalignment (dislo- tions and major traumatic events (2). rior, middle, and inferior) are formed cation) at the time of trauma and In one subset of these patients, func- by discrete capsular bands that attach are strongly associated with in- tional disability and positive provocative to the labrum and adjacent glenoid rim juries to stabilizing soft-tissue testing lead to confident clinical conclu- (5–9). The superior and middle gleno- structures. sions. In another subset, equivocal his- humeral ligaments arise anterosuperi- nn There are two major causes at tory and physical examination lead to orly, just anterior to the biceps tendon. either end of a continuum; at challenges in diagnosis (2). If imaging The superior glenohumeral ligament one end of the spectrum, a is requested, the history may state a merges with the coracohumeral liga- major traumatic event causes question about the presence of rotator ment in the rotator interval and pass- first-time dislocation followed by cuff tear or biceps lesion, possibly mis- es between the supraspinatus and the repeated dislocations requiring leading the radiologist interpreting the subscapularis to the lesser tuberosity lesser degrees of force and imaging study (2). at the bicipital groove. Together with provocation. In this review, we focus on imag- the coracohumeral ligament, the supe- ing findings in three distinct clinical rior glenohumeral ligament functions as nn At the other end of the spec- scenarios. The first scenario involves a primary passive restraint to inferior trum, there is no antecedent acute first-time shoulder dislocation. trauma; glenohumeral hypermo- The second applies to chronic instability, which may be developmen- bility with repeated dislocation. In the Published online 10.1148/radiol.13121926 Content code: tal, leads to multidirectional in- third scenario, there is chronic insta- stability that worsens over bility without repeated dislocation. We Radiology 2013; 269:323–337 months and years. distinguish imaging findings that char- Abbreviations: nn In the latter scenario, instability acterize the acute setting from those ABER = abduction-external rotation causes symptoms due to recur- that characterize the chronic unstable ALPSA = anterior labral-ligamentous periosteal sleeve rent glenohumeral subluxation, joint. We also distinguish the roles of avulsion not dislocation; because the different imaging modalities, including GLAD = glenolabral articular disruption degree of subluxation may be conventional MR imaging versus MR HAGL = humeral avulsion of the glenohumeral ligament IGL = inferior glenohumeral ligament minimal, this condition has also arthrography, and the value of special- 3D = three-dimensional been described clinically as rela- ized imaging positions such as abduc- tive instability. tion-external rotation (ABER). Conflicts of interest are listed at the end of this article. 324 radiology.rsna.org n Radiology: Volume 269: Number 2—November 2013 REVIEW: Imaging in Anterior Glenohumeral Instability Bencardino et al Figure 1 Figure 1: MR images in a 31-year-old male dancer obtained 4 days after acute first-time anterior shoulder

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