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natomy, Examination, and Imaging of the Shoulderuong Nguyen, MD, FRCSC

A thorough understanding of the dynamic and static stabilizers of the shoulder, a carefuland complete history and physical examination of the patient, and the ordering of theappropriate imaging tests will help the surgeon decide on the optimal management for thepatient with instability. The particular treatment chosen will depend on the accurateclassification of the instability based on direction, degree (subluxation versus dislocation),force (traumatic versus atraumatic), volition (voluntary versus involuntary), duration (acuteor chronic), and frequency (acute or recurrent). A concise approach to the complexanatomy of the shoulder, the accurate clinical diagnosis of glenohumeral instability, and thecurrent recommendations with regards to imaging the patient with instability is provided.Oper Tech Orthop 18:2-8 © 2008 Elsevier Inc. All rights reserved.

KEYWORDS shoulder, instability, anatomy, examination, imaging

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s a result of the relative lack of intrinsic stability of theglenohumeral joint, the minimal mismatch in the radius

f curvature between the glenoid and the humeral head, andhe large range of motion, the shoulder has the greatest rate ofislocations of any joint in the body.1

Because of a shallow bony socket, the stability of the shoul-er is dependent to a great extent on static and dynamicoft-tissue structures, the appropriate version of the glenoid,ts proprioceptive ability to coordinate the dynamic re-traints, and the negative intra-articular pressure.

Dynamic constraints, such as the rotator cuff (includinghe subscapularis and infraspinatus, which compress theoint), long head of the biceps, and scapular musculaturetrapezius, serratus anterior, levator scapulae, rhomboids, la-issimus dorsi) provide stability in the mid-ranges of motion.he long head of the biceps contributes to anterior shouldertability by resisting excessive external rotatory forces thatccur in the abducted and externally rotated position.2 Inddition, it plays a protective role by decreasing the stresslaced on the inferior glenohumeral ligaments.3

However, at the end ranges of motion, static constraintsuch as the glenoid cartilage, labrum, and capsule, provideost of the stability. The glenoid cartilage and labrum pro-

ide stability primarily by deepening the socket up to 50%nd decreasing humeral translation by 10% to 20%. Theabrum forms a fibrocartilaginous circumferential rim around

rthoCarolina Sports Medicine Center, Charlotte, NC.ddress reprint requests to Duong Nguyen, MD, FRCSC, OrthoCarolina

Sports Medicine Center, Morehead Medical Plaza, 1025 Morehead Med-ical Drive, Suite 300, Charlotte, NC 28204-2963. E-mail address:

hduong.nguyen@orthocarolina.com

1048-6666/08/$-see front matter © 2008 Elsevier Inc. All rights reserved.doi:10.1053/j.oto.2008.06.001

he glenoid (Fig. 1) and serves as an attachment for the bicepsnd glenohumeral ligaments.

Normal variations of the labral attachment, especiallyuperiorly, are common and include the sublabral foramenlocated in the anterosuperior quadrant of the shoulder), aord-like middle glenohumeral ligament (Fig. 2), and theuford complex (a cord-like middle glenohumeral ligamentith an absent anterosuperior labrum complex).4 The supe-

ior labrum normally inserts directly into the biceps tendonistal to where the biceps tendon attaches to the supraglenoid

ubercle (5 mm medial to the superior edge of the glenoid). Thisreates a synovial, “meniscoid-like” recess beneath the bicepsendon and the superior labrum, which should not be mis-aken for a SLAP (ie, superior labrum anterior posterior) le-ion. In general, a “lesion” that is superior to the glenoidquator is rarely pathologic.5 Inappropriate repair of theseormal variants may lead to limited external rotation postop-ratively.6

The glenohumeral ligaments are discrete capsular thicken-ngs and serve as checkreins to excessive humeral movementFig. 3). The inferior glenohumeral ligament is the majortatic stabilizer of the glenohumeral joint and consists of 3istinct parts: the anterior band, the axillary pouch, and pos-erior band.7 The most important part is the anterior band,hich is the primary restraint to anterior glenohumeral trans-

ation while the arm is in abduction and external rotation; theosition in which anterior dislocations usually occur (Fig. 4).8

he entire inferior glenohumeral ligament complex origi-ates from the anteroinferior labrum and the glenoid rim just

nferior to the middle glenohumeral ligament insertion. Withbduction, the entire complex moves beneath the humeral

ead and becomes taut. With internal rotation, the complex

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Anatomy, examination, and imaging of the shoulder 3

oves posteriorly and limits posterior translation. With ex-ernal rotation, the complex moves anteriorly and limits an-erior translation.5

The posterior band of the inferior glenohumeral ligaments less consistent than the other two bands and acts as therimary restraint against posterior translation.9 The middlelenohumeral ligament, poorly defined in up to one-third ofhe population, originates next to the superior glenohumeraligament and attaches onto the lesser tuberosity in associa-ion with the subscapularis tendon (Fig. 5). The middle gle-ohumeral ligament is under maximal tension at 45° of ab-uction and provides restraint to anterior and inferior

uxation in the midrange of abduction and external rotation.The rotator interval is the space between the superior bor-

er of the subscapularis and the anterior border of the su-raspinatus tendons (Fig. 6). In this interval runs the tendonf the long head of the biceps, portions of the superior andiddle glenohumeral ligaments, and the coracohumeral lig-

igure 1 Cadaveric view of normal labrum with surrounding mus-ulature.

igure 2 Arthroscopic view of left shoulder from the posterior portalhows a cord-like middle glenohumeral ligament (black arrow)

raping over the subscapularis (SS) tendon. s

ment. Insufficiency of the rotator interval is associated withnferior instability, which may require interval closure (refero Provencher and Saldua10).

The superior glenohumeral and coracohumeral ligamentsrovide stability to inferior translation and external rotationf the adducted arm.11 They limit posterior translation of theexed, adducted, internally rotated shoulder. The superiorlenohumeral ligament courses from the anterosuperior la-rum anterior to the biceps tendon and inserts superior to the

esser tuberosity near the bicipital groove. It is the primaryestraint to inferior translation in adduction. Although vari-ble in size, it is present in more than 90% of cases.12 Theoracohumeral ligament originates on the lateral surface of

igure 3 Anatomical drawing of glenohumeral ligaments. (Reprintedith permission.28)

igure 4 Arthroscopic view of right shoulder from posterior portal

howing anterior band of the inferior glenohumeral ligament.

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4 D. Nguyen

he coracoid as an extra-articular structure and inserts intohe greater and lesser tuberosities spanning the bicipitalroove.

athologic Lesionsankart13 first described an avulsion of the anterior inferiorlenohumeral ligament and labrum from the glenoid rim ashe essential lesion of recurrent anterior instability (Fig. 7).he Bankart lesion is found in more than 90% of first-time

raumatic anterior dislocations and may have a fleck of bonettached on avulsion. The ALPSA lesion (ie, anterior labrumeriosteal sleeve avulsion) is also pathologic and differs fromhe Bankart lesion in that the anterior glenoid periosteum isot disrupted (Fig. 8). The GLAD (ie, glenoid labrum artic-lar disruption) lesion is a detachment of the anterior artic-lar surface in association with the labrum and capsuloliga-entous structures (Fig. 9).14

The capsuloligamentous complex can avulse from the hu-

igure 5 Arthroscopic view of left shoulder from posterior portalhowing the middle glenohumeral ligament draping over the sub-capularis tendon.

igure 6 Arthroscopic view of right shoulder from posterior portal

howing rotator cuff interval. (

eral side, resulting in the HAGL (ie, humeral avulsion of thelenohumeral ligament) lesion (Fig. 10). The proper diagno-is of a HAGL lesion is critical as its presence may precluderthroscopic repairs.

Studies have confirmed that the Bankart lesion is the mostommon, but not the only, associated lesion. Other patho-ogical findings include anterior capsule insufficiency (withp to 19% plastic deformation of the inferior glenohumeral

igament), posterolateral humeral head defects (Hill-Sachsesion; Fig. 11), anteromedial humeral head defects (reverseill-Sachs lesion in a posterior dislocation), posterior gleno-umeral ligament insufficiency, rotator cuff tears, and supe-ior labrum anterior posterior (SLAP; Fig. 12) lesions.15-17

njuries to the superior labrum are important to detect be-ause the biceps tendon provides additional stability by dy-amic compression of the humeral head into the glenoidocket. Injuries to the rotator cuff are typically more common

igure 7 Arthroscopic view of left shoulder from posterior portalhowing Bankart lesion (arrow).

igure 8 Magnetic resonance imaging axial view of ALPSA lesion

arrow).

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Anatomy, examination, and imaging of the shoulder 5

fter shoulder dislocation in patients older than 40 years ofge.

Although labral lesions affect socket depth and reduce sta-ility of the glenohumeral joint, biomechanical studies havelearly demonstrated that a Bankart lesion alone is insuffi-ient to cause recurrent dislocation18 and that plastic defor-ation of the capsule occurs.19 Capsular injury may be diffi-

ult to assess during examination and arthroscopy, butailure to return the capsule to its proper tension has ofteneen cited as a cause for failure of arthroscopic repair.As many as 40% of recurrent instability patients have some

vidence of rim erosion or a missed glenoid rim fracture (Fig.3). The extent of the bony injury (ie, more than 25% of

nferior glenoid surface lost) may necessitate a bony surgicaleconstruction such as a Lartajet procedure to restore shoul-er stability. This can be assessed via a preoperative com-

igure 9 Arthroscopic view of GLAD lesion (arrow).

igure 10 Magnetic resonance imaging coronal view of HAGL lesion

arrow). s

uted tomography scan or can be seen arthroscopically withhe so-called “inverted pear-shaped glenoid.”

atient Evaluationhoulder laxity does not necessarily imply a pathologic pro-ess and must be differentiated from instability, which isaxity of the shoulder causing symptoms.5 Matsen and asso-iates initially popularized the use of the acronyms TUBStraumatic unidirectional Bankart surgery) and AMBRIatraumatic multidirectional bilateral rehabilitation inferiorapsular shift) in an attempt to classify patients with shouldernstability and provide a guide to management. Patients,owever, often fall in between these 2 categories. Alterna-ively, instability can be classified according to direction, de-ree (subluxation versus dislocation), force necessary (traumaticersus atraumatic), volition (voluntary versus involuntary), du-ation (acute or chronic), and frequency (acute or recurrent).20

igure 11 Magnetic resonance imaging coronal view of Hill–Sachsesion. (arrow).

igure 12 Arthroscopic view of left shoulder from posterior portal

howing SLAP lesion (arrow).

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istoryhe patient’s history provides valuable information re-arding the nature of the instability and associated pathol-gy. A detailed history of a traumatic event (95% of shoul-er dislocations), including arm position, direction (anteriorore common), energy level, and treatment required, is crit-

cal. The need for a closed reduction in the emergency de-artment under conscious sedation suggests a traumatic dis-

ocation that may benefit from surgical repair. Traumaticislocations are therefore more likely to cause Bankart lesionsnd Hill–Sachs lesions. Patients who dislocate with minimalrauma and in positions other than abduction and externalotation suggest multidirectional instability and associatedigamentous laxity.

Patients with anterior instability complain usually of insta-ility, not pain, in the position of apprehension (abductionnd external rotation). Patients with posterior instability typ-cally complain of instability, not pain, with the arm in flex-on, adduction, and internal rotation. A history of seizures,lectrocution, electroconvulsive therapy, and alcohol with-rawal causing delirium tremens is highly suspicious for aosterior shoulder dislocation. With inferior instability, pa-ients often complain of pain carrying heavy objects and mayeport traction paresthesias symptoms.

For patients with multiple dislocations, it is important toistinguish recurrent anterior instability from multidirec-ional instability. The former group has poorer results withonoperative treatment,21 whereas the latter often benefit

rom a shoulder rehabilitation program before attemptingurgery. Often the lines between these 2 groups are indistinctecause instability patients comprise a wide spectrum, andven those with traumatic dislocations may have increasedaxity on examination. The rate of recurrence for anterior

igure 13 Computed tomography scan axial view of glenoid rimracture (arrow).

islocations decreases with age (age �20, 90%; age 20 to 25, F

0-75%; age �40, 15%). Brief loss of control of the extremityith “paralyzing pain” is suggestive of “dead arm syndrome.”his occurs with transient anterior subluxations with the arm

n external rotation abduction and extension.Finally, the surgeon should be wary of patients who can

oluntarily dislocate their shoulders, or have psychiatric dis-rders associated with their shoulder instability as they tendo respond poorly to surgical management.

hysical Examinationthorough examination is a necessary adjunct to the history.he examination should begin with a careful examination of

he cervical spine and scapulothoracic motion. Weaknessecondary to cervical root compression and scapular wingingrom a neurologic deficit may present as shoulder instability.

Evaluation of both shoulders for comparison is essential.ssessment of muscle atrophy, deformity (loss of the deltoidontour with an anterior dislocation), location of any site ofenderness, range of motion, and strength (especially the ro-ator cuff in patients older than 40 years of age) should beerformed as for any other regular shoulder examination.imited external rotation with a prominent coracoid and an-erior acromion should alert the examiner to the possibility ofposterior dislocation.Specific instability tests are best performed supine. Recre-

ting the sensation of instability with the arm in abductionnd external rotation indicates a positive “apprehension” testanterior instability), and relief with a posteriorly appliedorce on the humerus is a positive “relocation” test. Duringhe anterior release or “surprise” test, as the arm is broughtnto abduction and external rotation, the posterior force isapidly removed and is positive if the patient has the feelingf instability.22

“Load and shift testing” (Fig. 14) in the sitting and supineosition is helpful to detect the direction of instability (ante-ior or posterior). However, this requires the cooperation andomplete relaxation of the awake patient and is often morenformative when performed under anesthesia.

Inferior laxity is assessed by applying downward tractionith the arm in adduction and external rotation, and a ‘sul-

us’ sign underneath the lateral acromion greater than 2 cm

igure 14 Load and shift testing in the supine position.

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hich does not diminish with external rotation suggests ro-ator interval insufficiency (Fig. 15).

For posterior instability, the “posterior jerk” test can alsoe performed with the arm in 90° forward flexion and max-

mal internal rotation. The examiner stabilizes the scapulaith one hand while applying a posteriorly directed force to

he patient’s arm to elicit apprehension (Fig. 16).The O’Brien’s active compression test is useful in identify-

ng SLAP tears.23 This is performed with the arm forwardexed at 90°, adducted, and internally rotated. The patient issked to resist a downward force with both the arm in inter-al rotation and in external rotation. Pain deep in the jointith internal rotation is suggestive of a SLAP tear. The com-lete shoulder examination must include assessment of neu-ovascular function (especially the axillary nerve) and testingor generalized ligamentous laxity (Fig. 17).

xamination Under Anesthesia (EUA)ombining the information obtained from history, examina-

ion, imaging and EUA together constitutes a complete pre-perative evaluation of the instability patient. EUA allows theurgeon to assess the laxity of the patient’s shoulder withoutim or her guarding and is both highly sensitive and specific

igure 15 Positive sulcus sign (distance from acromion to humeralead; horizontal black bars) indicating a pathologic rotator cuff

nterval (arrow).

igure 16 Posterior stress test to assess posterior instability. w

o findings at arthroscopy. The load and shift test is performedith the arm in 20° abduction, 20° flexion, and neutral rotation.he examiner holds the patient’s proximal humerus with oneand while applying an axial load from the patient’s elbow.nstability is assessed anteriorly, posteriorly and inferiorly.ranslation of the humerus is graded as follows: to the gle-oid rim (1�), dislocation with spontaneous reduction2�), and without spontaneous reduction (3�).

adiographic Examinationmaging should begin with plain radiographs and include annteroposterior in the scapular plane, a scapular Y view, andn axillary radiograph (Fig. 18) to confirm a concentric gle-ohumeral joint and to identify associated fractures of thelenoid and humeral head. The classic radiographic findingsf posterior instability include the loss of the humeral neckrofile or “light bulb” sign, a “vacant glenoid” sign, and annterior humeral head compression fracture (reverse Hill-achs lesion).

igure 17 Metacarpophalangeal (MCP) hyperextension: sign of gen-ralized ligamentous laxity.

igure 18 Axillary radiograph demonstrating posterior dislocation

ith reverse Hill-Sachs lesion (arrow).

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8 D. Nguyen

An anteroposterior radiograph in internal rotation bestemonstrates Hill–Sachs compression fractures of the poste-ior–superior humeral head. A Stryker notch view (10° ce-halic tilt centered on the coracoid with the hand on top ofhe head with the patient supine) also is useful for identifyingill–Sachs lesions, whereas a West Point view (modified ax-

llary lateral view with the patient prone and the beam an-led 25° inferiorly and medially) reliably demonstratesony Bankart lesions.24

To better quantify the size and location of bony defects andlenoid erosion (chronic instability), a computed tomogra-hy scan is recommended, which also allows for assessmentf glenoid version and to rule out glenoid hypoplasia. Mag-etic resonance imaging is excellent for evaluating the rotatoruff and other soft tissue. The addition of gadolinium (ie,agnetic resonance arthrography) increases the sensitivity

nd specificity of the scan and is recommended for a moreccurate diagnosis of labral injury.25-27

onclusionhe combination of a thorough understanding of the dy-amic and static stabilizers of the shoulder, a careful andomplete history and physical examination, and the orderingf the appropriate imaging tests will help the surgeon deciden the optimal management for the patient with instability.he particular treatment chosen will depend on the accuratelassification of the instability based on direction, degreesubluxation versus dislocation), force necessary (traumaticersus atraumatic), volition (voluntary versus involuntary),uration (acute or chronic), and frequency (acute or recur-ent).

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