CHAPTER 3 Shoulder EPIDEMIOLOGY OF SHOULDER PAIN SHOULDER PAIN IN THE GENERAL POPULATION Prevalence • 20% (1%–67% depending on studies) in the general population • 1% of adults have disabling shoulder pain (in the United Kingdom; it may vary depending on the definition) (1) • More common in women, middle-aged and elderly, smokers, those with previous trauma, and wheelchair users • Common in 50- to 56-year-olds (may be due to normal aging process of the rotator cuff) and in 12- to 18-year-olds (possibly due to computer and mouse use) SHOULDER PAIN IN ATHLETES (2) Prevalence • Varies, 3% to 8% in athletes overall and up to 60% in overhead throwing sports, swimming, or volleyball • Shoulder: most injured body part in swimmers, third most common (MC) injured area in volleyball players • Increases with the level of activity and competition (3) • Signs suggestive of impingement syndrome and instability: very common among athletes Risk factors • Overuse/trauma, abundant soft tissue, sports requiring precise neuromuscular coordination • SICK scapula syndrome: scapular malposition, inferior medial border prominence, coracoid pain/malposition and scapular dyskinesia (SICK), more common in overhead athletes (4) • Tendon overuse, instability, and trauma in younger athletes versus degenerative changes: mainly in older athletes SHOULDER PAIN AT WORK (5) Prevalence • Common in the workplace, but less commonly caused by work (13% of all shoulder problems presenting to primary care providers are work related) Risk factors • High risk for shoulder problems: workers using upper limbs. For example, welders, musicians, sign and brick layers, and workers with pneumatic tools • Increasing shoulder-related disorders in those who work with computers; especially in younger population • No readily identifiable cause Workplace modifications • No effective ergonomic approaches focusing on primary prevention of shoulder pain at work • Early return to work likely to have best chance of good vocational outcome DIFFERENTIAL DIAGNOSIS MUSCULOSKELETAL (MSK) CAUSES OF SHOULDER PAIN BASED ON LOCATION (FLOWCHART 3.1) Surface anatomy (Figure 3.1) • Anterior and lateral • Posterior • Superiorly: acromioclavicular (AC) joint FIGURE 3.1 Surface anatomy of the shoulder (A) anterior and (B) posterior aspect of the shoulder region. FLOWCHART 3.1 Differential diagnosis of musculoskeletal shoulder pain. REGION ANATOMIC STRUCTURE COMMON MSK DISORDERS Antero-Lateral Subacromial space (1 in Figure 3.2) Subacromial impingement syndrome • Subacromial/subdeltoid bursitis: constant shoulder pain and night pain • Rotator cuff (supra/infraspinatus) tendinopathy/tear: pain with movement (rather than constant). Calcific tendinitis: can be severe, constant temporarily Superior Acromioclavicular joint (3 in Figure 3.2) Degenerative, trauma, distal clavicular osteolysis, and infection Sup. labrum/supraglenoid tubercle Superior labral tear from anterior to posterior (SLAP): often asymptomatic Antero-medial Bicipital groove (2 in Figure 3.2) Bicipital tendinitis and biceps tendon subluxation and tear • Location of tenderness (on bicipital groove) changes with external/internal rotation Coracoid process/subcoracoid space Subcoracoid impingement syndrome Pain/tenderness immediately lateral to coracoid process Subscapularis Tear, tendinosis, subscapularis bursitis • Pain on resisted internal rotation (often not specific) Medial Sternoclavicular joint (5 in Figure 3.2) Degenerative changes (6), trauma, or infection • Pain on the joint with shoulder movement (especially cross-arm adduction) Posterior Posterior edge of the acromion (6 in Figure 3.2) Shoulder impingement; external (subacromial bursitis) Internal impingement between humeral head and glenoid Rotator cuff (infraspinatus) tendinitis/tear, calcific tendinopathy Posterior subluxation of glenohumeral joint; often asymptomatic Medial scapular border Myofascial pain syndrome of rhomboids, trapezius Scapulothoracic bursitis Suprascapular notch (7 in Figure 3.2) Suprascapular N entrapment at suprascapular notch: both supra and infraspinatus muscles involved • Spinoglenoid notch: infraspinatus muscle atrophy (often without pain) Poorly localized Glenohumeral joint (4 in Figure 3.2) Adhesive capsulitis (often diffuse, poorly localized pain), glenohumeral arthritis (OA, inflammatory arthropathy), osteonecrosis, glenoid labral tears, and fracture Quadrilateral space (8 in Figure 3.2) Axillary nerve entrapment (7) MSK, musculoskeletal; OA, osteoarthritis. FIGURE 3.2 Bony anatomy of the shoulder. NEUROPATHIC CAUSES OF SHOULDER PAIN C5, 6 radiculopathy: neck pain more significant than shoulder pain ± sensory (paresthesia, tingling, rarely numbness) and motor symptoms Brachial amyotrophy: initial severe pain (≥7/10, improved) followed by rapid/significant atrophy and weakness ± persistent sensory symptom Suprascapular neuropathy: may be isolated atrophy (supra/infraspinatus) ± pain (deep, posterior) Axillary neuropathy (at quadrilateral space): atrophy (deltoid and teres minor) ± pain (deep) Mimickers: Myofascial pain syndrome of scapular stabilizer muscle (trapezius, rhomboids, levator scapular etc) with referred pain and cervical facet arthropathy (spondylosis, whiplash, worse with extension/rotation) EXTRINSIC CAUSES OF SHOULDER PAIN (8) • Myofascial pain syndrome of neck (paraspinal/suboccipital) muscles (referred pain) • Hepatobiliary disease • Diaphragm irritation and pneumonia (atypical pneumonia), and apical lung tumor • Metastasis; consider if + risk factors, for example, elderly smoker • Coronary artery disease with known cardiovascular (CV) risk factor NEUROLOGICAL SYMPTOMS Sensory symptoms (Flowchart 3.2) • Cervical spine disease (radiculopathy, facet arthropathy), brachial plexopathy (diabetic amyotrophy; radiculoplexusneuropathy), suprascapular, axillary neuropathy (positive or negative symptoms), or cerebrovascular accident (CVA; stroke, if + CV risk factors) • Myofascial pain (with paresthesia, positive sensory, or autonomic symptoms): negative symptoms (numbness) are rare Motor symptoms • Weakness and fatigue • Weakness from MSK disorders: both active and passive range of motion (ROM) involved FLOWCHART 3.2 Differential diagnosis of neuropathic shoulder pain. • Neuromuscular disorders: passive ROM intact unless secondary contracture/stiffness or concomitant MSK lesions exist • Psychogenic: distraction results in inconsistent findings SNAPPING SHOULDER Differential diagnosis based on location (9–11) • Scapulothoracic articulation (posterior) • Anterior snapping (12) SHOULDER INSTABILITY Differential diagnosis based on etiology • Traumatic: soft tissue (capsule, ligament, tendon/muscle) versus bony (Hill–Sachs or bony Bankart lesion) • Atraumatic: multidirectional instability, neurological (unbalanced muscle pattern: lower motor neuron disease, muscle disease or upper motor neuron disease), generalized laxity Differential diagnosis based on location • Anterior instability: MC (≥95%), violent shoulder external rotation/ abduction, fall on outstretched hand • Posterior: landing on forward flexed and adducted arm above shoulder level ANATOMY BONE, JOINT, AND LIGAMENT Humerus • Head and tuberosity • Bony landmarks (useful for imaging interpretation or MSK ultrasound [US] scanning) • Vascular supply: (13) Scapula • Suprascapular notch • Spinoglenoid notch; adjacent to the posterior GH joint; cyst/ganglion in the spinoglenoid notch often originating from labral lesion at the posterior GH joint • Scapular tilt: ~30° from coronal plane (lateral side anterior than medial side) Glenohumeral (GH) Joint • Glenoid faces posteriorly (~7°) and upward (~5°) • Labrum • GH ligament Acromioclavicular (AC) joint • A diarthrodial joint with a meniscal homolog (fibrocartilaginous disk: degenerate after 40 years) • An inherently unstable articulation • Static stabilizers: AC joint capsule/ligament and the CC ligament (stronger than AC ligament) – Aggressive distal clavicle excision (DCE) can destabilize the AC joint and lead to symptomatic posterior impingement against the acromion – The conoid ligament: more posterior than trapezoid (important for support against superior displacement) – The trapezoid origin on the mid-portion of the inferior surface of the clavicle • The dynamic stabilizers: the deltoid and trapezius muscles • AC joint innervated by suprascapular, axillary, and lateral pectoral nerve Sternoclavicular (SC) joint (14) • Diarthrodial joint, the articular surfaces of the SC joint covered in hyaline cartilage with an interposed fibrocartilaginous disc and highly incongruent FIGURE 3.3 Glenoid cavity of the scapular and glenohumeral stabilizers (view from the anterolateral aspect). • A “saddle” (convex in the AP plane, concave in the vertical plane) shape in clavicle and smaller convex shape of the manubrium • Unstable joint: only half of the medial clavicle articulates with the sternum – Consists of anterior and posterior fasciculi with an interposed bursa – A “twisted” appearance and stability is achieved during rotation and elevation of the distal clavicle Subacromial/coracoacromial arch space (15) • Borders of subacromial space Subcoracoid space • The normal coracohumeral interval, defined as minimal distance between the coracoid process and lesser tuberosity, is in the range of 8.4 to 11 mm • Involves subscapularis muscle/tendon, subcoracoid bursa and GH joint capsule (16) • Subcoracoid stenosis: if coracohumeral interval <6 mm. Contribute to subcoracoid impingement syndrome Rotator cuff interval (17) • Between inferior edge of the supraspinatus and the superior edge of the subscapularis • Functions • Clinical implications FIGURE 3.4 Nerve innervation around the shoulder joint and common entrapment sites (A) posterior aspect and (B) anterior aspect. NERVE (18) Sensory innervation of the human shoulder joint and capsule (19; Figure 3.4) • Ventral: lateral pectoral, subscapular, axillary, and musculocutaneous N • Dorsal: suprascapular and axillary N • Suprascapular N BURSA Subacromial subdeltoid bursa (20) • The largest bursa in the body (21) • Innervated by suprascapular N. posteriorly and lateral pectoral nerve anteriorly • Contains pressure sensitive Pacinian corpuscles and Ruffini endings (mechanical and pressure sensitive) • Pain correlates with pro-inflammatory markers, cytokines, and substance P in the bursal tissue (6) Subcoracoid bursa (22) (Figure 3.2) • Located under the coracoid process and the conjoint tendon (of the biceps short head and coracobrachialis), superficial to the subscapularis, and minimizes the friction between the coracoid and the subscapularis tendon • The subcoracoid bursa occasionally communicates with the subacromial bursa • It merges with the superior subscapularis recess known as subscapularis bursa (under the subscapularis) in ~30% Other bursae around the scapula (23,24) MAJOR/ANATOMIC BURSAE Infra-serratus bursa Between serratus anterior and the chest wall Inferior angle of scapula Supra-serratus bursa Between subscapularis and serratus anterior Scapulo-trapezial bursa Between superomedial scapular and trapezius MINOR/ADVENTITIAL BURSAE Superomedial angle of scapula Infraserratus and supraserraus bursae Inferior angle of the scapula Infraserratus bursae Spine of scapula; trapezius Between medial spine of scapula and trapezius • Scapulothoracic bursa: commonly seen in overhead throwing athletes especially bursa at the inferior angle (pitching), weight training, swimming, gymnastics, football, or local trauma MUSCLE GH movement • Humerus on the glenoid of the scapular; rotator cuff muscle with other extrinsic muscles • Pectoralis major and latissimus dorsi: large muscles to adduct and medially rotate the humerus (compared to the small external rotator. Rationale for external rotator strengthening to balance, target for spasticity management) • Deltoid: all motion of the shoulder Scapulothoracic movement (scapula on the trunk/ribs) SHOULDER MOVEMENT (26,27; FIGURE 3.5) • GH and scapulothoracic joint motion together to achieve the abduction movement • Normal shoulder abduction requires scapula rotating upwardly and externally, and tilting posteriorly FIGURE 3.5 Scapular plane and angle of torsion. • Abduction requires external rotation to clear the greater tuberosity from impingement SUBACROMIAL IMPINGEMENT Decreased distance between humerus and coracoacromial arch • Supraspinatus tendon tear: elevates the humeral head to the coracoacromial arch (vicious cycle) • Scapular stabilizer weakness; scapula protracts and depresses the acromion • Scapular protraction and anterior tilting of the scapular common in impingement syndrome Peak forces under acromion: occur between 85 and 135° of elevation (≈painful arc sign) Main area of increased contact: anteroinferior part of the acromion (hooked or curved shape) • The subacromial space is decreased when the anterior aspect of the acromion is more prominent SUBCORACOID IMPINGEMENT: ROLLER WRINGER EFFECT (28) • The coracoid process impinges on the superficial surface of the subscapularis tendon, applying a tensile load (stretch) to the deep surface or undersurface of the tendon SUPRASCAPULAR NERVE TRACTION WITH SCAPULA POSITION • Sling effect: under the suprascapular ligament • Scapular protraction and abduction: increased distance between the cervical spine and suprascapular notch (especially if tethering exists) BIOMECHANICS OF THROWING (29; FIGURE 3.6) PHASE ENGAGED MUSCLES POTENTIAL INJURIES Windup Rotator cuff muscles: inactive during this phase Cocking Early cocking: deltoid Late cocking: high torque with supra/infraspinatus/teres minor activation Anterior subluxation, internal impingement, glenoid labrum lesions Increased risk with glenohumeral internal rotation deficit Acceleration Triceps: early activation Late muscle activation • Pectoralis major • Latissimus dorsi • Serratus anterior Shoulder instability Labral tears Overuse tendinopathy Tendon rupture Release and deceleration Eccentric contraction of all muscles is required to slow down arm motion Highest torque phase Most harmful Labral tear (especially with biceps anchor, type 2 SLAP lesion) Subluxation of the long head of the biceps by tearing of the transverse ligament Lesions of the rotator cuff (teres minor), such as undersurface tears or tensile overload Follow-through Labral tear (with biceps anchor, type 2 SLAP lesion) Abnormal glenohumeral kinematics caused by tight posterior glenohumeral joint structures forcing the humeral head anteriorly and superiorly into the acromial arch during this phase SLAP, superior labral tear from anterior to posterior. FIGURE 3.6 Six phases of the baseball pitch. SHOULDER STABILITY (30) Static stabilizer (see Figure 3.3) • Position of glenoid: face posteriorly and superiorly (cephalad) • Joint capsule and negative IA pressure • Labrum: deepens glenoid by 50% • GH ligament Dynamic stabilizer (more important) • Rotator cuff muscles, biceps, triceps, deltoid, and scapular stabilizer PHYSICAL EXAMINATION INSPECTION Scapular position • On seated and standing and inspect scapular positioning after undressing • Asymmetry of the scapula or prominent medial border and inferior angle: winging of scapula • Less common causes • Normal variant: throwing athletes have slight depression of the scapular in the dominant side Other physical findings • Scar, ecchymosis, erythema, rashes, deformities, shoulder height, etc • If spine of scapula is visible; consider possible muscle atrophy of either supra/infraspinatus or trapezius M • Atrophy • Swelling: often difficult to recognize the swelling depending on the body habitus PALPATION Bony landmarks • On sitting with forearm neutral • Anterior: bicipital groove (often difficult to palpate), lesser tuberosity (subscapularis, externally rotate to expose, orthogonal to the medial epicondyle), and greater tuberosity (supraspinatus insertion, usually same plane with lateral epicondyle) • Superior: AC joint (palpation with gradual flexion or extension of the arm) • Posterior: scapular (resting position: medial border; ~3 inches from the midline, superior angle of scapular; second rib and inferior angle; seventh rib), spine of scapula: third thoracic vertebra, GH joint • Medial: SC joint; clavicle protruded normally Trigger points • Look for specific referred pain pattern (see Figure 2.3 in Neck section) RANGE OF MOTION Normal and functional ROM (31) (see following table) Apley “Scratch test” • Abduction and external rotation (ABER) to reach opposite scapula: be cautious in patients with anterior subluxation/instability) • Adduction and internal rotation to reach the inferior angle of the scapula: pain in impingement syndrome Normal scapulothoracic motion and GH joint articulation • GH painful arc: 45 to 60° to 120° (when surgical neck strikes the acromion; full abduction is possible when humeral external is rotated), usually at 85°, AC joint painful arc: 170 to 180° abduction • Cautious of trunk rotation when evaluating shoulder ROM (eg, trunk rotation instead of shoulder externally rotation) GH internal rotation deficit • Loss of internal rotation >30 to 40° relative to the expected gain in external rotation, compare it to the opposite site, common in overhead throwers • Tight posterior capsule and anterior capsule stretched • Associated with internal impingement, GH instability, and increased incidence of SLAP lesion • Check the AC joint (AC sprain) and SC movement/pain and pain on GH joint movement STRENGTH OF ROTATOR CUFF MUSCLES Supraspinatus • Open (full) can test: resisted abduction with thumb up rather than thumb down • Jobe’s test: resisted abduction to 90° on the scapular plane; with ~30° tilt (anteriorly) from frontal plane and thumb down (internally rotate the arm): often limited with pain from impingement Infraspinatus • Resisted arm external rotation Teres minor • Resisted arm external rotation with the arm in 90° abduction Subscapularis • Arm internal rotation with elbow at side in 90° flexion • Lift off test: hand brought around back to region of lumbar spine, palm facing outward SPECIAL TESTS (32) NAME DESCRIPTION SENSITIVITY (SEN) AND SPECIFICITY (SPE) IN % Subacromial Impingement Test (33) Neer’s test Stand behind the patient and passively elevate the arm in the scapular plane while stabilizing the scapula. Positive with pain elicited in the arc between 70–120° Sen: 75–88 Spe: 31–51 Hawkins’ test The patient is examined in sitting position with shoulder forward flexion at 90° and elbow flexed to 90°, supported by the examiner. The examiner then stabilizes scapular holding the spine of scapula while internally rotating the arm. Positive with pain or symptom reproduction More specific for impingement under the coracoacromial arch Sen: 83–92 Spe: 38–56 Empty can To assess the deltoid and supraspinatus M strength as well as impingement With the arm at 90° of abduction and neutral rotation, the shoulder is then internally rotated on scapular plane with the thumb down. Apply downward force against resistance. Check side to side Sen: 18–79 Spe: 38–100 Painful arc Actively elevate the arm in the scapular plane until full elevation is reached then bring the arm down in the same arc. Positive if pain or painful catching occurs between 60° and 120° of elevation (34) Sen: 60–70 Spe: 40–80 Drop arm test The examiner abducts the patient’s shoulder to 90° and then asks the patient to slowly lower the arm to the side Positive if the patient is unable to return the arm to the side slowly/smoothly or has severe pain when attempting to do so Sen: 10–25 Spe: 70–80 PPV: 100 + Hawkins’, painful arc test, decreased infraspinatus M strength: very high likelihood for impingement + Drop arm test, painful arc test, decreased infraspinatus M strength: likelihood ratio of 15 for full-thickness tear Glenohumeral Instability The apprehension test The patient in the supine position and the involved shoulder in 90° of abduction, the arm is externally rotated beyond 90° Positive when the patient is apprehensive or feels as if shoulder will dislocate as the humeral head begins to subluxate anteriorly Sen: 69 Spe: 50 The relocation test Patient with shoulder in 90° abduction and external rotation (apprehension position), a posteriorly directed force applied on the humerus. Positive if the sensation of apprehension is relieved (Fowler’s sign) (35) Sen: 30–68 Spe: 44–100 The sulcus sign Apply axial downward traction with the arm at the side. Positive if a gap is observed between the humeral head and anterior-inferior aspect of the acromion indicating multidirectional instability High false positive in asymptomatic patients Sen: 90 Spe: 85 Anterior and posterior drawer tests Patient supine and the arm abducted to 45°, neutral rotation, and elbow flexed. The examiner grasps the proximal arm at the deltoid insertion and stabilizes the limb by grasping the patient’s wrist with the opposite hand. Grade 0: mild translation (0%–25%), grade I: 25–50%, grade 2: reducible translation over the rim (50%), and grade III: locking of the humeral head over the rim High false positive (up to 50%) (36) Sen: 20–50 Spe: 70–80 in traumatic anterior instability (37]) Load and shift test The patient is seated or standing with the arm to be tested fully relaxed at the side. While stabilizing the scapula with one hand, the examiner grasps the proximal humerus with the other hand and applies force anteriorly and posteriorly. The degree to which the humeral head shifting over the anterior and posterior glenoid rim is measured. Comparison with the contralateral side for side-to-side variation (32). Sen: 91 Sep: 93 Biceps Tendon Speed test Resisting shoulder flexion with the elbow fully extended and supinated Positive if pain is generated in the bicipital groove Higher sensitivity and specificity for anterior SLAP lesion (38) Sen: 68–90 Spe: 13–55 Yergason test With the elbow pronated and flexed at 90°, the examiner resists the patient’s attempt to supinate and externally rotate the arm, while palpating the bicipital groove Positive if dislocation of the biceps tendon is felt or pain occurs in the bicipital area without dislocation Sen: 37 Spe: 86 Ludington test Place both arms behind the head and isometrically contract the biceps Positive if pain or subluxation is reproduced The “Popeye” sign indicates biceps tendon rupture SLAP lesion O’Brien test With the arm forward flexed to 90°, adducted 10–15°, and maximally internally rotated (thumb down), the examiner applies a downward force to the fully extended arm Positive if pain or clicking is “inside” the shoulder and pain is reduced with the arm maximally supinated No relief of pain in maximally supinated Sen: 32–100 Spe: 13–98.5 Anterior slide test Place the patient’s hands on lateral hips with the elbows facing posteriorly The examiner stabilizes the scapula with one hand, and with the other hand placed on the patient’s elbow, applies an anteriorly and superiorly directed force to the arm Positive with pain, pop, or click in the anterior shoulder (40) Sen: 8–78 Spe: 84–91 Crank test With the patient standing or supine, the arm is elevated to approximately 90° in the scapular plane, and the elbow is flexed. While applying an axial load to the humerus with one hand, the examiner’s other hand maximally internally and externally rotates the arm Positive predictive value: 94%, negative predictive value: 90% (41) Sen: 46–91 Spe: 56–100 Clunk test Compression-rotation The patient is supine with arm fully abducted. The examiner circumducts the humeral head in an attempt to entrap a torn labral fragment. One of the examiner’s hand is placed posterior to the humeral head to apply anterior pressure while the other hand is placed at the level of the humeral condyles to provide rotation and axial loading Sen: 80 Spe: 19–49 The Kim test for posteroinferior labral lesion To evaluate posterior instability (posterior inferior labral lesion) Patients are seated and shoulder is abducted to 90° and then moved to 45° forward diagonal flexion while simultaneously applying a downward and posteriorly directed force to the upper arm and pushing the elbow towards the shoulder joint (42) Positive if a sudden onset of posterior shoulder pain occurs Sen: 90 Spe: 94 Acromioclavicular Joint Cross arm adduction test Shoulder is positioned in 90° of forward flexion and is forcefully adducted across the body toward the opposite shoulder. Positive with reproduction of patient’s pain Sensitive to shoulder impingement syndrome (sensitivity: 82, specificity: 27.7) (43) Sen: 77 Spe: 79 Paxinos test Places the thumb over the posterolateral corner of the acromion and the index and long fingers of the ipsilateral or the opposite hand superior to the mid portion of the ipsilateral clavicle Then, the examiner applied pressure to the acromion with the thumb, in an anterosuperior direction, and inferiorly to the midpart of the clavicular shaft with the index and long fingers Positive if pain is felt or increased pain in the AC joint Sen: 79, Spe: 50(44) Thoracic Outlet Syndrome Roo’s test With the forearms flexed to 90°, the arms laterally abducted to 90° and externally rotated, the patient opens and closes the hands every 2 seconds for 3 minutes. Positive if the symptoms are reproduced, if the patient is unable to maintain the position, or the radial pulse is diminished Adson maneuver The radial pulse is palpated as the patient inspires while maintaining the symptomatic extremity at the side, the neck hyperextended, and the head rotated toward the symptomatic side Positive for vascular thoracic outlet syndrome with alteration or obliteration of the radial pulse or change in blood pressure. Often positive in healthy asymptomatic persons Wright maneuver The radial pulse is palpated while the symptomatic limb is held overhead and abducted (to 180°) with the elbow flexed and the upper extremity externally rotated. This position is maintained for 60 seconds. Positive if the patient’s symptoms are reproduced (may be more sensitive in the lesion between the pectoralis minor and rib cage) PPV, positive predictive value.
Coracoid process: 1 inch below the clavicle (at the junction of middle and lateral thirds)
Greater tuberosity of humerus: same coronal plane as the lateral epicondyle of the elbow, lesser tuberosity; anteromedial to greater tuberosity (expose with external rotation)
Spine of scapular medially (at T3: root of the spine of scapular), superior angle: T2, inferior border of scapular: T7 level, medial border of scapular depending on the protraction and retraction; about 2 to 3 inches in anatomic position (from midline at T3)
Risk factors: age, smoking, or constitutional signs/symptoms
Tendon tear/rupture with pain
Mild weakness unless multiple tendons and muscles are involved. Supraspinatus; minimal contributor to abduction (compared to deltoid muscle)
Two heads of biceps brachii; long and short head. One tendon head rupture does not necessarily cause significant weakness
Isolated weakness without pain (or minimal pain): decreased ROM presents
Adhesive capsulitis (after initial painful stage, decreased range of motion prominent), massive rotator cuff tear, and joint deformity with contracture
Osteoarthritis with decreased ROM: global decrease, including external rotation (less severe than adhesive capsulitis)
Lower motor neuron disease: cervical (C5–6) radiculopathy, brachial plexopathy, axillary neuropathy, suprascapular neuropathy, rarely motor neuron disease (amyotrophic lateral sclerosis [ALS], spinal muscular atrophy)
Significant weakness and atrophy present
Upper motor neuron disease: stroke, brain lesion (tumor, inflammation, infection, vascular), cervical myelopathy (distal part of extremity than proximal part, inflammatory; multiple sclerosis [MS], tumor, infection, vascular, and idiopathic), ALS
Muscle disease: minimal sensory symptoms although concomitant lesions or pain (myalgia) can occur with weakness
Hereditary (facioscapulohumeral muscular [FSH] dystrophy, myotonic dystrophy) and acquired (polymyositis, dermatomyositis, necrotizing myopathy, etc)
Polymyalgia rheumatica: older adults, usually bilateral, with myalgia
Scapulothoracic dyskinesia with scapulothoracic bursitis, muscle atrophy (from nerve injury or disuse)
Rotator cuff tendinopathy, tear, and glenohumeral (GH) joint pathology (labral tear, loose body)
Bony abnormalities
Structural spinal deformities (including scoliosis and thoracic kyphosis)
Luschka tubercle (6%, a hook-shaped prominence on superomedial angle of scapula)
Tumor (including osteochondromas of the rib and scapula; MC benign tumor of the scapulae)
Healing fractures of ribs or scapulae with bony angulation or exuberant callus
Tuberculosis, syphilitic lesions
GH instability
Labral tears and intra-articular (IA) loose body (GH joint)
Chondral or osteochondral lesions
Bicipital tendon instability and subscapularis tendinopathy
Bursopathy: subcoracoid bursitis and calcific bursitis
Often voluntary, associated with posterior Bankart lesion, and capsular laxity
Anatomic neck (distinction between the tuberosity and humeral head, 6 mm above greater tuberosity)
Lost (flattened) in bony impingement (eg, rotator cuff arthropathy)
Neck and shaft inclination: 145° (130–150), angle of inclination
Humeral condyle (distal) and head angle; 30°; angle of torsion
Increased angle of torsion in retroversion (with decreased external rotation of GH joint in examination) and decreased in anteversion similar to the hip
Clinical implication: positive relationship between increased humeral torsion and recurrent anterior dislocation of shoulder
Greater tubercle has three facets for rotator cuff tendons (supraspinatus/infraspinatus/teres minor): from anterior/superior to lateral/inferior: upper, middle, and lower facet
Lesser tubercle: subscapularis
Intertubercular (bicipital) groove: biceps long-head tendon in the groove and distally attachment for tendons from laterally to medially (pectoralis major/latissimus dorsi/ teres major)
Deltoid tubercle for deltoid M insertion anteriorly, posteriorly spiral groove for radial N located in the middle of the humerus
Anterior circumflex artery; lateral to the biceps long-head tendon; avoid during injection to bicipital groove above surgical neck, main supplier to the humeral head (with posterior circumflex A)
Cautious of injury during rotator cuff surgery and open reduction
Suprascapular nerve traverses from anteromedial to posterior-inferior-lateral direction
Variant; ossified suprascapular ligament 
suprascapular foramen; vulnerable to develop suprascapular neuropathy; supra and infraspinatus muscles involved
Isolated infraspinatus muscle involvement
If angle decreased 
increased risk of recurrent anterior subluxation/dislocation
Wedge-shaped fibrocartilage rim attached to glenoid fossa
Superior and anterosuperior portion: less vascular; may be more vulnerable to pathology
Superior: biceps long head (to the supraglenoid tubercle)
Inferior GH ligament: attaches to labrum and glenoid
Function: deepens glenoid cavity by 50% (passive stabilizer) and serves as an anchor point (GH ligament and biceps long-head tendon)
Superior GH ligament: superior labrum near biceps to superior part of lesser tuberosity (rotator cuff interval), resists posterior and inferior translation
Medial GH ligament: most variable, resists anterior translation
Inferior GH ligament: runs mediolaterally from the 3 o’clock to 9 o’clock position and resembles a hammock
Primary restraint of anterior-posterior translation in the abducted shoulder (especially 90° ABER [abduction and external rotation])
AC ligament
Prevent horizontal plane motion
The ligament inserts an average of ~18 mm medial to the AC joint on the clavicular undersurface
The coracoclavicular (CC) ligaments
Prevent inferior migration of the scapulohumeral complex relative to the clavicle
If the AC ligaments are disrupted, the CC ligaments compensate by providing significant restraint to anteroposterior (AP) displacement
Composed of the conoid and the trapezoid ligament
ROM around the SC joint: nearly freely movable in all planes
35° of elevation, 35° of AP motion, 50° of rotation around its long axis
30° of rotation with shoulder elevation
Stability by ligament; the capsular ligament, the IA disc ligament, the interclavicular ligament, and the costoclavicular ligament
The capsular ligament is composed of anterior and posterior segments (stronger than anterior resisting superior translation of the medial clavicle)
The IA disc ligament resists medial displacement with compression
The interclavicular ligament resists superior migration of the medial clavicle
The costoclavicular ligament (also known as the rhomboid ligament) is the strongest of the SC ligaments
The superior border (the roof): the coracoacromial arch—the acromion, the coracoacromial ligament, and the coracoid process
The inferior (the floor): the greater tuberosity of the humerus and the superior aspect of the humeral head
The space between the acromion and the humeral head: 1.0 to 1.5 cm
Containing the rotator cuff tendons, the long head of the biceps tendon, the subacromial/subdeltoid bursa, and the coracoacromial ligament
The true height of this space is considerably less than that seen on radiographs (soft tissue is not visualized)
The impingement zone: centered on the insertion of the supraspinatus tendon on the greater tuberosity
Impingement by the anterior one-third of the acromion, the coracoacromial ligament, and the AC joint rather than by just the lateral aspect of the acromion
Medial: superficial; coracohumeral ligament (CHL), deep; superior GH ligament (SGHL) and joint capsule
Lateral: four layers
First layer: superficial CHL fan to subscapularis and supraspinatus tendon
Secondary layer: subscapularis and supraspinatus
Third layer: deep CHL
Fourth layer: SGHL and lateral capsule
Resistance to inferior and posterior translation of the humeral head (especially in flexed, abducted, and external rotated shoulder)
Prevents excessive flexion, extension, adduction, and external rotation
Increases stability of long head of biceps tendon
Limits excessive GH motion
Rotator cuff interval (RI) contracture: thickened and fibrotic RI capsule and CHL
Adhesive capsulitis: may be significant inflammation on the bursal side of the RI
RI laxity: pain and instability (anterior shoulder instability)
Articular (afferent sensory) branch from CHL, AC ligament and joint, GH joint, and subacromial bursa ± cutaneous branch in proximal lateral arm (5/35 in cadaver study)
Proprioception and nociception (free nerve endings, A ð and C fibers)
Patients with inflammatory cells: constant shoulder pain and pain at night
Patients without inflammatory cells: pain only with movement
Minimizes the friction of the superficial fibers of the subscapularis against the coracoid
Pain under the scapular, crepitus, grinding, and snapping with/without pain
Flexion: anterior deltoid, extension: posterior, abduction: middle, adduction: ant + post, internal rotation: anterior, external rotation: posterior
Decreased GH joint movement compensated by excessive scapulothoracic movement: often underrecognized and it can cause secondary myofascial pain in the scapular stabilizer
Protracted scapular decreases subacromial space by decreased upward rotation and decreased posterior tilt of scapula 
promoting impingement syndrome
In GH instability: decreased upward rotation and increased internal rotation of scapula
Decreased external rotation (in GH arthritis and adhesive capsulitis) limit abduction
tensile undersurface fiber failure
Superior, middle, inferior GH ligament
Inferior GH ligament: primary restraint of anterior-posterior translation in the abducted shoulder (especially 90° ABER)
Proprioception by joint capsule
Muscle contraction: dynamic joint constraint (but can be joint dislocator from imbalance)
With rotator cuff tear, deltoid during arm elevation: increased joint reaction force to the superior and anterior direction (impingement and anterior instability)
Brachial plexus injury: Erb’s palsy (arm internally rotated and adducted, “waiter’s tip”)
Sprengel’s deformity: undescended scapular
Significant atrophy with weakness (in relative short time): consider neuromuscular causes (disuse atrophy in chronic rotator cuff tears, not dramatic)
With trauma/acute event: traumatic root avulsion, radiculopathy, brachial plexopathy, suprascapular N injury or other mononeuropathy, and chronic tendon rupture
Without trauma: brachial amyotrophy or diabetic/nondiabetic radiculoplexus neuropathy
Symmetric atrophy or winging: limb girdle muscular dystrophy, fascioscapulohumeral muscular dystrophy, acquired myopathy, and peripheral neuropathy (diabetes [DM] cachexia), etc
Asymmetric: DM amyotrophy, cervical radiculopathy, suprascapular neuropathy: infraspinatus atrophy if lesion is at spinoglenoid notch
Often indicated by loss of clear bony landmark in lean person
Joint effusion; usually subtle vs bursal effusion; more prominent, or symptomatic on either impingement position or direct palpation
Internal/external rotation will help to differentiate the tuberosity vs fixed acromion/coracoid
Antero-medial: coracoid process (about an inch below the clavicle)
Anterolateral: supraspinatus insertion
Palpate the dislocation and gap of the joint (may be difficult to palpate the gap with effusion and osteophyte; bump)
Start palpation from medial one-third of the clavicle
If paradoxical, exaggerated scapulothoracic movement 
adhesive capsulitis and GH osteoarthritis
Test patient’s ability to lift hand away from back (internal rotation). Confounded by other muscles. More accurate if the tested hand can reach the contralateral scapula
suggests AC joint pathology (39)
Positive with pain, pop, or clunk
Positive with clunk or grinding reproducing the patient symptoms
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