Shoulder girdle includes scapula, proximal humerus, lateral clavicle, and associated muscles/connective tissue.
Pseudocyst of the humerus – Normal variant, increased cancellous bone in region of greater tuberosity (more lucent), may mimic lytic lesion esp with hyperaemia and disuse. May be hot on bone scan due to hyperaemia.
Absent/lucency of distal clavicle:
- Posttraumatic osteolysis
- Metastases, myeloma
- Cleidocranial dysplasia
Imaging Techniques and Applications
- AP shoulder
- Axial/axillary view – CC beam in abduction with XRT under shoulder.
- Trans-scapular Y view – Beam parallel to scapula with patient ~45deg oblique, hand on opposite shoulder. Head superimposed on glenoid with spine posterosuperior, coracoid anterosuperior, scapular body inferior.
- AP external rotation – Greater tuberosity lateral, articular surface medial, lesser tuberosity over centre.
- AP internal rotation – Rounded contour with greater tuberosity projecting over the humeral head.
- True anatomical AP (Grashey view) – 40deg mediolateral beam profiling glenohumeral joint and space.
- Outlet view – Modified Y-view with beam 10deg caudad, parallel to supraspinatus. Profiles acromion under-surface for impingement.
- Westpoint axillary view – Modified axillary view (arm abducted, XRT under arm with cassette above shoulder) beam angled 25deg anterior and medial. Useful to identify anterior glenoid Bankart lesion for ?instability.
- Standard projections for the clavicle
- True AP and lateral views of the scapula
- Scapular neck
- Scapular spine
- Suprascapular notch
- Coracoid and acromion
- Bicipital groove
- Acromioclavicular joint
- Sternoclavicular joint
- Biceps tendon – Slight internal rotation, elbow 90deg, palm up.From intra-articular to myotendinous junction. Long and short. Should be enlocated within bicipital groove.
- Subscapularis – External rotation with elbow at iliac crest. Scan to insertion on lesser tuberosity. Long and short during passive external and internal rotation.
- Coracoid process – Probe on coracoid and angled up and out to acromion. Check coracoid process, coracoacromial ligament, subscapularis recess of the subacromial-subdeltoid bursa. External and internal rotation may demonstrate anteromedial impingement (distance between coracoid and lesser tuberosity in internal rotation).
- Supraspinatous – Arm posterior with palm on hip. Intra-articular biceps tendon is landmark (between supraspinatus and subscapularis), move supero-posterior to reach supraspinatus. Scan perpendicular to the tendon insertion to avoid anisotropy, include the lateral pouch of subacromial subdeltoid bursa. Long and short axis.
- Supraspinatous stress – Arm behind back with elbow at 90deg (forced internal rotation). Stretches supraspinatus and overestimates tear size.
- Dynamic assessment of subacromial impingement – Probe in coronal plane with acromion medial. Patient abducts in internal rotation, demonstrating supraspinatus and bursa passing deep to the coracoacromial arch.
- Posterior fossa – Probe posterior with increased depth, slight internal rotation, elbow 90deg, palm up. Scapular spine as landmark to distinguish supraspinous fossa (supraspinatus) from infraspinous fossa (infraspinatus, teres minor). Sweep laterally to attachments at the greater tuberosity, during external and internal rotation. Check the posterior labrum-capsular complex, posterior recess for effusion, spinoglenoid notch (medial to the labrum).
- Acromioclavicular joint – Sweep anteriorly and posteriorly to check for os acromiale.
Shoulder coil or surface coil anteriorly over shoulder.
- Oblique coronal (parallel to central slip supraspinatus tendon) T2 for rotator cuff, superior labrum – Look for SLAP, rotator cuff tear, Hill Sachs.
- Oblique sagittal (parallel to glenoid) T2 for rotator cuff – Look for denervation oedema, Hill Sachs.
- Axial T2/T2* for glenoid labrum (anterior and posterior) – Look for anteroinferior labral tear, Hills Sachs.
By convention MR en-face images (sag) display anterior to viewers left, but should report anterior as 3 o’clock (orthopaedic convention).
MRI arthrography – Injection of 1:200 dilution of gadolinium/diethylenetriamine pentaacetic acid or saline using fluoroscopic guidance. Gold standard for assessing labral abnormal. Indirect MR arthrography uses IV gadolinium followed by exercies and 15-20min delay, less reliable and doesn’t distend joint.
From direct blow or FOOSH (esp elderly patients). Proximal humerus fracture Neer classification based on displacement (”’>10mm or >45<sup>o</sup>”’) of 4 segments: articular (anatomic neck), greater and lesser tuberosities and humeral shaft (surgical neck).
- One-part fracture – <10mm or <45<sup>o</sup> displacement, held together by rotator cuff, capsule and intact periosteum.
- Two-part fracture – Only one segment displaced. Anatomic neck fracture with displacement of articular end associated with rotator cuff tear, malunion, osteonecorsis. Surgical neck fracture may be impacted, unimpacted or comminuted ± dislocation anteriorly (invariably involves greater tuberosity) or posteriorly (involves lesser tuberosity).
- Three-part fracture – 2 segments displaced with 1 tuberosity remaining in continuity with humeral head
- Four-part fracture – 3 segments displaced including both tuberosities. Usually associated with impaired blood supply to humeral head, osteonecrosis.
Fracture dislocations can occur in 2-4 part fractures, may be anterior (head splitting) or posterior (impression). Anatomic neck fracture is rare, poor prognosis with disruption of blood supply, humeral head AVN, secondary OA. Proximal humeral fracture much less common in children, most commonly buckle/torus fracture of surgical neck and proximal shaft, Salter-Harris I <5yo, II in preteens.
Surgical neck fracture may have abduction of proximal fragment by rotator cuff. Proximal 1/3 shaft fracture adduction proximal fragment by pectoralis, shortening of distal fragment by deltoid. Distal 1/3 shaft fracture abduction of proximal fragment by deltoid, shortening of distal fragment by biceps/triceps. The fracture or closed reduction may injure radial nerve coursing posterior to shaft. Tx hanging cast, internal fixation for severe/complex fracture.
Most from FOOSH, middle 1/3. SCM pulls medial fragment superiorly; weight of arm pulls lateral fragment inferiorly; pectalis and latissimus dorsi pull distal fragment medially. Most heal rapidly with minimal immobilisation and without complication. Surgical fixation only if open, high-level athletes, delayed/non-union or AC/coracoclavicular ligament disruption.
Rare in children. From direct blunt trauma. Tx of scapular body immobilisation; glenoid/neck/coracoid ORIF.
Anterior dislocation 10x more common than posterior. Transscapular/Y-view or axial view (requires abduction) for definitive diagnosis. DDx tramatic haemarthrosis (pseudodislocation), displacing humeral head inferolaterally. Vacuum phenomenon – traction force reduces joint pressure causing release of nitrogen gas in glenohumeral joint space.
Anterior dislocation – Forced external rotation, abduction and extension (eg arm tackle). On AP humeral head inferomedial to glenoid. Those <40yo associated wih antero-inferior labral tears and Hills-Sachs lesions. Those >40yo associated with supraspinatous tear, greater tuberosity fracture, subscapularis tear.
- Hill-Sachs deformity/lesion – Impaction fracture postero-latero-superior head ”’at or above level of coracoid”’. From impact on anterior inferior lip glenoid (any irregularity posteriorly is abnormal). Best seen on internal rotation views. Bone marrow oedema if <6-8 weeks old. Large lesions are associated with anterior glenohumeral instability. DDx normal posterolateral humeral head indentation below level of coracoid process.
- Bankart deformity/lesion – Tear/separation of anterior inferior labrum at anterior band of IGHL ± chip fracture with irregularity fragment. Better seen on Westpoint view.
- Glenohumeral ligament tears.
- HAGL lesion – Humeral avulsion of the IGHL
- Coracohumeral ligament tear or avulsion
- Subscapularis tear or avulsion ± subluxation of biceps tendon.
- Stripping of anterior joint capsule from glenoid (DDx normal medial attachment of the capsule which attaches at an obtuse angle cf acute angle in injury; ‘extravasation’ of injected contrast along ant-med scapular dissecting into subscapularis).
Posterior dislocation – Forceful muscle contraction (seizure, electrocution) or fall on flexed adducted arm. Usually dislocates straight posteriorly, fixed in internal rotation. AP XR may be normal, show absent crescent/half-moon overlap sign (normal overlapping of humeral head on glenoid), or lightbulb sign.
- Reverse Hill-Sachs – Trough sign on AP with depressed density deep to medial humeral head.
- Stripping of posterior joint capsule
- Reverse Bankart at posterior band of IGHL
Luxatio erecti – Inferior dislocation with fixed abduction. DDx inferior subluxation (‘pseudosubluxation’) from muscle atony (stroke, shoulder fracture).
Stability depends on static and dynamic mechanisms. Static stabilisers include labrum, capsule, glenohumeral ligaments (GHLs), negative pressure in joint space, coracohumeral arch (limiting superior subluxation). Dynamic stabilisers includes compressive forces by rotator cuff and biceps long head tendons.
- Anterior instability – Usually from previous anterior dislocation with disruption of stabilisers, esp young adults. Tx repair of damaged structures, joint capsule tightening, shortening of subscapularis.
- Posterior instability – Usually from previous posterior dislocation. Bennett lesion – rim of calcification immediately posterior to posterior glenoid rim, associated with posterior labral and rotator cuff injuries ?enthesophyte of posterior band IGHL.
- Multidirectional instability – Clinical diagnosis. Capsular laxity, dyscoordination of rotator cuff muscles. Commonly bilateral, most patients young. May have generalised joint laxity throughout the body. Tx rotator cuff strengthening exercises, surgical tightening of the capsule.
Spectrum of developmental deformity of scapular neck and glenoid. Glenoid hypoplasia (scapular neck dysplasia) is the most severe with deficient neck, wide medial glenoid; from absent glenoid neck ossification centre in childhood neuromuscular conditions (eg Erb’s palsy). Milder form is deficinecy of posterior glenoid with medial sloping, may be associated with posterior instability, posterior labral tears.
- Sternoclavicular hyperostosis
- Degenerative arthritis common, usually incidental.
- Dislocation with large forces (stronge joint) in any direction. Posterior dislocation may compress great vessels or trachea. DDx SH I/II (medial epiphysis doesn’t ossify until 18-20yo, fuses 25yo).
- Infection usually IVDU or elderly.
Osteophytes may narrow subacromial space causing rotator cuff impingement.
Injury disrupts AC ligaments before stronger coracoclavicular ligaments. Passive traction with ~7.5kg weight in hand may reveal/upgrade injury. AC injury grading:
- Grade 1 – Sprain without gross disruption. Tender, XR normal or mild joint laxity with minimal subluxation/widening.
- Grade 2 – AC ligament rupture, intact coracoclavicular ligament. Discointinuous/widened AC joint >5mm or >2-3mm/50% diff to contralateral side (DDx distal clavicle erosion, cleidocranial dysplasia with clavicular hypoplasia). Normal coracoclavicular distance.
- Grade 3 – AC and coracoclavicular ligament rupture. Coracoclavicular distance >12mm or >5mm/50% diff to contralateral side.
- Grade 4 – Posterior dislocation of clavicle relative to acromium, or into/through trapezius (less commonly inferior dislocation below coracoid). May compress supraspinatus against scapula. Requires axillary view or CT. Tx surgical fixation.
(Hydroxyapatite deposition disease, HADD). Small asymptomatic deposits of calcium hydroxyapatite in injured parts of tendons (silent phase) -> enlargement causing impingement (mechanical phase). May rupture into joint space, bursa (calcific bursitis, may -> fibrosis), greater tuberosity or periarticular tissues. Tx surgical enucleation or percutaneous aspiration/fenestration and lidocaine/corticosteroid lavage.
Rotator Cuff Impingement
Compression of rotator cuff, subacromial bursa and biceps tendon between coracoacromial arch and humeral head. Most have rotator cuff pain, reproducible with overhead movement (deltoid initiates shoulder abduction). Most tears are due to chronic impingement.
- Subacromion impingement (most) – Supraspinatus between anterior acromion and greater tuberosity or undersurface AC joint from abduction of humerus. Usually has at risk factors including: Bigliani type 2/3 coracoacromial arch, anterior/lateral spurs, AC joint osteophytes, capsule hypertrophy, os acromiale, deformed humeral head from fracture, glenohumeral instability. Anterior acromial/traction spur is an enthesophyte of the coracoacromial ligament extending antero-infero-medially. Chronic/repetitive impingement can cause anterior acromial/superior greater tuberosity irregularity and cystic change (seen in impingement and tear). The undersurface humeral acromion may have sclerosis or remodelling with concavity matching the humeral head. May cause or be caused by subacromial bursitis. Progresses to rotator cuff tear. Tx arthroscopic subacromial decompression with anterior acromioplasty and coracoacromial release.
- Coracoid impingement – Supscapularis
- Internal impingement – Posterosuperior glenoid impingement esp throwing athletes with elbow posteriorly causing supra/infra-spinatus tendons to impinge on glenoid rim. May cause injury to superior labrum, rotator cuff, IGHL, greater tuberosity or glenoid. In sketelally immature may cause irregularity and sclerosis of posterior physis.
The acromion angles anterosuperiorly from the scapular spine. Bigliani types of acromion arch: type 1 flat; type 2 concave anteriorly (no focal subacromial space narrowing); type 3 antero-inferior hook (acute narrowing of space); type 4 convex superiorly. Type 2-3 are assocociated with supraspinatus impingement.
Rotator Cuff Tendinopathy and Tears
Rotator cuff comprises tendons of subscapularis, supraspinatus, infraspinatus, teres minor. From chronic impingement (most), cuff degenertaion (aging, reduced vascularity), RA pannus or acute injury.
Supraspinatus injury most common, ”’critical zone 10mm proximal to insertion”’ (watershed between humeral and muscular blood supply). Most tears begin at bone/tendon interface just lateral to the bicipital groove. Subscapularis tears allows dislocation of biceps tendon (attaches to lesser tubercle with some fibres crossing the intertubercular groove to greater tuberosity forming the transverse humeral ligament). Normal tendon signal is low T1 and T2, but may have intermediate/high signal. Thinning of the tendon and high T1 signal (that doesn’t increase with T2) may be normal in partial voluming of peritendinous fat, plane of imaging slightly off the tendon (muscle slip partial voluming), ‘magic angle’ effect (apparent high signal in tendon lying 55deg to bore of magnet eg critical zone, not seen on T2 or long TE), tendinopathy.
- Tendinopathy – Myxoid and fibrillar degeneration of tendon, asymptomatic, no inflammatory cells on histology. High critical zone T1 not increasing with T2. May be treated with resection (?progresses to tear).
- Tendonitis/tendinosis – Oedema with high signal on T1 increasing with T2. Tendon fibres intact.
- Partial tear – Irregularity or thinning. Bursal, articular/humeral surface or instrasubstance tear (interstitial delamination). High signal on T1, increasing with T2, typically more than with tendinosis. Will not heal spontaneously if >25% of cuff thickness. ‘Rim rent’ or ‘foot-print’ tear – articular-sided tear at fibre insertion, commonly anteriorly (hence may be overlooked if internally rotated)
- Full thickness tear (perforation) – Associated with bursal effusion and allows enhancement on arthrography. Geyser sign – leakage of contrast into subdeltoid/subacromial bursa (doesn’t normally connect with joint same as subcoracoid bursa), outlining AC joint.
- Complete tear – Full thickness and full width tendon disruption, must be associated with tendon retraction. If chronic then muscle atrophy with unlikely benefit from surgery. Retraction >30-40mm has poorer surgical results.
- Massive rotator cuff tear – More than one tendon involved, usually supraspinatus extending posterior to infraspinatus and anterior through rotator interval to subscapularis. Chronic massive tear causes high-riding humeral head, subacromial space <6mm
DDx suprascapular nerve entrapment or neuritis, nondisplaced greater tuberosity avulsion fracture, bursitis.
Long Head of Biceps Tendinopathy and Tears
Passes in bicipital groove to supraglenoid tubercle and/or superior glenoid labrum at 1 o’clock (biceps labral complex). Can be impinged by abnormal acromion (similar to supraspinatus tendon) -> tenosynovitis or tendonitis. Tenosynovitis – fluid in tendon sheath surrounding otherwise normal tendon. Enlargement or signal within the tendon indicates tendonitis or partial tear. Tendon disruption/dislocation if tendon not seen on one or more axial images. Dislocation is uncommon, tendon may lie anteromedial to the joint, must have associated subscapularis tear.
Glenohumeral Capsule and Labrum
Glenoid labral tear or detatchment causes glenohumeral joint instability. May be caused by dislocation, repeated trauma (throwing). The normal labrum is triangular, anterior > post. Tears in anterior labrum > posterior > superior. Do not call tears in the anterosuperior labrum (12-3 o’clock), at or above the level or the subscapularis tendon; multiple variants here and is rarely torn/detatched. Tear or detached labrum – joint fluid/enhancement between bony glenoid and base of labrum, or labral truncation, may be associated with paralabral cyst. Linear/amorphous signal in normal low signal labrum (DDx magic angle effect with short TE sequences). Best seen on CT/MR arthography. Anterior labral tears best seen on ABER position (abduction and external rotation with hand behind head), pushing humerus against the labrum ‘prying’ tears open.
- SLAP (superior labral anterior to posterior) – Biceps labral complex injury, variably involving the superior labrum, proximal biceps tendon and biceps attachment. From forced extension, rapid abduction in fall, deceleration phase of throwing, pulling of long head of biceps or older patients with cuff tears. Uncommon dislocation with only 20% associated with instability. Usually orientated antero-supero-lateral (ASL, 1st 3 letters of SLAP) to postero-infero-medial cf sublabral recess which points towards the acromion and shouldn’t extend posterior to biceps tendon anchor at ~11 o’clock, is smooth <2-3mm thick. Best seen in external rotation, caudal retraction placing strain on biceps tendon/labrum. 14 subtypes, need to state whether it extends into the biceps tendon.
- Anteroinferior labral tear – From anterior dislocation. May be associated with Hills Sachs lesion. ‘If unsure, call it a Bankart’.
- Bankart lesion – Displaced labrum with periosteum torn.
- Perthes lesion – Labrum remaining attached to periosteum, periosteum not torn.
- GLAD lesion (glenolabral articular disruption) – Nondisplaced avulsion of the anteroinferior labrum and fragment of adjacent glenoid cartilage.
- ALPSA lesion (anterior labral periosteal sleeve avulsion) – Avulsion of anteroinferior labrum and anterior band IGHL. Periosteium not torn. Highly associated with anterior instability.
- HAGL (humeral avulsion glenohuneral ligament) – Injury at the humeral attachment of the IGHL.
Inflammation causing tight joint capsule with low capacity causing pain, restricted ROM. DDx surgical tightening.
Suprascapular Nerve Entrapment
The suprascapular nerve (branches of C4-6 roots of brachial plexus) passes superior to the scapula (anterior to posterior); medial to coracoid, posterior in the suprascapular notch (above the spine) giving branches to supraspinatus; spinoglenoid notch (inferior to spine) in posterior scapular then innervates infraspinatous. Nerve injury from traction, neuritis or compression. Spinoglenoid/suprascapular entrapment by mass, displaced fracture, ganglion/synovial/paralabral cyst (frequently from labral tear with one-way valve) esp weightlifters. Suprascapular entrapment affects supraspinatous and infraspinatous; spinoglenoid only the infraspinatous. Acute denervation 2-4/52 causes diffuse oedema; chronic irreversible fatty infiltration and atrophy.
Post-op changes & complications in humeral head prosthesis
Surgery may disrupt normal tissue planes. MR artifact from suture anchors, hardware, micrometal debris; minimised with FSE without chemical FS.
- Suture anchors may displace, may incite a granulomatous reaction withsurrounding fluid.
- Tendon repairs are not water-tight hence contrast leaks across. Must see an actual defect/tract to diagnose a new tear.
Quadrilateral Space Syndrome
Quadrilateral space is limited by the teres minor superiorly, teres major inferiorly, long head of triceps medially, diaphysis of humerus laterally. Syndrome from fibrous bands (most, difficult to see on imaging), scarring, mass lesions or fracture fragments in quadrilateral space; impinging on the axillary nerve. Symptoms are similar to rotator cuff tear. Causes denervation of posterior deltoid and teres minor (deltoid muscle rarely involved). Tx physical therapy to break up bands.
(Brachial neuritis). Sudden onset severe pain followed by profound weakness in 1-2/7 without history of trauma. Unknown aetiology but associated with vaccination, viral illness or GA in 1/3, bilateral in 10-15%. Self-limiting. Neurogenic oedema in muscle groups of suprascapular nerve (spuraspinatus/infraspinatus) and/or axillary nerve (teres minor/deltoid). DDx traumatic traction nerve injury (identical appearance and more common).