MRI Anatomy of the Shoulder

Functional Anatomy Glenohumeral joint is a ball and socket synovial. Glenoid cavity inherently unstable. Stability provided by: Static constraints 3 glenohumeral ligaments glenoid labrum joint capsule Dynamic constraints, - rotator cuff muscles counteract the action of the deltoid by preventing the head of the humerus from moving superiorly when the arm is raised An imbalance between the deltoid and the rotator cuff muscle strength may result in excessive superior movement of the humeral head, causing impingement of subacromial structures.

The glenohumeral joint has the following supporting structures: Superiorly Coraco-acromial arch Long head of the biceps tendon Tendon of supraspinatus muscle Anteriorly Anterior labrum 3 Glenohumeral ligaments SGHL, MGHL, IGHL (anterior band) Subscapularis tendon Posteriorly Posterior labrum Posterior band of the IGHL Infraspinatus tendon Teres minor tendon Lateral view Coracoacromial arch contains: 1. Coracoacromial ligament 2. Acromion process 3. Coracoid process

Articular surfaces The shoulder joint is composed of 3 bones and five articulations. Bones: Scapula Humerus Clavicle Articulations: Glenohumeral joint Acromio-clavicular joint Scapulothoracic joint Sternoclavicular joint Coracoclavicular joint

Joint capsule Attached proximally to the glenoid labrum Attached distally to the anatomical neck of the humerus Capsule is thickened anteriorly by glenohumeral ligaments Herniation of synovial membrane through an anterior defect in capsule & glenohumeral ligaments forms the subscapular bursa

Bursae Subdeltoid Subcoracoid Coracobrachial Subacromial Between joint capsule and deltoid muscle Subcoracoid coracoid process Coracobrachial Between subscapularis and coracobrachialis Subacromial acromion Subscapular bursa subscapularis tendon

Rotator Interval Triangular space between the supraspinatus and subscapularis tendons Contains long head of biceps and SGHL Acts to prevent anterior dislocation of the shoulder Picture: rotator cuff interval in sagittal plane, with superior capsular complex (in green), subscapularis tendon (SSC), superior glenohumeral ligament (SGHL), and long portion of biceps tendon (LPB) and passing beneath deep fibers of supraspinatus (SSP).

Ligaments 3 glenohumeral ligaments Coracohumeral ligament Superior Middle Inferior Coracohumeral ligament Transverse humeral ligament Between greater and lesser tuberosities of humerus, maintains long head of biceps in bicipital groove

Superior glenohumeral ligament Coracohumeral ligament Long head biceps tendon A fat suppressed axial T1-weighted MR arthrogram image demonstrates the superior glenohumeral ligament (arrow), the glenoid labrum (arrowhead), the long head biceps tendon (short arrow), and the coracohumeral ligament (curved arrow Superior glenohumeral ligament two sites of origin supraglenoid tubercle just anterior to long head of biceps origin on superior labrum + the base of coracoid - inserts superior to lesser tuberosity

SGHL Sagittal 2 Origins: just anterior to long head of biceps AND base of coracoid Insertion: lesser tuberosity of humeral head

SGHL Axial

Middle glenohumeral ligamant fat suppressed oblique sagittal T1-weighted MR arthrogram image demonstrating the middle glenohumeral ligament (arrow) Arises from the anatomic neck and inserts into the mid-anterior labrum Middle part of the ligament is seen just posterior to subscapularis Shows maximum variation in size and shape among all three glenohumeral ligaments

MGHL Sagittal Originate on the anatomic neck Inserts in mid anterior labrum

MGHL Axial

Inferior glenohumeral ligament A fat suppressed oblique sagittal T1-weighted MR arthrogram image, demonstrating the anterior and posterior bands of the inferior glenohumeral ligament (arrows) Most important glenohumeral ligament, Main static stabilizer of the shoulder in the abducted or functional position Attaches to inferior glenoid labrum Has two band like thickenings, anterior and one posterior Has a lax part, axillary pouch, in between Axillary recess Subacromial-subdeltoid bursa

Glenoid labrum The glenoid labrum is a fibrocartilaginous structure that attaches to the glenoid rim and is about 4 mm wide. increases the superior-inferior diameter of the glenoid by 75% and the anterior-posterior diameter by 50% Anteriorly, the glenoid labrum blends with the anterior band of the inferior glenohumeral ligament. Superiorly, it blends with the biceps tendon and the superior glenohumeral ligament. It is usually rounded or triangular on cross-sectional images.

Labral anatomy: Axial The normal labrum demonstrates low signal intensity on all pulse sequences, due to the lack of mobile protons in this dense fibrocartilage. On cross sectional imaging, the normal labrum is most commonly triangular, but can also be round, cleaved, notched, flat, or absent.

Labral Anatomy: Coronal A fat suppressed oblique coronal T2-weighted MR image demonstrates homogeneously low signal intensity in the normal superior labrum.

Labral variants These normal variants are all located in the 11-3 o'clock position. There are many labral variants

It is important to recognise these variants, because they can mimick a SLAP tear. These normal variants will usually not mimick a Bankart-lesion, since these are located at the 3-6 o'clock position, where these normal variants do not occur. Labral tears can occur at 3-6 o’clock

Sublabral recess Synovial recess between the superior labrum and the glenoid rim created by the attachment of the biceps tendon on the supraglenoid tubercle. Because of this recess, the labrum does not attach to the glenoid rim at the 12 o'clock position. There are 3 types of attachments of the superior labrum:
Type I No recess between glenoid cartilage and labrum
Type II Small recess.
Type III Large sublabral recess. 
 This sublabral recess can be difficult to distinguish from a SLAP-tear or a sublabral foramen.

Sublabral Foramen An unattached anterosuperior labrum at the 1-3 o'clock position. Anterior to biceps tendon 
It is seen in 11% of individuals. 
Not to be confused with a sublabral recess or SLAP-tear, which are also located in this region. 
 Sublabral recess located at 12 o’clock where biceos tendon inserts, does not extend to the 1-3 o’clock position SLAP tears can extend to the 1-3 o’clock poisition but the attachment of the biceps tendon to the superior labrum should be involved

Differences between an sublabral recess and a SLAP-tear: 
A recess more than 3-5 mm is always abnormal and should be regarded as a SLAP-tear. Shows how difficult it can be to tell the difference

Buford complex Congenital labral variant 2 Features:
Anterosuperior labrum is absent in the 1-3 o'clock position Middle glenohumeral ligament is usually thickened. 
It is present in approximately 1.5% of individuals. Images show the absent anterosuperior labrum and thickened middle ghl

Os Acromiale On MR an os acromiale is best seen on superior axial images. Results from failure of one of the acromial ossification centers to fuse. 
5% of the population. 
Usually an incidental finding, regarded as a normal variant. 
May cause impingement because if it is unstable, it may be pulled inferiorly during abduction by the deltoid, which attaches here.

Acromion: 3 types Type 1 is a flat undersurface with a high angle of inclination. Type 2 is a curved arc and decreased angle of inclination. Type 3 is hooked anteriorly with a decreased angle of inclination.

Axial Anatomy

The axillary artery begins at the lateral border of the first rib as a continuation of the subclavian artery. It changes its name to brachial artery at lower inferior border of the teres major muscle (8). MRI of the shoulder. Axial T1-weighted view. Image 1 1, Axillary vein and artery. 2, Clavicle. 3, Acromioclavicular joint. 4, Acromion. 5, Supraspinatus muscle

Axial Deltoid Anterior clavicular fibres – arise from superior anterior aspect of lateral clavicle Lateral acromial fibres – arise from superior aspect of acromion process Posterior fibres – arise from posterior border of spine of scapula 1, Axillary vein and artery. 2, Deltoid muscle. 3, Coracoid process. 4, Supraspinatus muscle. 5, Acromion

Axial Supraspinatus muscle Relatively small muscle Runs from the supraspinatous fossa of scapula to the greater tubercle of the humerus 1, Pectoralis major muscle. 2, Axillary vein and artery. 3, Coracoid process. 4, Deltoid muscle. 5, Supraspinatus muscle. 6, Acromion. 7, Scapula. 8, Subscapularis muscle

Axis of supraspinatous tendon The supraspinatus tendon is the most important structure of the rotator cuff and subject to tendinopathy and tears. 
Tears of the supraspinatus tendon are best seen on coronal oblique and ABER-series. 
In many cases the axis of the supraspinatus tendon (arrowheads) is rotated more anteriorly compared to the axis of the muscle (yellow arrow). 
When you plan the coronal oblique series, it is best to focus on the axis of the supraspinatus tendon.

Sagittal Supraspinatus Infraspinatus Teres minor The attachments of the 3 rotator cuff muscles that insert onto the greater tubercle of the humerus can be abbreviated SIT when viewed from superior to inferior: Supraspinatus Infraspinatus Teres minor Sagittal post post 2, Subscapularis tendon. 3, Biceps tendon (long head). 4, Supraspinatus muscle. 5, Acromion. 6, Infraspinatus muscle. 7, Deltoid muscle. 8, Teres minor muscle. Greater tubercle - anterolateral SITS inlcudes Subscapularis which inserts onto the lesser tubercle of the humerus

Axial Pec major Deltoid anterior Pec minor Now going to look at infraspinatus and subscapularis1, Pectoralis major muscle. 2, Deltoid muscle (anterior). 3, Coracoid process. 4, Humeral head. 5, Glenoid. 6, Supraspinatus muscle. 7, Scapula. 8, Deltoid muscle. 9, Infraspinatus muscle. 10, Subscapularis muscle. 11, Axillary vein and artery. 12, Pectoralis minor muscle. Supraspinatus inserts most superiorly to greater tuberosity humeral head Subscapularis Infraspinatus Deltoid posterior

Infraspinatus (SIT) Thick triangular muscle which occupies most of the infraspinatous fossa Attaches medially to the infraspinatus fossa and laterally to the middle facet of the greater tubercle of the humerus Trapezoidal insertion of infraspinatus onto humerus is much larger than the insertion of the supraspinatus Coronal views of the 3 facets of the greater tubercle of the humerus

*Tip* Coronal oblique MRI Supraspinatus – fibres run horizontally Infraspinatus – fibres have a slightly oblique orientation 7 – supraspinatus 2 - infraspinatus

Subscapularis Subscapular fossa = anterior Large triangular muscle which fills the subscapular fossa Inserts onto the lesser tubercle of the humerus Subscapular fossa = anterior Infraspinatous fossa = posterior ant post

Axial Coracobrachialis Deltoid as one Coracobrachialis is the smallest of the three muscles that attach to the coracoid process. The other 2 muscles are pectoralis minor and biceps brachii. Distal insertion upper medial aspect of arm Teres minor 1, Pectoralis major muscle. 2, Biceps tendon (long head). 3, Deltoid muscle (anterior). 4, Humeral head. 5, Glenoid. 6, Teres minor muscle. 7, Deltoid muscle. 8, Infraspinatus muscle. 9, Subscapularis muscle. 10, Coracobrachialis muscle. 11, Pectoralis minor muscle. Teres minor most inferior of the SIT muscles

Teres minor (SIT) Origin: Superior part of lateral border of scapula Insertion: Inferior facet of greater tuberosity of humerus Coronal view: 2 – infraspinatus, 4 – teres minor

Axial The short head of the biceps originates from the coracoid process (2) 1, Pectoralis major muscle. 2, Biceps tendon (short head). 3, Biceps tendon (long head). 4, Deltoid muscle (anterior). 5, Humeral head. 6, Glenoid. 7, Teres minor muscle. 8, Deltoid muscle. 9, Infraspinatus muscle. 10, Subscapularis muscle. 11, Coracobrachialis muscle. 12, Pectoralis minor muscle. The long head originates from the supraglenoid tubercle (3)

Tendon of long head passes down along the intertubercular/bicipital groove of the humerus into the joint capsule Both heads arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. Long head forms biceps-labral complex with superior glenohumeral ligament Biceps labral complex: 1. long head biceps 2. superior labrum 3. SGHL When the humerus is in motion, the tendon of the long head is held firmly in place in the bicipital groove by the greater and lesser tubercles and the overlying transverse humeral ligament.

Coronal Long head

Coronal anatomy

Coronal Trapezius Posterior humeral circumflex artery and axillary nerve 1, Trapezius muscle. 2, Acromion. 3, Deltoid muscle. 4, Humeral head. 5, Infraspinatus muscle. 6, Teres minor muscle. 7, Teres major muscle. 8, Tricipital muscle. Arrow, Posterior humeral circumflex artery and axillary nerve. Going to look at teres major extends longitudinally from the occipital bone to the lower thoracic vertebrae and laterally to spine of the scapula Teres major Triceps

Teres major It arises from the dorsal surface of the inferior angle of the scapula Inserts onto intertubercular sulcus of humerus 1, Trapezius muscle. 2, Acromioclavicular joint. 3, Acromion. 4, Deltoid muscle. 5, Humeral head. 6, Supraspinatus muscle. 7, Spine of the scapula. 8, Infraspinatus muscle. 9, Scapula. 10, Subscapularis muscle. 11, Teres major muscle. (Teres minor)

Coronal Infraspinatus Teres minor Triceps Teres major Nice picture of the insertions of infraspinatus (3) and teres minor (7) onto the greater tubercle of the humerus Teres major

Coronal Supraspinatus Subscapularis Teres major Been over these muscles 1, Trapezius muscle. 2, Clavicle. 3, Acromioclavicular joint. 4, Acromion. 5, Deltoid muscle. 6, Greater tuberosity. 7, Humeral head. 8, Supraspinatus muscle. 9, Glenoid. 10, Subscapularis muscle. 11, Teres major muscle. Subscapularis Teres major

Sagittal Anatomy

Sagittal P A 2 patterns on sagittal: SIT (posterior tendon insertions) CCA (bonesof AC joint from ant to post) 1, Coracobrachialis. 2, Subscapularis tendon. 3, Humeral head. 4, Coracoid process. 5, Deltoid muscle. 6, Biceps tendon (long head). 7, Clavicle. 8, Acromioclavicular joint. 9, Supraspinatus muscle. 10, Acromion. 11, Infraspinatus muscle. 12, Deltoid muscle. 13, Teres minor muscle.

Acromioclavicular joint Axial: Clavicle medial Acromion lateral Sagittal: Acromion posterior Coracoid anterior The undersurface of the acromion should align with the undersurface of the clavicle Cl Ac Ant Co Post

Sagittal: SIT SIT 4, 6 8 2, Subscapularis tendon. 3, Biceps tendon (long head). 4, Supraspinatus muscle. 5, Acromion. 6, Infraspinatus muscle. 7, Deltoid muscle. 8, Teres minor muscle.

MR shoulder arthrogram Technique whereby injection of contrast media into the joint allows for evaluation of capsule and internal joint structures. Originally performed using plain radiography. Now injection of gadolinium allows MR arthrography. CT arthrograms can also be performed.

Advantages Joint distension, outlining intra-articular structures Improved detection of tears, including articular surface partial tears Demonstration of communication between joint and extra-articular abnormalities eg. Paralabral cysts and bursae.

Disadvantages and pitfalls Risks assoc with needle placement into joint: infection, haemorrhage, synovial reaction. Avoid oblique position – glenoid in profile – aiming for joint space places the labrum at risk Correct needle positioning is essential Extra articular contrast can complicate findings on MR and simulate tears

Technique Fluoroscopically guided anterior approach is most widely performed. Perform routine preparation Correct patient Correct side No iodine allergies Explain procedure to patient, obtain consent Confirm indication

Indications Assessment of integrity of rotator cuff Evaluation of shoulder instability Diagnosis of labral pathology Diagnosis of adhesive capsulitis

Technique Sterile procedure Fluoroscopically guided Obtain control images of shoulder Patient supine, AP view Arm in external and internal rotation Angle tube to view acromion in profile – clear visualisation of sub-acromial space Evaluate for calcium deposition in tendons

Patient Positioning Supine position creates oblique orientation of glenoid surface. Posterior glenoid overlaps humeral head on AP Anterior glenoid lies medial to humeral head Thus needle directed AP at humeral head will not injure anterior labrum External rotation exposes a larger articular surface anteriorly Placing a sandbag in the patient’s hand may help maintain the position Arthrogram – axial MRI. contrast material distending the glenohumeral joint and long head of the biceps brachii tendon sheath (arrowhead). Note the oblique orientation of the glenoid articular surface (curved arrow) and medial location of the anterior labrum (straight arrow) relative to the humerus.

Technique Determine skin entry site using fluoroscopy Just lateral to the medial cortex of the humeral head (never medial) At junction of middle and lower third of humeral head Ideally central in fluoroscopic image Locally anaesthetise skin and subcutaneous tissue AP fluoroscopic image demonstrates a spinal needle (arrow) centered over the needle hub, just lateral to the medial cortex of the humeral head. Note the sclerotic line, which approximates the lateral border of the glenohumeral joint (arrowheads) – anatomic neck.

Technique Prepare contrast whilst allowing local anaesthetic to take effect (can also be done before procedure starts) Bloem protocol: 20 ml syringe 10 ml sterile water 5 ml iodine based non-ionic LOCM (eg.Ultravist, Omnipaque) 5 ml lignocaine 0.1 ml gadolinium Other: Test injection with 1-2 ml of lignocaine Contrast: 10 ml saline, 10 ml Iodine LOCM, 0.1 ml gadolinium, 0.3 ml 1:1000 adrenaline Syringe connected to connecting catheter(line)

Technique Advance needle (usually 20G spinal needle with stylet) in direct AP direction posteriorly. Continue until contact with humeral head. Consider test injection with lignocaine. Should only meet low resistance when in joint space If high resistance – possibly in hyaline cartilige – carefully manipulate needle by rotation and minimal retraction (few mm) Loss of resistance indicates either intra-articular or bursal location Don’t use gadolimium for test injection to avoid inadvertant injection of Gad outside the joint leading to misinterpretation as rotator cuff/capsular injury

Technique Inject iodinated contrast to distinguish between intra-articular and bursal location Intra-articular contrast will collect in glenohumeral joint space If intra-articular position is confirmed, continue with proper contrast injection Usually inject 14 – 16 ml of contrast, depending on patient and pathology. A patient with chronic shoulder subluxation may require more volume, whereas a patient with adhesive capsulitis requires less. has been shown that exercise after shoulder arthrography has no beneficial or detrimental effect on MR image quality or on the depiction of rotator cuff or labral tears

Alternative: Posterior approach Can also do ultrasound guided appraoch When suspecting anterior pathology. Avoids the interpretative difficulties that may be associated with anterior extracapsular contrast extravasation Aim for the inferomedial quadrant of humeral head within boundary of anatomic neck (interrupted line).

Other techniques Inject only water, no gadolinium Indirect arthrogram Achieves effect of distension Need to use T2 sequences Disadvantage: Difficult to distinguish between small full thickness and partial tears Indirect arthrogram 1 mmol/kg Gd IV Exercise joint for 5 to 5 minutes Gd passes into joint space Can perform T1 images Disadvantages: Joint not distended Extra-articular structures will also enhance

MR technique Three plane T1 with fat sat T2 with fat sat axial and coronal oblique (Consider Ax GRE to evaluate for calcification) Sagittal oblique T1/PD without fat suppression Some protocols suggest pre contrast T2 sequences. Detection of intra-substance and bursal surface tears. Pre-existing fluid collections and cysts Coronal oblique parallel to supraspinatus tendon (not muscle) Sagittal oblique perpendicular to glenoid surface (ABER – Abduction and External rotation sometimes used for evaluation of anterior and inferior GHL’s)

ABER view Labral tears
The abduction external rotation (ABER) view is excellent for assessing the anteroinferior labrum at the 3-6 o'clock position, where most labral tears are located. 
Inferior glenohumeral ligament stretched resulting in tension on the anteroinferior labrum, allowing intra-articular contrast to get between the labral tear and the glenoid. Rotator cuff tears
Very useful for both partial- and full-thickness tears of the rotator cuff. 
Releases tension on the cuff relative to the normal coronal view obtained with the arm in adduction. 
 Images in the ABER position are obtained in an axial way 45º off the coronal plane (figure). Notice red arrow indicating a small Perthes-lesion, which was not seen on the standard axial views.

Rotator cuff tears Arthrography improves detection of tears as the joint is being distended and contrast forced into small defects. T1 (quicker) sequences with improved SNR can be used Diagnoses full thickness tears and articular surface partial thickness tear Not of value in intra-substance or bursal surface partial thickness tears

Full-thickness tear will demonstrate the gadolinium contrast solution extending first through a defect in the cuff and then into the subacromial-subdeltoid bursa. Articular-surface partial-thickness tears show a focal extension of the contrast solution into the substance of the tendon. Fat suppression is necessary as peribursal fat may mimic contrast.

References Ryan S, McNicholas M, Eustace S. Anatomy for diagnostic imaging. CT and MR Arthrography of the Normal and Pathologic Anterosuperior Labrum and Labral-Bicipital Complex. October 2000 RadioGraphics, 20, S67-S81. www.radiologyassistant.nl Radiology Assistant: MR Shoulder Part I. http://musculoskeletal-radiology.blogspot.com/2006/09/glenohumoral-ligaments.html Jacobson et al. Aids to Successful Shoulder Arthrography Performed with a Fluoroscopically Guided Anterior Approach. Radiographics. 2003; 23:373–379 Beltran et al. MR Arthrography of the Shoulder: Variants and Pitfalls. Radiographics. 1997; 17:1403-14 12