Shoulder

IMAGING ANATOMY

Overview

• Rotator cuff

Consists of supraspinatus, infraspinatus, teres minor, subscapularis muscles, and tendons

Cuff tendons blend with shoulder joint capsule

Supraspinatus and infraspinatus tendons are inseparable at insertion

Anterior 2.25 cm of tendon comprises supraspinatus tendon insertional area
• Supraspinatus muscle

Origin: Supraspinatus fossa of scapula

Insertion: Superior facet (horizontal orientation) and anterior portion of middle facet of greater tuberosity

– Broad insertional area

Nerve supply: Suprascapular nerve

Blood supply: Suprascapular artery and circumflex scapular branches of subscapular artery

Action: Abduction of humerus

Muscle consists of 2 distinct portions

– Anterior portion is larger, fusiform in shape, has dominant tendon, and is more likely to tear

– Posterior portion is flat and has terminal tendon

Most commonly injured rotator cuff tendon
• Infraspinatus muscle

Origin: Infraspinatus fossa of scapula

Insertion: Mid to posterior aspects of middle facet of greater tuberosity; centrally positioned within tendon

Nerve supply: Suprascapular nerve, distal fibers

Blood supply: Suprascapular artery and circumflex scapular branches of subscapular artery

Action: External rotation of humerus and resists posterior subluxation
• Teres minor muscle

Origin: Lateral scapular border, middle 1/2

Insertion: Inferior facet (vertical orientation) of greater tuberosity

Nerve supply: Axillary nerve

Blood supply: Posterior circumflex humeral artery and circumflex scapular branches of subscapular artery

Action: External rotation of humerus

Least commonly injured rotator cuff tendon
• Subscapularis muscle

Origin: Subscapular fossa of scapula

Insertion: Lesser tuberosity and up to 40% of tendon may insert along adjacent part of surgical neck

Some fibers cross over to lateral lip of bicipital groove, reinforcing and blending with transverse ligament

Nerve supply: Subscapular nerve, upper and lower

Blood supply: Subscapularis artery

Action: Internal rotation of humerus, also adduction, extension, depression, and flexion

4-6 tendon slips converge into main tendon; multipennate morphology increases strength
• Rotator cuff tendon blood supply

Derived from adjacent muscle, bone, and bursae

Normal hypovascular regions in tendons

– Termed critical zone: ~ 1 cm proximal to insertion

– Vulnerable to degeneration and calcific deposition

– However, insertional area is more prone to tearing than critical zone
• Biceps tendon, long head

Origin: Superior glenoid labrum (biceps anchor)

– Portions may attach to supraglenoid tubercle, anterosuperior labrum, posterosuperior labrum, and coracoid base

Runs along superior aspect of shoulder to bicipital groove

Action: Stabilizes and depresses humeral head

Anatomic variants: Anomalous intra- and extraarticular origins from rotator cuff and joint capsule

Tendon sheath communicates with glenohumeral joint and normally contains small amount of fluid
• Subacromial-subdeltoid fat plane

Subacromial and subdeltoid portions

– ± subcoracoid extension in some patients

Fat plane is superficial to bursa

May be interrupted or absent in normal patients

Attached along free border of coracoacromial ligament and deep surface of deltoid muscle, and humeral neck
• Rotator cuff interval

Space between supraspinatus and subscapularis tendon through which biceps tendon passes

Borders of rotator cuff interval

– Triangular-shaped space

– Reflections of glenohumeral ligament and coracohumeral ligament form biceps reflection pulley

– Biceps reflection pulley stabilizes biceps tendon within rotator cuff interval

– Superior border: Leading edge of supraspinatus

– Inferior border: Superior aspect of subscapularis tendon

– Lateral border: Long head of biceps tendon and bicipital groove

– Medial border: Base of coracoid process

Contents of rotator interval

– Long head of biceps tendon; biceps reflection pulley
• Coracoacromial ligament

Forms coracoacromial arch along with acromion and coracoid process

– Reinforces inferior aspect of acromioclavicular joint

Extends from distal coracoid to subacromial area

Broad insertion to undersurface acromion

– Ligament is thicker at acromion (normal thickness < 2.5 mm) and may be associated with spurs
• Glenoid labrum

Triangular-shaped rim of fibrocartilage, which extends around periphery of glenoid

ANATOMY IMAGING ISSUES

Imaging Approaches

• Tendons best seen when on stretch

High-resolution linear transducer

Long-axis (longitudinal) & transverse view of each tendon

Each part of tendon needs to be examined; anisotropy prevents all parts of curved rotator cuff tendons from being seen at same time

Need to realign (“toggle”) probe to see different parts of tendons
• Supraspinatus tendon

Arm extended and internally rotated behind lumbar region (Crass position)

– If too painful, hand in behind hip (“back pocket”) with elbow close to body (modified Crass position)
• Infraspinatus and teres minor tendons

Arm flexed and internally rotated with hand placed on contralateral shoulder

Teres minor tendon located posteroinferior to infraspinatus tendon
• Subscapularis tendon: Arm neutral and externally rotated
• Long head of biceps tendon

Arm neutral and externally rotated

Vary degree of external rotation for optimal view of biceps tendon

Check for tendon subluxation
• Subacromial-subdeltoid bursa

Stretching tendons may squeeze fluid from area of bursa under inspection

Examine in all positions and also in neutral position

Fluid collects preferentially just lateral to acromion and proximal humerus and near coracoacromial ligament

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Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

IMAGING ANATOMY

Overview

ANATOMY IMAGING ISSUES

Imaging Approaches

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Shoulder

Shoulder

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Radiology Key

Fastest Radiology Insight Engine

Shoulder

Shoulder

IMAGING ANATOMY

Overview

ANATOMY IMAGING ISSUES

Imaging Approaches

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