Scapula !

The scapula, or shoulder blade, is the flat bone on the upper back; it forms the shoulder socket and anchors the rotator cuff.

See in 3D →

Opens in the Durgical app, no sign-up needed.

What it is

The flat triangular shoulder blade on the back of the ribs, with the acromion, coracoid and glenoid socket.

What it does

Gives the arm its socket and anchors the rotator cuff; it glides on the ribs as the arm rises.

Key facts

Joints with: Glenohumeral joint (humeral head); acromioclavicular joint (clavicle); scapulothoracic gliding plane on ribs 2–7
Landmarks: Spine, acromion, coracoid process, glenoid cavity; supra- and infraspinous fossae; superior angle T2, inferior angle T7; subscapular fossa; suprascapular notch; supraglenoid tubercle (long head of biceps) and infraglenoid tubercle (long head of triceps)

Relations

In front: Subscapularis fills the subscapular fossa; the serratus anterior inserts along the front of the medial border; both lie between the bone and the chest wall
Behind: Supraspinatus and infraspinatus in their fossae; the spine gives attachment to the middle trapezius and lower trapezius above and the rear deltoid below
Medial: Levator scapulae, rhomboid minor and rhomboid major on the medial border; the dorsal scapular nerve and artery run along it
Lateral: Long head of the triceps from the infraglenoid tubercle; teres minor and teres major from the lateral border, framing the quadrangular space (axillary nerve) and the triangular space (circumflex scapular artery)
Above: Coracoid process with the pectoralis minor, the short head of the biceps and the coracobrachialis; the suprascapular notch medial to its base

How to find it

The spine is followed from the acromion medially to its root at about the level of T3, and the inferior angle and medial border are felt with the arm relaxed. The coracoid process is felt by deep pressure just below the lateral third of the clavicle, in the deltopectoral groove; the acromion is the flat bony edge at the top of the shoulder.

Examination

Wall push-up: the medial border and inferior angle lift away from the chest wall in serratus anterior weakness (long thoracic nerve)
Resisted shoulder shrug and arm abduction: weakness with lateral winging and a drooping shoulder suggests spinal accessory nerve injury

On imaging

Shoulder trauma series: true AP of the glenohumeral joint, scapular Y view and axillary view. On the Y view the humeral head should sit over the centre of the Y (the glenoid); it lies in front in anterior dislocation and behind in posterior dislocation. CT with 3D reconstruction for glenoid and body fractures.

Common problems

Fractures are uncommon and usually come from high-energy trauma.
Poor control of the shoulder blade (scapular dyskinesis) can strain the shoulder.
Winging when the serratus anterior or trapezius nerve is injured.

How it is diagnosed

Exam of how the shoulder blade moves as the arm rises. X-rays and CT for fractures.

Treatment

Physical therapy to retrain the shoulder blade muscles.
Surgery only for fractures that involve the socket or are badly displaced.

Clinical notes

Suprascapular nerve compression at the suprascapular notch weakens supraspinatus and infraspinatus; at the spinoglenoid notch (often by a cyst from a labral tear) only infraspinatus is affected
Bony Bankart lesion: a fracture of the anterior-inferior glenoid rim after anterior dislocation; glenoid bone loss raises the risk of recurrent dislocation
The coracoid is a key surgical landmark: the brachial plexus and axillary vessels lie medial and deep to it

Anatomical variants

Os acromiale: an acromial ossification centre that never fused, often on both sides; it can mimic a fracture and is linked with impingement
Acromion shape varies (flat, curved, hooked); a hooked acromion is associated with subacromial impingement and rotator cuff tears

Development

The body ossifies before birth; the coracoid, the acromion (from several centres), the glenoid rim, the medial border and the inferior angle have secondary centres that fuse between late adolescence and the mid-twenties and can mimic fractures.

Memory aid

At the suprascapular notch: "the Army goes over the bridge, the Navy goes under" (artery over the ligament, nerve under it).

Test yourself

Think of the answer, then tap the question to see it.

At the suprascapular notch of the scapula, which structure passes under the suprascapular ligament and which passes above it?

The suprascapular nerve passes under the ligament and the suprascapular artery above it.

Medial winging of the scapula points to injury of which nerve and muscle?

The long thoracic nerve and the serratus anterior: the medial border and inferior angle lift off the chest, as on a wall push-up.

Lateral winging of the scapula with a drooping shoulder suggests injury of which nerve?

The spinal accessory nerve, which supplies the trapezius.

A scapular fracture should prompt a search for which associated injuries?

Rib fractures, pneumothorax, lung contusion and brachial plexus injury, because a scapular fracture marks high-energy trauma.

On the scapular Y view, where does the humeral head lie in anterior shoulder dislocation?

In front of the centre of the Y (the glenoid); in posterior dislocation it lies behind it.

Add to my cards (5)

Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): scapula TA2 1143
Official Spanish (DeCS): Escápula
English (TA2): Scapula
Also called: shoulder blade

Sources: Terminologia Anatomica (TA2); Anatomy, Thorax, Scapula.

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.

Scapula highlighted on the Durgical 3D model