Scapula and Clavicle Anatomy
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Direct answer
Two bones suspend each upper limb from the trunk: the clavicle, a horizontal strut from manubrium to acromion, and the scapula, a flat triangular plate riding on the posterior thoracic wall over the second to seventh ribs. The clavicle is the first bone in the body to ossify (fifth to sixth intrauterine week) and the only long bone ossified in membrane, yet it is also the commonest fractured bone, breaking at its middle third where the sternocleidomastoid pulls the medial fragment upwards. The scapula's ligamentous gateways matter more than its shape — the suprascapular nerve runs below the superior transverse scapular ligament while the artery crosses above it, and the same nerve is picked off again at the spinoglenoid notch.
What you must remember
- Clavicle landmarks: convex forward medially, concave laterally; the nutrient foramen near its middle third; inferior surface carries the groove for subclavius and, laterally, the conoid tubercle and trapezoid line for the coracoclavicular ligament.
- Clavicle fracture mechanics: middle third in about 80 per cent; the medial fragment rides up (sternocleidomastoid) while the shoulder drops (deltoid and arm weight) — overriding fragments on the radiograph, yet union is the rule.
- Ossification pair worth quoting: first bone to begin ossifying, and its medial epiphysis is among the last to fuse (about 25 years) — a classic MCQ couplet.
- Scapular processes: spine with acromion laterally, and the coracoid process jutting forwards — pectoralis minor, short head of biceps and coracobrachialis attach at its tip.
- Glenoid margins: long head of biceps from the supraglenoid tubercle, long head of triceps from the infraglenoid tubercle — both intra-articular, both torn in shoulder dislocation.
- Notch rule: at the suprascapular notch the artery passes above the superior transverse scapular ligament and the nerve below it — army over navy; at the spinoglenoid notch the bare nerve curves into infraspinatus territory.
- Muscle map: rotator cuff on the tubercles, trapezius and deltoid on the spine and acromion, levator scapulae and rhomboids on the medial border, serratus anterior on the costal surface holding the scapula against the chest.
- Winged scapula: serratus anterior paralysis after long thoracic nerve (C5, C6, C7) injury — the classical neurological complication of axillary surgery and radical mastectomy.
One motorcyclist, two bones
A young man is thrown onto the point of the shoulder. The middle third of the clavicle snaps, and the deformity explains itself: the trapezius can no longer hold the lateral fragment, the arm's weight drags the shoulder down and in, and the sternocleidomastoid tents the medial fragment under the skin. Treatment is a sling or figure-of-eight bandage, and the prominent bump remodels — clavicle fractures unite even when imperfectly apposed, a fact worth stating before describing the rare indications for fixation. Had the same force driven the humeral head down instead, the picture shifts to the scapula's muscle envelope: scapular fractures are themselves a marker of high-energy trauma, and the examiner's follow-up is the neurological pair nearby — the suprascapular nerve at the notch wasting both supraspinatus and infraspinatus, or at the spinoglenoid notch sparing supraspinatus and isolating infraspinatus, an anatomical discrimination between two sites of one nerve.
How the viva unfolds
Expect the clavicle first: its unique features list — first to ossify, membranous ossification, the only long bone that lies horizontally, no obvious medullary cavity, and fracture commonest in childhood. Then the scapula is placed before you for siding: the glenoid faces laterally, the costal surface is concave with the serratus markings, and the spine runs backwards. The army-over-navy rule at the suprascapular notch is the standard trap; the sharper follow-up asks what the suprascapular nerve supplies, and candidates who name only supraspinatus lose half the mark — it supplies both cuff muscles on the posterior aspect, and its injury mimics a rotator cuff tear with weakness of abduction and external rotation.
Frequently asked questions
Which is the commonest site of clavicular fracture and what is the deformity?
The middle third, where two curvatures meet. The medial fragment is elevated by sternocleidomastoid and the lateral fragment drops with the shoulder, producing overlap and a palpable bump.
Which structures pass above and below the superior transverse scapular ligament?
The suprascapular artery above, the suprascapular nerve below — the artery over the nerve, army over navy. The ligament can ossify and entrap the nerve.
Which nerve injury causes a winged scapula?
The long thoracic nerve of Bell (C5-C7) paralysing serratus anterior, seen after mastectomy or axillary node dissection. The medial border lifts off the chest wall on pushing against a wall.
Why is the clavicle described as a unique long bone?
It is the first bone to ossify (about the fifth intrauterine week), ossifies largely in membrane, lies horizontally, and its medial epiphysis is among the last to fuse at about 25 years.
Which structures attach to the coracoid process?
Pectoralis minor, the short head of biceps and coracobrachialis on the tip, plus the coracoclavicular, coracoacromial and coracohumeral ligaments — a fountain of structures flowing from one process.