Upper limb blood supply

One trunk, several names

The main artery of the upper limb is a single channel that changes its name each time it crosses a landmark.

• The nutrient artery of the humeral shaft comes from the brachial artery, entering near the middle of the bone; profunda brachii adds to it.
• The radial pulse is felt at the wrist lateral to the tendon of flexor carpi radialis, between it and brachioradialis, against the lower radius; it is also palpable in the anatomical snuffbox. In the forearm the artery runs under brachioradialis with the superficial branch of the radial nerve on its lateral side.
• The brachial artery lies medial to the humerus in the arm and can be compressed against it to control bleeding; blood pressure is measured over it at the elbow, medial to the biceps tendon.
• An injury at the outer border of the first rib involves the junction of the subclavian and axillary arteries, and the lower trunk of the brachial plexus lies right behind.
• Subclavian steal: a stenosis of the subclavian artery proximal to the vertebral origin lowers pressure beyond it; on arm exercise blood flows backwards down the vertebral artery to the arm, stealing from the brainstem and causing dizziness or syncope, with a weaker pulse and lower pressure in that arm.

Anastomoses: why ligation is survivable

An anastomosis is a communication between arteries; when one channel is blocked slowly or tied, the collaterals enlarge and keep the territory alive.

• The dorsal scapular artery is the direct branch of the subclavian that joins the scapular anastomosis; the suprascapular arrives indirectly through the thyrocervical trunk.
• If the brachial artery is cut or tied below profunda brachii, the forearm survives through the elbow anastomosis. Ligation above profunda is far riskier.
• Superficial palmar arch: its convexity lies about level with the distal border of the fully extended thumb, so surgeons mark it before palmar incisions (for example for Dupuytren disease). The deep arch is about 1 cm more proximal, across the metacarpal bases, and is mainly radial.
• Allen test: occlude both arteries at the wrist, let the hand blanch, then release the ulnar artery; colour returning within a few seconds shows an adequate ulnar supply through the arches before radial cannulation or harvest of the radial artery for coronary bypass.

Remember Deep arch is proximal and radial; superficial arch is distal and ulnar.

Superficial veins

• Both main veins start from the dorsal venous network of the hand.
• Cephalic vein: starts on the radial side, runs over the anatomical snuffbox (the "houseman's vein" for cannulation, close to the superficial radial nerve), up the lateral forearm and arm, through the deltopectoral groove, pierces the clavipectoral fascia and drains into the axillary vein. Used for venous cut-down and for pacemaker leads.
• Basilic vein: starts on the ulnar side, runs up the medial forearm, pierces the deep fascia in the middle of the arm, and joins the venae comitantes of the brachial artery to form the axillary vein at the lower border of teres major.
• Median cubital vein: links cephalic to basilic across the cubital fossa; the usual venepuncture site. The bicipital aponeurosis separates it from the brachial artery and median nerve.
• The axillary vein becomes the subclavian vein at the outer border of the first rib, passing in front of scalenus anterior, while the artery passes behind it.

Exam trap The cephalic vein runs in the deltopectoral groove and ends in the axillary vein; the basilic vein forms the axillary vein.

Effort thrombosis (Paget–Schroetter syndrome)

The subclavian vein crosses the first rib in the costoclavicular space, between the clavicle (with subclavius) and the first rib, in front of scalenus anterior. Repeated overhead or vigorous arm work narrows this space and injures the vein. A young athlete develops a swollen, bluish, heavy arm with dilated veins over the shoulder after intense training. Doppler shows axillary–subclavian thrombosis. It can embolise to the lungs, so it must not be dismissed as a muscle strain. It is the venous form of thoracic outlet syndrome.

Lymphatic drainage

• Superficial lymphatics follow the superficial veins. Those from the medial side of the hand and forearm (basilic territory) pass to the supratrochlear (cubital) nodes above the medial epicondyle, then to the lateral axillary nodes.
• Those from the lateral side (cephalic territory) run with the cephalic vein to the infraclavicular (deltopectoral) nodes and the apical axillary nodes.
• Deep lymphatics follow the deep arteries to the lateral (humeral) axillary group.
• All upper limb lymph ends in the axillary nodes and then the subclavian lymph trunk, so axillary clearance or radiotherapy can cause lymphoedema of the arm. An infected little finger or ulnar border may give a tender supratrochlear node.

Clinical points

Exam trap Pulses may be felt in early compartment syndrome, because compartment pressure falls short of arterial pressure while still blocking capillary flow.

How FCPS asks about this

• Direct subclavian branch in the scapular anastomosis: dorsal scapular artery; suprascapular comes via the thyrocervical trunk.
• Where the axillary artery becomes brachial: lower border of teres major; subclavian becomes axillary at the outer border of the first rib.
• Brachial artery tied or cut below profunda: limb survives through the elbow anastomosis.
• Superficial palmar arch level: distal border of the extended thumb; deep arch 1 cm proximal and mainly radial.
• Effort thrombosis in a weightlifter: subclavian vein compressed between the clavicle and first rib (Paget–Schroetter).
• Course of the cephalic vein: lateral arm, deltopectoral groove, clavipectoral fascia, axillary vein.
• Dizziness on arm exercise: subclavian steal; reversed flow in the vertebral artery.