ARTERIES OF THE UPPER LIMB - THEIR MAIN ANASTOMOSES

Detailed Study Notes

1. AXILLARY ARTERY - Parts, Topography, Branches

Definition and Boundaries

Three Parts (Divided by Pectoralis Minor)

Relations

• Enclosed within the axillary sheath along with the brachial plexus cords
• The lateral cord is lateral, the medial cord is medial, and the posterior cord is posterior to the artery
• The axillary vein lies medially

Branches and Blood Supply (by Triangle)

1. Superior thoracic artery - small; supplies the upper intercostal spaces, upper parts of the medial and anterior axillary walls, and the serratus anterior

• Pectoral branch - supplies pectoralis major and minor; contributes to breast supply
• Deltoid branch - travels with the cephalic vein in the deltopectoral groove; supplies deltoid and pectoralis major
• Clavicular branch - supplies clavicular part of pectoralis major and the sternoclavicular joint
• Acromial branch - contributes to the acromial anastomosis

1. Lateral thoracic artery - runs along the lateral border of pectoralis minor; supplies the serratus anterior, pectoralis muscles, and the breast (especially in females)

• Circumflex scapular artery - passes through the triangular space; supplies the infraspinous fossa; anastomoses with suprascapular artery
• Thoracodorsal artery - continues to supply latissimus dorsi, serratus anterior, and subscapularis

1. Anterior circumflex humeral artery - smaller; circles the surgical neck of the humerus anteriorly; supplies the glenohumeral joint and the head of the humerus
2. Posterior circumflex humeral artery - larger; passes through the quadrangular space with the axillary nerve; wraps around the surgical neck of the humerus posteriorly; supplies the deltoid, shoulder joint capsule, teres minor, and head of humerus

Anatomical variant note (THIEME Atlas): The normal branching pattern (as above) occurs in ~40% of cases. Common variants include: posterior circumflex humeral artery from subscapular artery (20%), common origin of anterior and posterior circumflex humeral arteries (20%), and thoracoacromial arising from the lateral thoracic artery (10%).

2. BRACHIAL ARTERY - Topography and Branches

Course

• Begins as the continuation of the axillary artery at the lower border of teres major
• Terminates just distal to the elbow joint where it divides into the radial and ulnar arteries (at the level of the radial neck, within the cubital fossa)
• Runs in the anterior compartment of the arm throughout its course

Topography at Different Levels

• Proximal arm: lies on the medial side of the humerus, on the medial surface of the coracobrachialis, then on the brachialis muscle
• Middle arm: lies medial to the biceps brachii, accompanied by the median nerve (which crosses it from lateral to medial)
• Distal arm / cubital fossa: moves to a midpoint between the two epicondyles; lies medial to the biceps tendon and anterior to the elbow joint. The bicipital aponeurosis crosses over it superficially, separating it from the median cubital vein
• The artery is palpable along its entire length; in the proximal arm it can be compressed against the medial surface of the humerus

Branches of the Brachial Artery

1. Profunda brachii artery (deep artery of the arm) - largest branch; see Question 4
2. Superior ulnar collateral artery - arises from the middle of the arm; accompanies the ulnar nerve posterior to the medial epicondyle; joins the ulnar anastomotic network around the elbow
3. Inferior ulnar collateral artery - arises just above the elbow; runs anterior to the medial epicondyle; joins the arterial network of the elbow
4. Nutrient arteries to the humerus - pass through a foramen in the anteromedial humeral shaft
5. Muscular branches - to the coracobrachialis, biceps brachii, and brachialis

3. BLOOD SUPPLY OF THE SHOULDER JOINT - Arterial Rete

4. DEEP ARTERY OF THE ARM (Profunda Brachii) - Topography and Humero-Muscular Canal

Origin and Initial Course

• Arises from the posterolateral aspect of the brachial artery just below the lower border of teres major - it is the largest branch of the brachial artery
• Accompanies the radial nerve

Course Through the Humero-Muscular (Radial) Canal

• Passes through the triangular interval (bounded by: shaft of the humerus superiorly, inferior margin of teres major, lateral margin of the long head of triceps)
• Enters the radial groove (humero-muscular canal) on the posterior surface of the humerus, passing deep to the lateral head of the triceps brachii
• This canal is formed between the humerus and the overlying triceps muscle

Branches

1. Muscular branches - to the triceps brachii (all three heads)
2. Nutrient branch - to the humerus
3. Deltoid branch - anastomoses with the posterior circumflex humeral artery
4. Radial collateral artery (terminal branch) - passes anterior to the lateral epicondyle; anastomoses with the radial recurrent artery (from radial artery) in front of the lateral epicondyle
5. Middle collateral artery (terminal branch) - passes posterior to the lateral epicondyle; anastomoses with the interosseous recurrent artery (from posterior interosseous artery)

Clinical note: The radial nerve travels with the profunda brachii artery in the radial groove. A fracture of the middle third of the humerus (at the lateral intermuscular septum) can damage both the artery and the nerve simultaneously.

5. RADIAL ARTERY - Topography and Branches

Origin

Topography in the Cubital Fossa

• Lies under the brachioradialis muscle in the lateral part of the cubital fossa
• Covered by the bicipital aponeurosis

Course in the Forearm

• Runs along the anterior (flexor) surface of the forearm under the brachioradialis muscle
• In the lower two-thirds of the forearm it lies on the anterior surface of the radius, lateral to the flexor carpi radialis tendon - palpable here as the radial pulse
• Passes over the styloid process and enters the anatomical snuffbox (palpable there too), running on the scaphoid and trapezium deep to the extensor pollicis longus and brevis tendons
• Enters the deep plane of the palm by passing between the two heads of the first dorsal interosseous muscle, then between the heads of adductor pollicis

Branches of the Radial Artery

6. ULNAR ARTERY - Topography and Branches

Origin

Topography in the Cubital Fossa

• Passes deep to the pronator teres and the common flexor origin
• Passes deep to flexor digitorum superficialis (between the two heads of that muscle alongside the median nerve)

Course in the Forearm

• Initially runs deep, then becomes more superficial
• In the lower two-thirds of the forearm: lies between the flexor digitorum superficialis (laterally) and flexor carpi ulnaris (medially)
• Accompanied by the ulnar nerve (nerve is medial to the artery throughout the forearm)
• Passes superficial to the flexor retinaculum, lateral to the pisiform, through Guyon's canal (ulnar tunnel), between the palmar carpal ligament and flexor retinaculum

Branches of the Ulnar Artery

7. BLOOD SUPPLY OF THE ELBOW JOINT - Arterial Rete

Medial Side of the Elbow

Lateral Side of the Elbow

8. INTEROSSEOUS ARTERIES - Level of Origin and Blood Supply

Common Interosseous Artery

• Branch of the ulnar artery arising in the proximal forearm just below the radial tuberosity
• Short trunk that immediately divides into:

Anterior Interosseous Artery

• Course: Descends along the anterior surface of the interosseous membrane between flexor pollicis longus (lateral) and flexor digitorum profundus (medial), accompanied by the anterior interosseous nerve
• Supply: Flexor pollicis longus, flexor digitorum profundus, pronator quadratus, radius, ulna, nutrient arteries to both bones
• Terminates: Pierces the interosseous membrane in the distal forearm to reach the dorsal carpal network; sends a branch to the palmar carpal network

Posterior Interosseous Artery

• Course: Passes over the proximal margin of the interosseous membrane (or through a hiatus) to reach the posterior compartment of the forearm; descends between the superficial and deep layers of extensor muscles, accompanied by the posterior interosseous nerve
• Gives off the recurrent interosseous artery proximally, which ascends to anastomose with the middle collateral artery at the elbow (contributes to elbow network)
• Supply: All muscles of the posterior compartment of the forearm, dorsal aspect of the wrist
• Terminates: Anastomoses with the dorsal carpal network from the radial artery

9. SUPERFICIAL PALMAR ARCH - Formation, Topography, Branches

Formation

• Arch arises entirely from the ulnar artery in ~37% of cases
• Ulnar + radial (classical) in the majority
• Rarely completed by the median artery (a persistent embryological vessel)

Topography

• Lies superficial to the long flexor tendons (FDS and FDP tendons)
• Deep to the palmar aponeurosis only
• Convexity points toward the middle finger (level of the distal border of the outstretched thumb)
• Lies in the superficial plane of the palm

Branches

1. Proper palmar digital artery to the medial side of the little finger
2. Three common palmar digital arteries (for the 2nd, 3rd, and 4th web spaces) - each receives a palmar metacarpal artery from the deep arch before dividing into proper palmar digital arteries that supply:
   • Lateral side of the little finger
   • Both sides of the ring and middle fingers
   • Medial side of the index finger
3. The lateral side of the index finger and both sides of the thumb are typically supplied by branches of the deep arch (princeps pollicis, radialis indicis)

10. DEEP PALMAR ARCH - Formation, Topography, Branches

Formation

Course of the Radial Artery to Form the Deep Arch

• Passes through the anatomical snuffbox
• Passes between the two heads of the 1st dorsal interosseous muscle
• Passes between the two heads of the adductor pollicis
• Enters the deep plane of the palm - forms the arch

Topography

• Located in the deep plane of the palm, between the metacarpal bones and the long flexor tendons
• Lies on the bases of the metacarpals and the interosseous muscles
• Deep to the flexor tendons and lumbricals

Branches

1. Three palmar metacarpal arteries (in the 2nd, 3rd, and 4th metacarpal spaces) - descend to join the common palmar digital arteries of the superficial arch
2. Perforating branches - three pairs that pass dorsally through the interosseous spaces to anastomose with the dorsal metacarpal arteries
3. Recurrent branches - contribute to the palmar carpal network (anastomose with palmar carpal branches of radial and ulnar arteries)

11. BLOOD SUPPLY TO THE WRIST JOINT - Arterial Rete

Palmar Carpal Network (Rete Carpale Palmare)

• Palmar carpal branch of the radial artery
• Palmar carpal branch of the ulnar artery
• Terminal branch of the anterior interosseous artery
• Recurrent branches of the deep palmar arch

Dorsal Carpal Network (Rete Carpale Dorsale)

• Dorsal carpal branch of the radial artery (passes medially across the wrist)
• Dorsal carpal branch of the ulnar artery
• Terminal branch of the posterior interosseous artery (and anterior interosseous artery perforator)

From the Dorsal Carpal Arch

• Gives off 3-4 dorsal metacarpal arteries, which divide at the webs into dorsal digital arteries supplying the dorsal aspects of the fingers (proximal and middle phalanges; distal phalanges supplied by palmar digital arteries)

12. FEATURES OF BLOOD SUPPLY TO THE THUMB (Pollicis)

Arterial Supply

• Princeps pollicis artery (main supply) - arises from the radial artery as it passes between the heads of the 1st dorsal interosseous and adductor pollicis; divides into:
  • Radial palmar digital artery of the thumb (to radial side)
  • Ulnar palmar digital artery of the thumb (to ulnar side)
• Superficial palmar branch of the radial artery may also contribute a small branch

Features

1. The thumb's blood supply is predominantly from the radial artery (via princeps pollicis), in contrast to the fingers which are mainly supplied by the ulnar artery via the superficial palmar arch
2. The dorsum of the thumb is supplied by the first dorsal metacarpal artery (from radial artery in the snuffbox) and its terminal branch to the dorsal aspect
3. There is rich anastomosis between the palmar and dorsal systems at the thumb
4. This is why the radial pulse is monitored before any procedure on the radial artery at the wrist (e.g., radial artery catheterization) - to ensure adequate collateral supply via the ulnar artery through the palmar arches

13. COLLATERAL BLOOD SUPPLY AND RATIONALE FOR LIGATION

Collateral Blood Supply of the Upper Limb

• Superior and inferior ulnar collateral arteries + anterior and posterior ulnar recurrent arteries (medial side)
• Radial collateral + radial recurrent arteries (lateral side)
• Middle collateral + interosseous recurrent arteries (posterior)

• Superficial and deep palmar arches interconnect radial and ulnar systems
• Dorsal and palmar carpal networks provide multiple anastomotic channels at the wrist

Anatomical Rationale for Ligation of Major Vessels

Ligation of the Brachial Artery

• Safe level: Above the origin of the profunda brachii - collateral circulation through the anastomoses around the scapula and shoulder is sufficient if the shoulder anastomosis is intact
• Dangerous level: Below the origin of the profunda brachii - the profunda brachii terminates as the radial and middle collateral arteries, which anastomose with the radial recurrent and interosseous recurrent arteries at the elbow - but the volume of collateral flow may be insufficient
• Below the inferior ulnar collateral artery: Most dangerous - the collateral network at the elbow relies on both the profunda brachii collaterals and the ulnar collaterals; ligation here significantly reduces collateral capacity
• Clinical principle: The brachial artery can be ligated above the profunda brachii with reasonable safety because the scapular anastomoses provide retrograde flow. Ligation below the origin of the profunda brachii carries significant risk of ischemia to the forearm and hand.

Ligation of the Radial Artery

• Safe: Can generally be ligated anywhere in the forearm because the dual blood supply to the hand (via both radial and ulnar arteries connecting through both palmar arches) means the ulnar artery alone can supply the hand
• Prerequisite: An intact ulnar artery and intact palmar arches must be confirmed (Allen's test)
• The deep palmar arch (from radial artery) can receive retrograde flow from the ulnar artery via the deep palmar branch
• Common clinical use: Radial artery is routinely harvested for coronary artery bypass grafts with good outcomes

Ligation of the Ulnar Artery

• Generally safe in the forearm because the radial artery can supply the hand via both palmar arches
• The superficial arch (predominantly ulnar) can receive contributions via the superficial palmar branch of the radial artery
• Less safe at Guyon's canal level (wrist) - if ligated here before it contributes to the superficial arch, the hand depends entirely on the radial artery
• The dual supply of the hand (through both arches and their anastomoses with each other and the interosseous system) provides the rationale for safe ligation of either vessel alone, but not both simultaneously

Summary table for ligation:

Key Images to Know

• Fig. 7.49/7.50 - Axillary artery parts and branches
• Fig. 7.66A/B - Brachial artery and profunda brachii in the arm
• Fig. 7.77 - Cubital fossa contents (brachial artery bifurcation, radial nerve, bicipital aponeurosis)
• Fig. 7.109/7.110/7.111 - Deep and superficial palmar arches
• THIEME Atlas Fig. 5.6E - Axillary artery variants (pg. 404)
• THIEME Atlas pg. 421 - Superficial and deep palmar arch diagrams with variants