Arterial Anastomoses of the Upper Extremity
Throughout the body, there are several points at which blood vessels unite. The junctions are termed anastomoses. In the simplest sense, an anastomosis is any connection (made surgically or occurring naturally) between tube-like structures. Naturally occurring arterial anastomoses provide an alternative blood supply to target areas in cases where the primary arterial pathway is obstructed. They are most abundant in regions of the body where the blood supply may can be easily damaged or blocked (such as the joints or intestines). This article focuses on the arterial anastomotic networks of the upper limb.
Scapular & Shoulder Anastomoses
There is a vast network of anastomotic vessels in the scapular and shoulder regions of the upper limb. They are perfectly positioned to provide surrogate blood supply in instances of vascular compromise. The branches of the scapular anastomoses come from the subclavian artery and the axillary artery. Those of the shoulder are derived from the different segments of the axillary artery.
The first member of the scapular anastomoses arises from the thyrocervical trunk. The suprascapular artery travels posterolaterally across the omohyoid muscle, then over the superior transverse scapular ligament. Shortly afterwards, it gives one branch that courses along the supraspinous fossa and another that travels inferomedially around the spine of the scapula to enter the infraspinous fossa.
The second contributing artery also branches from the subclavian artery. It is the dorsal scapular artery, which splits to give a branch that travels medial to the levator scapulae muscle, and another that passes inferiorly and courses along the medial border of the scapula.
The circumflex scapular artery branches from the subscapular artery (from the third part of the axillary artery) and becomes the third contributing part of the scapular anastomoses. It courses around the lateral border of the scapula to enter the infraspinous fossa.
The suprascapular and dorsal scapular arteries meet in the supraspinous fossa to form an anastomosis. While the circumflex scapular artery and infraspinous branch of the suprascapular artery anastomose with each other, they also join with branches of the dorsal scapular artery that pierce the infraspinatus muscle to enter the infraspinous fossa.
Around the surgical neck of the humerus and the glenohumeral joint, there are anastomotic contributions coming from the second and third part of the axillary artery. The acromial branch of the thoraco-acromial artery (2nd part of axillary artery) travels superolaterally towards the acromion. At the acromion of the scapula, it meets the acromial branches of the circumflex humeral arteries (3rd part of axilla) and the suprascapular artery too for its anastomosis.
The posterior circumflex humeral artery also anastomoses with the anterior circumflex humeral artery around the surgical neck of the humerus. Below the level of teres major, where the axillary artery becomes the brachial artery, the profunda brachii artery is given off. Its recurrent branch goes on to form an anastomosis with the descending branch of the posterior circumflex humeral artery.
Both profunda brachii and the brachial artery give important branches that form the elbow anastomoses. On the posterior aspect of the shaft of the humerus, profunda brachii branches into a middle and a radial recurrent artery. The brachial artery gives off a superior ulnar collateral artery (about 1-2 cm below profunda brachii) and an inferior ulnar collateral artery (about 1 cm above the medial supracondylar ridge).
At the lateral supracondylar ridge, the radial collateral artery bifurcates. One branch travels posterior to the humerus, where it anastomoses with the middle collateral artery, the recurrent interosseous artery (from the posterior interosseous artery) and the posterior branch of the inferior ulnar collateral artery.
In the deep antecubital fossa, the radial recurrent artery (from the radial artery) anastomoses with the radial collateral artery; while the anterior and posterior ulnar recurrent arteries anastomose with the inferior and superior ulnar collateral arteries, respectively. There is also a communication between the posterior ulnar recurrent artery and the posterior branch of the inferior ulnar collateral artery.
Wrist & Hand Anastomoses
The wrist and hand receives arterial supply from three anastomosing sources: the radial artery, the ulnar artery and the interosseous arteries. The anterior interosseous artery communicates with the posterior interosseous artery through a hiatus in the distal part of the interosseous membrane. The vessel continues distally before bifurcating at the level of the lunate bone.
The radial artery also bifurcates, but at the level of the styloid process of the radius. Here, it gives contributions to the deep and superficial palmar arches. The ulnar artery divides twice: first at the level of the styloid process of the ulna, and secondly on the radial side of the hook of the hamate bone.
The first ulnar bifurcation gives the dorsal carpal artery. As its name suggests, the artery travels along the dorsal part of the carpal bones to communicate with the most radial (most lateral when the hand is supine) branch of the radial artery (prior to its division to form princeps pollicis, radialis indicis and the deep palmar arch). The second ulnar bifurcation gives rise to the branches of the superficial and deep palmar arches. Both the superficial and deep palmar arches give rise to three palmar metacarpal arteries. These short arterial branches unite at the metacarpophalangeal joints to form the 3rd, 4th and 5th common palmar digital arteries.
Traumatic insults to the upper extremity (fractures, stab wounds or gunshot wounds) can result in dramatic blood loss. It is important for the clinician to understand the arterial anastomoses in the affected area so that bleeding can be appropriately managed and exsanguination can be avoided.