VASCULAR ANATOMY OF THE EXTREMITIES

CHAPTER 62 VASCULAR ANATOMY OF THE EXTREMITIES



Enrique Ginzburg, Chee Kiong Chong, Norman M. Rich


Extremity vascular injuries date as far back as the Greek and Roman civilization. Much of the knowledge regarding vascular trauma and the management of these injuries was gained from military conflicts. DeBakey and Simeone reported the amputation rate to be as high as 40% in World War II, when it was the main life-saving measure for soldiers who sustained extremity injuries. With the advance in surgical technologies and techniques, the rate of amputation dropped to as low as 15% during the Korean War. All this information provides modern surgeons with the ability to manage vascular trauma without the need to enter a combat zone.



DIAGNOSIS


Most patients that are admitted to a trauma center with extremity vascular injuries will be admitted from penetrating trauma. These are usually either stab wounds from knives or low velocity bullet wounds. In most cities, this is closely followed by patients who sustain blunt injuries as a result of motor vehicle crashes, and these are often associated with long bone fractures.


There are hard and soft clinical signs of vascular trauma. The hard signs include the following:


Pulsatile bleeding

Absence of pulses

Distal ischemia

Visible expanding or pulsatile hematoma

Presence of a thrill or bruit over the injured site

The soft signs of vascular injury include the following:


Bony injury

Proximity of penetrating wound

Presence of significant hemorrhage but stopped

Neurologic deficit

Well-contained hematoma

Swelling out of proportion to the injury

Patients with hard signs of vascular injury will undergo mandatory surgical exploration, as any delay will increase the risk of amputation, reperfusion injury, compartmental syndrome, and infection. The management of patients with soft signs will usually include further diagnostic studies, close observation, and frequent re-examination. Diagnostic studies include Doppler ultrasound, computed tomography (CT) angiogram, or conventional angiography.



MANAGEMENT


The management of patients appearing with obvious peripheral vascular injuries should follow the protocols outlined by Advance Trauma Life Support (ATLS). Airway, breathing, and circulation will take priority. Injury to the brain, chest, and abdomen will also usually take precedence over extremity hemorrhage, which can usually be controlled by direct pressure.


Successful management of extremity vascular injury includes the following components:


Prompt resuscitation

Control of hemorrhage, usually with direct pressure

Timely diagnosis

Early surgical exploration

Minimized delay in transporting patient to operating room or extensive diagnostic studies when not indicated

A thorough knowledge of the relevant anatomy of the extremity is very important during surgical exploration. Destruction or distortion of tissue planes by hemorrhage is usually the rule rather than the exception, and when this is coupled with the retraction of the vessels into the surrounding tissue, it will increase the difficulty of achieving proximal and distal control of the bleeding vessel, which is the most important step in stopping the bleeding.



VASCULAR ANATOMY OF UPPER EXTREMITY



Axillary Artery


The axillary artery starts from the lateral border of the first rib, as a direct continuation of the subclavian artery. It enters the axilla at the apex and crosses the first intercostal space to run along the lateral wall of the axilla. As the artery emerges from beneath the costoclavicular passage, it becomes closely related to the brachial plexus, divisions, and cords. These nerves surround the artery and exchange fibers to eventually become the median, ulnar, and radial nerves at the distal portion of the axillary artery. This neurovascular bundle is enclosed in the axillary sheath, which separates it from the axillary vein. Distally, the axillary artery continues on as brachial artery at the lateral edge of the teres major muscle tendon.


Anteriorly, the axillary artery follows a course under the pectoralis minor muscle as it inserts into the coracoid process. The muscle divides the artery into three anatomical portions:


The first portion runs from lateral edge of the first rib to the upper border of the tendon pectoralis minor muscle, behind the clavipectoral fascia and the clavicular head of the pectoralis major muscle. It has only one branch in this portion, the supreme thoracic artery.


The second portion lies behind the pectoralis minor muscle. This is the shortest portion and it has two branches of clinical significance, the thoracoacromial artery and the lateral thoracic artery. The cords of the brachial plexus surround the axillary artery at this section.


The third portion starts from the lateral border of the pectoralis muscle to the lateral border of the teres major muscle. The axillary artery gives out three branches at the portion, the subscapular artery, the lateral humeral circumflex artery, and the medial circumflex artery. At this level, the brachial plexus becomes the medial nerve, which is anterior, the radial nerve, which is posterior, and the ulnar nerve, which is inferior to the axillary in the axillary sheath.



Axillary Vein


The basilic vein continues on at the lower edge of the teres major muscle as the axillary vein. Its main tributaries are brachial veins, which accompany the named arteries while they ascend in the axilla, and the cephalic vein, which courses through the deltopectoral groove, just below the clavicle. The axillary vein then becomes the subclavian vein above the lateral border of the first rib.


The axillary vein lies medial to the axillary artery. It is separated from artery by the medial pectoral nerve, medial cord of the brachial plexus, and the ulnar nerve. It is separated from the axillary sheath by a pad of fat. The close proximity of the vein to the artery often results in the occurrence of traumatic arteriovenous malformations. Penetrating injury to the upper part of axilla can cause profuse hemorrhage and risk of air embolism.



Surgical Exposure of Axillary Vessels


The axillary artery lies anterior to the capsule of the shoulder joint and might be injured when the shoulder is dislocated anteriorly. Fractures of the surgical neck of the humerus will also risk lacerating the vessel as it runs over the fusion of the subscapularis tendon and the joint capsule.


The axillary artery can be exposed through an infraclavicular incision placed 2 cm below and parallel to the mid-point of the clavicle, following a gentle curve along the anterior axillary line and then along the anterior border of the deltoid muscle. The first portion of the artery is the simplest to expose because it is medial to the pectoralis muscle and contains only one branch. Exposure of the second portion will require the detachment of the pectoralis minor tendon from the coracoid process. The cords of the brachial plexus surround this portion of the axillary artery, arranged medially, laterally, and posteriorly. From the posterior cord arises the axillary nerve, which follows a posterolateral course on the neck of the humerus. This nerve can be easily injured by dislocation of the humerus or fracture of the surgical neck, causing atrophy of the deltoid muscle and numbness of an area over the deltoid region. The third portion becomes superficial after emerging from under the pectoralis major muscle before becoming the brachial artery. Great care must be taken while exposing this portion because the nerves to the upper extremities run about it. The median nerve runs anterior to the artery and is frequently involved in axillary injuries resulting from its superficial position.



Brachial Artery


The brachial artery originates at the lower border of the teres major muscle as a direct continuation of the axillary artery. It takes a course toward the antecubital fossa, together with the median nerve, and bifurcates into radial and ulnar arteries opposite the neck of the radius. The medial bicipital sulcus, which separates the coracobrachialis and biceps muscle anteriorly from the triceps muscle posteriorly, marks the course of the basilic vein toward the axillary vein and provides the surface marking of the brachial vessels.


The proximal part of the brachial artery lies on the medial aspect of the arm, anterior to the long and median head of the triceps and bordered laterally by the coracobrachialis muscle. The median nerve lies between the coracobrachialis muscle and the brachial artery, whereas the ulnar nerve separates the artery from the basilic vein. The brachial artery gives rise to the profunda brachii artery posteriorly, which passes backward and accompanies the radial nerve in the radial groove to the lateral condyle of the humerus. This artery collateralizes about the shoulder with the circumflex humeral arteries arising from the axillary artery.


The brachial artery gradually inclines forward and outward and eventually comes to lie below the medial border of the biceps muscle. The median nerve crosses the artery obliquely at this part of the arm. The basilic vein and the medial cutaneous nerve are separated from the artery by the deep fascia sheath. The branches arising from this portion of the brachial artery include the nutrient artery to the humerus, muscular branches, and superior ulnar collateral artery, which accompanies the ulnar nerve to the groove on the posterior surface of the medial epicondyle. This artery subsequently takes part in the rich anastomosis around the elbow joint.


The distal part of the brachial artery is overlapped by the medial border of the biceps muscle and biceps tendon and eventually comes to lie medial to the biceps tendon before the bifurcation of the artery. The median nerve lies medial to the brachial artery. This inferior ulnar collateral artery arises near the elbow and forms a rich network of collaterals around the elbow joint. Brachial artery bifurcates opposite the neck of the radius bone to give rise to the ulnar artery medially and the radial artery laterally.


The artery is closely accompanied by a pair of venae comitantes that drain into the axillary vein.



Surgical Exposure of Brachial Artery


The brachial artery is the most commonly injured artery in the upper extremity, probably as a result of the superficial course that it takes. This artery accounts for 50% of all upper extremity injuries.


In the arm, exposure in any part of the artery can be achieved by a longitudinal incision along the course of the vessel just medial to the bicipital sulcus. This sulcus can be easily identified by grasping the head of the biceps and lifting it up to reveal the groove. The artery, along with the accompanying vein and nerves, is immediately visible after dividing the skin and subcutaneous tissue, investing the fascia, and splitting the biceps and triceps muscle. The basilic vein runs a superficial course along the bicipital sulcus. It can be identified and retracted laterally to prevent injury to the vein.


Just above the elbow, the brachial artery passes behind the bicipital aponeurosis, which may be divided to facilitate exposure of the vessel. The brachial artery is juxtaposed to the median nerve. Extension of incision across the antecubital fossa should be made with an S-shaped incision to reduce the risk of joint contracture. Care has to be exercised to prevent injury to the accompanying nerves and veins.



Radial Artery


The radial artery is usually the smaller branch that follows the general direction of the brachial artery. It is a fairly superficial vessel, covered mainly by skin, subcutaneous tissue, and fascia, save for the upper part, which is covered by the fleshy belly of brachioradialis muscle. The artery takes a course that travels laterally gradually, and after emerging from under the brachioradialis muscle, it comes to lie between the brachioradialis and the flexor carpi radialis muscles. The distal part, which is the most superficial part of the radial artery, travels between the tendon of flexor pollicis longus and the lateral border of the radius, until it passes behind the flexor retinaculum to enter the hand.


The radial artery gives rise to two major branches, the radial recurrent branch near the origin, and the superficial palmar branch, which takes part in the formation of the superficial palmar arch.



Ulnar Artery


The ulnar artery is the larger of the two terminal trunks of the brachial artery. It runs downward and medially to reach the medial aspect of the forearm from the bifurcation. During its course, the artery lies on the brachialis muscle in the upper part and then on the flexor digitorum profundus as it progresses distally. It is covered by the pronator teres muscle, flexor carpi radialis, and flexor digitorum superficialis. The medial nerve lies medial to the ulnar artery for the first 2.5 cm before it crosses in front of the artery to take up a lateral relationship. After the crossing over, the nerve is separated from the artery by the ulnar head of the pronator teres.


At the distal part, the ulnar artery emerges between the tendon of the flexor digitorum superficialis medially and flexor carpi ulnaris laterally to be covered by skin and fascia only. It subsequently passes behind the palmaris brevis to terminate in the superficial palmar arch. The branches that give out near the origin of the ulnar artery include the anterior and posterior ulnar recurrent arteries and the common interosseous artery.

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Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on VASCULAR ANATOMY OF THE EXTREMITIES

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