Subclavian vessel injuries: Difficult anatomy and difficult territory

Historical perspective

Halsted in 1892 performed the first successful subclavian aneurysmal ligation. Given the infrequent occurrence of subclavian vessel injuries, surgeons had minimal experience in their management prior to wartime. Commonly the general practice was simple ligation. During World War I, the American and British surgeons estimated the overall rate of vascular injury to range from 0.4% to 1.3%. In 1919, Makins reported 45 subclavian artery injuries among British casualties during World War I. A landmark study from DeBakey and Simeone in 1946 reported an incidence of less than 1%, accounting for 21 patients of 2471 arterial injuries sustained by American soldiers during World War II. During the Korean conflict, Hughes’s study of 304 major arterial vessel injuries reported only three subclavian artery cases. The relatively few cases throughout the history of war may account for exsanguination on the battlefield. Penetrating subclavian injuries accounted for less than 1% of all vascular injuries reported during the Vietnam conflict. During this time, 48 different surgeons treated this injury; only two encountered this injury more than once, for a total of 68 reported cases. Rich reported a total of 63 subclavian artery injuries in the original report of the Vietnam Vascular Registry for acute arterial vascular injuries during the Vietnam War.

During the recent conflicts of Iraq and Afghanistan, the overall rate of vascular injury was reported to be greater than in previously reported conflicts. This increase in rate may be related to improved hemorrhage control, shorter evacuation times, and improved survivability. High-velocity injuries from explosives and gunshot wounds accounted for the majority of these injuries. Interestingly, the incidence of vascular injury was higher in Iraq than in Afghanistan, 12.5% and 9%, respectively. White et al identified 1570 U.S. troops, in both Iraq and Afghanistan, who presented with war-related vascular injuries. Of these, 12% resulted in vascular injuries of the torso, with subclavian vessel injuries accounting for 2.3%. Over a 24-month period, Clouse et al identified 301 arterial vascular injuries, of which 3.7% were due to subclavian-axillary vessel injury. Nevertheless, both the management and treatment strategies have evolved from the various wars and battlefields over the course of time ( Table 1 ).

Anatomy

The subclavian arteries have different origins according to their right and left anatomic locations. On the right, the subclavian artery arises from the innominate artery behind the right sternoclavicular articulation; on the left side, it originates directly from the arch of the aorta. The subclavian artery is divided into three portions. The first portion courses from the origin to the medial border of the scalenus anterior. The second portion lies behind this muscle, and the third portion courses from the lateral border of the scalenus anterior up to the lateral border of the first rib ( Fig. 1 ).

The first portion of the right subclavian artery arises behind the upper part of the right sternoclavicular articulation and passes upward and laterally to the medial margin of the scalenus anterior. It ascends a little above the clavicle, to a varying extent in different cases. It is crossed by the internal jugular and vertebral veins, by the vagus nerve and the cardiac branches of the vagus nerve, and by the subclavian loop of the sympathetic trunk, which forms a ring around the vessel. The anterior jugular vein is directed lateralward in front of the artery but is separated from it by the sternohyoid and sternothyroid strap muscles.

The first portion of the left subclavian artery arises behind the left common carotid and at the level of the fourth thoracic vertebra; it ascends in the superior mediastinum to the root of the neck and then arches lateralward to the medial border of the scalenus anterior. Its anatomic relations are as follows: in front, the vagus, cardiac, and phrenic nerves, which lie parallel with it; the left common carotid artery; left internal jugular and vertebral veins; and the commencement of the left innominate vein. It is covered by the sternothyroid, sternohyoid, and sternocleidomastoid muscles. The second portion of the left subclavian artery lies behind the scalenus anterior. It is very short and forms the highest part of the arch described by the vessel.

On the right side of the neck, the phrenic nerve is separated from the second part of the artery by the scalenus anterior, and on the left side it crosses the first part of the artery close to the medial edge of the muscle. Behind the vessel are the pleura and the scalenus medius; above are the brachial plexus of nerves; below, the pleura. The subclavian vein lies below and in front of the artery, separated from it by the scalenus anterior.

The third portion of the left subclavian artery runs downward and lateralward from the lateral margin of the scalenus anterior to the outer border of the first rib, where it becomes the axillary artery. The external jugular vein crosses its medial part and receives the transverse scapular, transverse cervical, and anterior jugular veins, which frequently form a plexus in front of the artery. Behind the veins, the nerve to the subclavius muscle descends in front of the artery. The terminal part of the artery lies behind the clavicle and the subclavius muscle and is crossed by the transverse scapular vessels. The subclavian vein is in front of and at a slightly lower level than the artery. Behind, it lies on the lowest trunk of the brachial plexus, which intervenes between it and the scalenus medius. Above and to its lateral side are the upper trunks of the brachial plexus and the omohyoid muscle.

The branches of the subclavian artery are the vertebral, internal mammary, thyrocervical, and costocervical trunks. On the left side, all four branches generally arise from the first portion of the vessel; but on the right side, the costocervical trunk usually originates from the second portion of the vessel. On both sides of the neck, the first three branches arise close together at the medial border of the scalenus anterior; in the majority of cases, a free interval of 1.25 to 2.5 cm exists between the commencement of the artery and the origin of the nearest branch.

Incidence

Subclavian vessel injuries account for approximately 5% of all vascular injuries. Busy urban trauma centers report admitting between two and four subclavian vascular injuries per year, although some international trauma centers have reported admitting as many as four patients per month. Subclavian artery injury specifically accounts for 1% to 2% of all acute vascular injuries. Although a majority of these injuries are penetrating, up to 25% are related to blunt mechanism of injury. The low incidence of subclavian artery injury is primarily explained by the anatomic location and the protective barrier provided by the clavicle and thoracic cage. In a study combining both prospective and retrospective reviews, Demetriades et al reported that isolated subclavian vein injuries were present in 44% of the patients, isolated subclavian artery involvement in 39%, and combined injuries in approximately 17% of the cases. On the other hand, Lin et al reported that 24 of 54 patients presenting with subclavian artery injuries also sustained associated venous injuries.

The subclavian vessels are relatively well protected by the overlying clavicle and first rib; however, fractures to these and other adjacent osseous structures may lead to serious life-threatening injury. In one of the largest series published, Natali reported a total of 10 patients with clavicle fracture-induced injury. The incidence of clavicular fractures and associated subclavian vessel injury is estimated to be less than 1%. Richardson et al identified first rib fracture as a useful indicator of severe upper thoracic trauma. In this study, 55 patients with first rib fractures were evaluated, of which 5.5% sustained associated blunt subclavian artery injuries. A comparable review by Phillips demonstrated similar findings in the presence of displaced first rib fractures, with 9% presenting with associated blunt subclavian artery injuries.

The majority of subclavian vessel injuries in the civilian population result from penetrating trauma. Over the past several decades, there has been a steady rise in firearm-related injuries in the United States as a result of increased civilian use of weaponry. Several published series observed a similarly low incidence of blunt versus relatively high incidence of penetrating injury across the globe. Graham’s largest civilian series reported 93 patients sustaining subclavian artery injuries over a 24-year period. Of these, only two resulted from a nonpenetrating injury. Over a period of 10 years, a retrospective review by Lin identified 54 patients with penetrating subclavian artery injuries, of which 85% resulted from gunshot wounds. Conversely, McKinley reported 82% of subclavian artery injuries resulted from stab wounds and 10% from low-velocity gunshot wounds, a trend not appreciated in U.S. regional trauma centers ( Table 2 ).

On the other hand, blunt subclavian artery injuries occur far less frequently. Urban trauma centers report approximately that 1% to 3% of all traumatic subclavian artery injuries result from blunt trauma. The relatively low incidence of blunt vascular trauma is due to the subclavian vessel’s protected anatomic location. Both rapid deceleration injury and bony fractures are responsible for blunt injury of this artery. Not uncommonly, however, the injury remains unrecognized secondary to normal physical examination findings. In other cases, patients experience a delay in symptoms after their initial injury, thereby postponing treatment.