Skip to Main Content

++

Thoracic outlet syndrome (TOS), a term coined by Rob and Standeven,1 refers to compression of the subclavian vessels and brachial plexus at the superior aperture of the chest. It was previously designated as scalenus anticus, costoclavicular, hyperabduction, cervical rib, and first thoracic rib syndromes according to presumed etiologies. The various syndromes are similar, and the compression mechanism is often difficult to identify. Most compressive factors operate against the first rib.2,3

++

At the superior aperture of the thorax, the subclavian vessels and the brachial plexus traverse the cervicoaxillary canal to reach the upper extremity. The cervicoaxillary canal is divided into two sections by the first rib: the proximal division, composed of the scalene triangle and the costoclavicular space, and the distal division, composed of the axilla (Fig. 124-1). The proximal division is important to achieve acceptable neurovascular decompression. It is bounded superiorly by the clavicle, inferiorly by the first rib, anteromedially by the costoclavicular ligament, and posterolaterally by the scalenus medius (middle scalene) muscle and the long thoracic nerve. The scalenus anticus (anterior scalene) muscle, which inserts on the scalene tubercle of the first rib, divides the costoclavicular space into two compartments: The anteromedial compartment contains the subclavian vein, and the posterolateral compartment contains the subclavian artery and the brachial plexus. The latter compartment, which is bounded by the scalenus anticus (anterior scalene) muscle anteriorly, the scalenus medius (middle scalene) muscle posteriorly, and the first rib inferiorly, is called the scalene triangle.

++
Figure 124-1.
Graphic Jump Location

The cervicoaxillary canal has a proximal division consisting of the scalene triangle and costoclavicular space and a distal division composed of the axilla. The proximal division is more susceptible to neurovascular compression.

++

The cervicoaxillary canal, particularly its proximal division, also termed the costoclavicular area, normally has ample space for the passage of the neurovascular bundle without compression. Narrowing of this space occurs during functional maneuvers. It narrows during abduction of the arm because the clavicle rotates backward toward the first rib and the insertion of the scalenus anticus (anterior scalene) muscle. In hyperabduction, the neurovascular bundle is pulled around the pectoralis minor tendon, the coracoid process, and the head of the humerus. During this maneuver, the coracoid process tilts downward and thus exaggerates the tension on the bundle. The sternoclavicular joint, which ordinarily forms an angle of 15–20 degrees, forms a smaller angle when the outer end of the clavicle descends (as in drooping of the shoulders in poor posture), and narrowing of the costoclavicular space may occur. Normally, during inspiration, the scalenus anticus muscle raises the first rib and thus narrows the costoclavicular space. This muscle may cause an abnormal lift of the first rib, as in cases of severe emphysema or excessive muscular development, which is seen in young adults.

++

The scalene triangle, which normally occurs between the scalenus anticus anteriorly, ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessSurgery Full Site: One-Year Subscription

Connect to the full suite of AccessSurgery content and resources including more than 160 instructional videos, 16,000+ high-quality images, interactive board review, 20+ textbooks, and more.

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessSurgery

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.