Anatomy of the Thoracic Outlet

The Washington University Center for Thoracic Outlet Syndrome at Barnes-Jewish Hospital promotes understanding of the basic anatomy of the thoracic outlet among patients. This helps them comprehend how the compression of nerves, arteries, veins, and blood vessels in this area affects an individual’s health and well-being and can lead to TOS.

The thoracic outlet region is located within the lower part of the neck, beginning just above and behind the clavicle and extending to the upper part of the arm. Using surface landmarks, the thoracic outlet is located next to the large muscle that runs vertically in the neck, called the sternocleidomastoid muscle, and in front of the muscle that runs across the back of the neck, called the trapezius muscle. The lower part of the thoracic outlet extends behind the clavicle, underneath the pectoralis muscles, and in front of the shoulder.