Originates at the medial third of the superior nuchal line and occipital protuberance, with attachments arising from the C7–T12 spinous processes

Innervated by the spinal accessory nerve and the ventral rami of C3 and C4

Responsible for elevating, retracting, and depressing the scapula

Arises from the spinous processes of T2–T5 and inserts into the medial surface of the scapula at the root of the spine to the inferior angle

Innervated by the dorsal scapular nerve

Responsible for retracting the scapula and fixing it to the thoracic wall

Arises from the lower portion of the ligamentum nuchae and spinous processes of C7 and T1. Inserts into the medial scapula at the base of the root of the spine of the scapula

Innervated by the dorsal scapular nerve

Responsible for retracting the scapula and fixing it to the thoracic wall

Arise from posterior tubercles of the transverse processes of C1–C4 and inserts at the medial border of the scapula just superior to the rhomboid minor

Innervated by the dorsal scapular nerve and the ventral rami of C3 and C4

Responsible for elevating and rotating the scapula

Arises from the spinous processes of C6–T3 and inserts at the superior border of the second to fourth ribs

Innervated by the second to fifth intercostal nerves

Responsible for elevating the ribs

Arises from the lower half of the ligamentum nuchae and the spinous processes of C7–T3 and inserts at the mastoid process and lateral one third of the superior nuchal line

Innervated by the posterior rami of cervical nerves

Responsible for stabilization and rotation of the skull

Arises from the spinous processes of the T3–T6 and inserts into the posterior tubercles of the transverse processes of C1–C4

Innervated by the posterior rami of cervical nerves

Responsible for stabilization and rotation of the skull

This group can be divided into three main columns: the iliocostalis, longissimus, and spinalis ( Fig. 27-2 ).

A, Dissection demonstrates deep muscle groups of the back. B, Cross-section demonstrates location of the superficial and deep muscle groups.

Each column is divided into cervical, thoracic, and lumbar regions.

The erector spinae share a common aponeurotic band that attaches to the posterior part of iliac crest, the posterior aspect of the sacrum, and the sacroiliac ligaments.

The most lateral column

Originates from the angles of the ribs and inserts in the posterior tubercle of the transverse processes of C4–C6

Innervated by the posterior rami of the spinal nerves

Extends and laterally bends the vertebral column

The intermediate column

Originates from the transverse processes of thoracic vertebrae and inserts on superior transverse processes and articular processes of C2 through C6

Innervated by the posterior rami of the spinal nerves

Extends and laterally bends the vertebral column and extends the neck

The medial column

Originates from thoracic and lumbar spinous processes and inserts on lower cervical spinous processes

Innervated by the posterior rami of the spinal nerves

Extends vertebral column and extends the neck

Made up of three groups of muscles that lie deep to the erector spinae

Originate from transverse processes and insert at the spinous processes of superior vertebrae

Innervated by the posterior rami of the spinal nerves

Stabilizes vertebrae during local movements of the vertebral column

The most superficial group

Divided into three regions: capitis, cervicis, and thoracic

Deep to the semispinalis group

Short triangular bundles

The deepest group

Arise from the transverse process of one vertebra and insert into the root of the spinous process of the next superior vertebra

Anterior to the rib is a layer of retropleural fat and the endothoracic fascia. This layer tracks anteromedially toward the ventral aspect of the vertebral body and may be used as a plane of dissection ( Fig. 27-4 ).

Anatomic illustration after costotransversectomy and retractor placement. Pleura can be separated from the lateral vertebral elements. A layer of retropleural fat is often apparent anteromedially and can aid in establishing the dissection plane.

The aortic arch ascends to the level of T3–T4 and lies anterolaterally to the left side of the vertebral bodies. It may obstruct the view of the vertebral bodies in posterolateral approaches to the vertebral body ( Fig. 27-5 ).

Lateral view of the mediastinum demonstrates the proximity of the aortic arch and esophagus to the vertebral bodies.

Intercostal arteries arise at T3 to T12 from the posterior aorta and travel across the ventral aspect of the vertebral body. The dorsal branch gives rise to the segmental arteries that supply the spinal canal and spinal cord. They then become part of the neurovascular bundle, which runs along the inferior aspect of each rib.

Because the aortic arch does not extend to the most superior aspect of the thoracic cage, it is instead supplied by a branch of the costocervical trunk ( Fig. 27-6 ).

The vascular supply for the first two intercostal spaces is from the costocervical trunk. The first aortic intercostal artery supplies the third interspace.

The esophagus lies ventral to the vertebral body and is pushed slightly to the right side by the descending aorta.

The upper portion of the CTJ contains nerves that form the inferior portion of the brachial plexus.

The C8 nerve and the ventral ramus of the T1 nerve join the brachial plexus. There is also variable involvement of the ventral ramus of T2, which may contribute a small branch to the brachial plexus.

The dorsal ramus of T1 runs along the inferior aspect of the first rib.

Intercostal nerves below T1 may be sacrificed for increased exposure without causing significant neurologic compromise.