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Thoracic spine


Core Procedures

  • Direct posterior exposure

  • Costotransversectomy

  • Transpedicular approach to the thoracic disc space

  • Anterior open transthoracic exposure

  • Endoscopic approach to the thoracic spine

  • Lateral extracavitary approach

  • Trans-sternal approach to the cervicothoracic junction

Surgical surface anatomy

There are limited reliable surface anatomy cues about the thoracic spine. This contributes to the increased risk of performing wrong-level surgery. The spinous process of the first thoracic vertebra can be palpated just distal to the vertebra prominens (C7). It is important to note, however, that there is significant variability as to which spinous process is actually most prominent in this region. With the patient's arms resting at their sides, the scapular spine and inferior angle can be used to approximate the level of the T3 and T7 spinous processes, respectively. Caution should be exercised when referring to such landmarks in the operating room because shoulders are often positioned in abduction, in forward flexion or under traction. Anteriorly, the T2–3 level can often be inferred by the suprasternal notch and the T4–5 level can be inferred by the sternal angle.

Clinical anatomy

Muscles

Posteriorly, the superficial layer of muscle consists of latissimus dorsi and trapezius. The intermediate layer consists of levator scapulae, rhomboids major and minor, and serratus posterior. The deep layer is made up of erector spinae (iliocostalis, longissimus and spinalis from lateral to medial) and the transversospinalis group (semispinalis thoracis, multifidus and rotatores brevis and longus from superficial to deep).

Vascular supply

The aortic arch typically reaches the T4 level. As it descends, the aorta moves from being left-sided to more anterior beyond the T7 level. More distally, it courses along the left side of the thoracic vertebrae. The three major branches originating from the top of the arch are the brachiocephalic trunk, left common carotid artery and left subclavian artery. The segmental branches coming off the aorta run along the waist of the vertebral body, deep to the azygos or hemiazygos vein, thoracic duct and sympathetic trunk; they divide into the intercostal arteries and radiculomedullary branches that feed the paraspinal muscles.

The vertebral venous plexus (VVP) is a complex network of vessels distributed along the anterior body and posterior elements of the spine, as well as circumferentially around the thecal sac within the spinal canal. By virtue of being uniquely valveless, the veins of the VVP accommodate bidirectional flow. The plexus maintains continuity with the cerebral sinuses proximally and the sacral plexus distally. In men, the prostate venous plexus also directly communicates with the VVP. This relationship has been used to explain the heightened predisposition towards spinal metastases in the setting of prostate cancer. During surgery, air or even other materials like cement can inadvertently enter an injured venous plexus and embolize to the brain. The epidural veins transmit pressure to the thecal sac when using Valsalva manœuvres intraoperatively to check for cerebrospinal fluid (CSF) leaks. Distally, the VVP drains into the azygos vein on the right side of the thoracic spine and into the hemiazygos vein on the left side. Both the hemi­azygos and azygos veins communicate with each other at multiple levels.

Bones and joints: costovertebral anatomy

The head of a rib articulates with a vertebral body via costovertebral and costotransverse synovial joints; there are multiple costovertebral and costotransverse ligaments. The superior costotransverse ligament forms a tunnel with the spine through which the dorsal ramus of the spinal nerve and the dorsal branch of the intercostal artery pass. Within the intercostal neurovascular bundle, the vein is typically cephalad to the artery, which is cephalad to the nerve.

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