T12 Vertebra

The T12 vertebra is the twelfth and final thoracic vertebra in the spinal column. It serves as a critical transitional vertebra between the thoracic and lumbar regions and exhibits mixed anatomical features of both. T12 plays an important role in supporting the rib cage, transferring spinal loads to the lumbar spine, and anchoring key muscles and ligaments.

Location

T12 is located at the inferior end of the thoracic spine, just superior to the L1 vertebra and inferior to T11. It lies at the level of the twelfth rib and contributes to the posterior boundary of the thoracoabdominal junction.

Structural Characteristics

T12 is a transitional vertebra that has unique hybrid features of both thoracic and lumbar vertebrae:

• Vertebral body: Large and kidney-shaped, similar to lumbar vertebrae
• Vertebral foramen: Smaller and more circular than in upper thoracic levels
• Transverse processes: Do not have costal facets
• Spinous process: Shorter and more horizontal, resembling lumbar vertebrae
• Articular processes: Superior facets are oriented like thoracic vertebrae (posterolateral), while inferior facets are oriented like lumbar vertebrae (lateral and anterior)

Rib Articulation

T12 articulates only with the twelfth rib:

• Costal facet: A single complete facet on each side of the vertebral body for the head of rib 12
• No transverse costal facet: Unlike other thoracic vertebrae, T12 has no facet on its transverse process because rib 12 does not articulate anteriorly

Articulations

• Superior: Articulates with the inferior facets of T11
• Inferior: Articulates with the superior facets of L1
• Rib 12: Articulates with the vertebral body via a costal facet

Function

• Acts as a structural transition between thoracic rigidity and lumbar flexibility
• Supports the last rib and protects upper abdominal organs
• Transfers axial loads to the lumbar spine
• Serves as a key reference level in spinal procedures and imaging

Muscle Attachments

• Psoas major: Originates from the sides of T12 and L1–L5 vertebrae
• Quadratus lumborum: Attaches to the transverse process of T12
• Diaphragm: Crura attach to the anterior surface of T12
• Latissimus dorsi and erector spinae: Attach to the spinous process

Ligament Attachments

• Anterior and posterior longitudinal ligaments
• Ligamentum flavum (between laminae)
• Interspinous and supraspinous ligaments
• Facet joint capsules

Blood Supply

• Arterial: Subcostal arteries (from thoracic aorta)
• Venous: Subcostal veins, draining into the azygos (right) or hemiazygos (left) system

Innervation

• The T12 spinal nerve exits below the T12 vertebra via the T12–L1 intervertebral foramen
• T12 contributes to the subcostal nerve, which innervates portions of the abdominal wall and skin over the hip

Clinical Relevance

• Common fracture site: Due to transition between stiff thoracic and mobile lumbar spine; often injured in trauma or falls
• Compression fractures: Common in osteoporosis; may result in kyphosis or vertebral collapse
• Radiological landmark: Used as a reference point in spinal imaging and anesthesia
• Subcostal nerve entrapment: May cause abdominal wall pain near the iliac crest