Thoracic Vertebrae (T1–T12)¶
Definition¶
The thoracic spine consists of 12 vertebrae (T1–T12) situated between the cervical and lumbar regions. It forms the posterior wall of the thoracic cage and articulates with the 12 pairs of ribs. The thoracic spine is the least mobile segment of the vertebral column due to the stabilizing effect of the rib cage and the orientation of the facet joints.
Anatomy¶
General Features¶
Thoracic vertebrae are characterized by several distinguishing features:
- Heart-shaped vertebral bodies — intermediate in size between cervical and lumbar, increasing progressively from T1 to T12
- Costal facets — articular surfaces on the vertebral bodies and transverse processes for rib articulation
- Superior and inferior costal demifacets — on the posterolateral vertebral body, forming the costovertebral joints
- Transverse costal facets — on the anterior surface of the transverse processes (T1–T10), forming the costotransverse joints
- Long, inferiorly angled spinous processes — overlap the vertebra below, particularly in the mid-thoracic region (T5–T8)
- Circular vertebral foramen — smaller than cervical or lumbar, as the thoracic cord is narrower
- Coronal-oriented facet joints — approximately 60° to the axial plane, limiting flexion/extension but permitting rotation
Regional Variations¶
| Region | Characteristics |
|---|---|
| T1–T4 | Transitional with cervical features; smaller bodies; more horizontal spinous processes |
| T5–T8 | "Typical" thoracic morphology; most steeply angled spinous processes |
| T9–T12 | Transitional with lumbar features; larger bodies; T11–T12 lack transverse costal facets (floating ribs) |
Clinical Pearl
The thoracic spine is the most common location for osteoporotic compression fractures, particularly at the thoracolumbar junction (T11–L1). The normal thoracic kyphosis creates a biomechanical disadvantage with increased anterior loading on vertebral bodies.
Rib Articulations¶
Each typical rib articulates with the thoracic spine at two points:
- Costovertebral joint — the rib head articulates with the superior costal facet of its own vertebra and the inferior costal demifacet of the vertebra above
- Costotransverse joint — the rib tubercle articulates with the transverse costal facet
These dual articulations provide significant stability but limit motion, making the thoracic spine the most rigid segment.
Imaging Findings¶
Radiography¶
- AP view — evaluates vertebral body alignment, pedicle integrity, disc spaces, and scoliosis
- Lateral view — assesses vertebral body heights (anterior vs. posterior), kyphosis, disc spaces, and compression fractures
Normal Thoracic Kyphosis
Normal thoracic kyphosis measures approximately 20°–45° (Cobb angle, T2–T12). Values exceeding 45° may indicate Scheuermann disease, osteoporotic wedging, or post-traumatic deformity.
CT¶
CT is valuable for:
- Detailed fracture characterization, particularly burst fractures
- Evaluation of the posterior elements (pedicles, laminae, facets)
- Assessment of retropulsed bone fragments in the spinal canal
- Rib and costovertebral joint pathology
MRI¶
| Finding | T1 Signal | T2 Signal | Significance |
|---|---|---|---|
| Normal marrow | Bright (fatty) | Intermediate | Age-dependent marrow conversion |
| Acute compression fracture | Low | High/heterogeneous | Edema indicates acuity |
| Chronic compression fracture | Isointense to marrow | Isointense | No edema; may have cleft sign |
| Scheuermann changes | — | — | Irregular endplates, Schmorl nodes, wedging |
Key Points¶
- The thoracic spine (T1–T12) is stabilized by rib articulations, making it the least mobile segment
- Costal facets on the bodies and transverse processes are unique to thoracic vertebrae
- Facet joints are coronally oriented (~60°), favoring rotation over flexion/extension
- The thoracolumbar junction (T11–L1) is a biomechanical transition zone vulnerable to fractures
- Normal thoracic kyphosis is 20°–45°
References¶
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Waxenbaum JA, Reddy V, Margetis K. Anatomy, Back, Thoracic Vertebrae. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026. PMID: 29083651. https://www.ncbi.nlm.nih.gov/books/NBK459153/
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Beyer B, Biteau D, Snoeck O, Dugailly PM, Bastir M, Feipel V. Morphometric analysis of the costal facet of the thoracic vertebrae. Anat Sci Int. 2020;95(4):457-465. PMID: 32335803. https://pubmed.ncbi.nlm.nih.gov/32335803/
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Saker E, Graham RA, Nicholas R, D'Antoni AV, Loukas M, Oskouian RJ, Tubbs RS. Ligaments of the Costovertebral Joints including Biomechanics, Innervations, and Clinical Applications: A Comprehensive Review with Application to Approaches to the Thoracic Spine. Cureus. 2016;8(11):e874. PMID: 27994992. https://pmc.ncbi.nlm.nih.gov/articles/PMC5154401/
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Duprey S, Subit D, Guillemot H, Kent RW. Biomechanical properties of the costovertebral joint. Med Eng Phys. 2010;32(2):222-227. PMID: 20036178. https://pubmed.ncbi.nlm.nih.gov/20036178/
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Fon GT, Pitt MJ, Thies AC Jr. Thoracic kyphosis: range in normal subjects. AJR Am J Roentgenol. 1980;134(5):979-983. PMID: 6768276. https://pubmed.ncbi.nlm.nih.gov/6768276/
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Fradet L, Petit Y, Wagnac E, Aubin CE, Arnoux PJ. Biomechanics of thoracolumbar junction vertebral fractures from various kinematic conditions. Med Biol Eng Comput. 2014;52(1):87-94. PMID: 24165806. https://pubmed.ncbi.nlm.nih.gov/24165806/