Updated: 6/22/2021

Thoracic Spine Anatomy

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https://upload.orthobullets.com/topic/2070/images/pedicle diameter illustration 3.jpg
https://upload.orthobullets.com/topic/2070/images/kim_2.jpg
https://upload.orthobullets.com/topic/2070/images/thoracic vert.jpg
https://upload.orthobullets.com/topic/2070/images/endplate area.jpg
https://upload.orthobullets.com/topic/2070/images/spinal canal diameter.jpg
https://upload.orthobullets.com/topic/2070/images/cervical facets.jpg
https://upload.orthobullets.com/topic/2070/images/rom.jpg
  • Alignment
    • Sagittal plane alignment
      • normal thoracic kyphosis
        • averages 35° degrees
          • normal range is 20° to 50°
  • Osteology
    • Vertebral prominens
      • the long prominent spinous process found at C7
    • Costal facets
      • articulation between ribs and vertebral segments
      • present on all vertebral bodies and transverse processes from T1 to T9
      • articulation with ribs leads to increased rigidity of thoracic spine (most rigid in axial skeleton)
    • Vertebral body size
      • increases progressively from T1 to T12
    • Spinal canal dimensions
      • varies from T1 to T12
  • Motion
    • The orientation of the facets (zygapophyseal) joints determines the degree and plane of motion at that level
      • varies throughout the spine to meet physiologic function
      • cervical spine (C3-7)
        • planes
          • 0° coronal
          • 45° sagittal (angled superio-medially)
        • function
          • allows flexion-extension, lateral flexion, rotation
      • thoracic spine
        • planes
          • 20° coronal
          • 55° sagittal (facets in coronal plane)
          • 6 degrees of freedom
        • function
          • allows some rotation, minimal flexion-extension (also limited by ribs)
          • prevents downward flexion on heart and lungs
      • lumbar spine
        • plane
          • 50° coronal
          • 90° sagittal (facets in sagittal plane)
        • function
          • allows flexion-extension, minimal rotation
          • helps increase abdominal pressure
  • Thoracic Pedicle Anatomy
    • Pedicle diameter
      • the pedicle wall is twice as thick medially as laterally
      • T4 has the narrowest pedicle diameter (on average)
      • T7 can be irregular and have a narrow diameter on the concave side in AIS
      • T12 usually has larger pedicle diameter than L1
    • Pedicle length
      • pedicle length decreases from T1 to T4 and then increases again as you move distal in the thoracic spine
        • T1: 20mm
        • T4: 14mm (shortest pedicle)
        • T10: 20 mm
    • Pedicle angle
      • transverse pedicle angle
        • varies from 10deg (mid thoracic spine) to 30deg (L5)
      • sagittal pedicle angle
        • 15-17deg cephalad for majority of thoracic spine
        • neutral (0deg) for lumbar spine except L5 (caudal)
  • Erector Spinae Muscles
    • Characteristics
      • functions to extend the trunk
      • located dorsal to vertebral column
      • innervated by dorsal rami of spinal nerves
    • Erector spinae muscles include
      • spinalis
        • most medial
        • origin and insertion: spinous process to spinous process
      • longissimus
        • intermediate
        • origin and insertion: transverse process to transverse process
      • iliocostalis
        • most lateral
        • origin: ilium and ribs
        • insertion: ribs and transverse process
  • Surgical Approaches
    • Surgical approaches for thoracic disc herniation
      • laminectomy/hemilaminectomy
      • transpedicular
      • costotransversectomy
      • lateral extracavitary
      • anterior intracavitary
        • thoracotomy
        • VATS (video assisted thoracoscopic surgery)

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(OBQ08.190) In the adult spine, which of the following pedicles have the smallest average transverse diameter.

QID: 576

T1

20%

(794/4032)

T6

69%

(2763/4032)

T12

9%

(377/4032)

L3

1%

(53/4032)

L5

1%

(37/4032)

L 3 C

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