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Thoracic Spine Anatomy

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Topic updated on 01/03/14 5:11pm
Alignment
Osteology
  • Vertebral prominens
    • the long prominent spinous process found at T1
  • 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. Topic Review Topic

1. T1
2. T6
3. T12
4. L3
5. L5

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