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)