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http://upload.orthobullets.com/topic/2069/images/osteology 2.jpg
http://upload.orthobullets.com/topic/2069/images/atlas ossification.jpg
http://upload.orthobullets.com/topic/2069/images/c2 ossification better.jpg
http://upload.orthobullets.com/topic/2069/images/ossification center c2_moved.jpg
http://upload.orthobullets.com/topic/2069/images/basilar_moved.jpg
http://upload.orthobullets.com/topic/2069/images/cervical kinematics_moved.jpg
Embryology
  • Genetics
    • homeobox, or Hox genes direct and regulate processes of embryonic differentiation and segmentation along craniocaudal axis
    • see each segment for embryologic development
Osteology
  • The cervical spine contains 7 vertebral bodies
    • C1 (atlas)
    • C2 (axis)
    • C1 to C7
      • have a transverse foramen
      • vertebral artery travels through transverse foramen of C1 to C6
    • C2 to C6
      • have bifid spinous process
    • C7
      • despite having a transverse foramen, the vertebral artery does NOT travel through it in the majority of individuals
      • there is no C8 vertebral body although there is a C8 nerve root
Alignment
  • Normal sagittal lordosis (measured from C2 to C7)
Spinal Canal
  • Spinal canal
    • normal diameter is 17mm
      • <13mm indicates possible cord compression
Atlas (C1)
  • Has no vertebral body and no spinous process
  • Embryology
    • three ossification centers
      • one for each lateral mass
        • lateral masses fuse to body at age 7
      • one for vertebral body
        • vertebral body does not appear until 1 year of age
  • Articulations
    • occiput-C1
      • two superior concave facets that articulate with the occipital condyles
      • makes up 50% of neck flexion and extension
    • C1-C2 (see below)
Axis (C2)
  •  Axis Osteology
    • axis has odontoid process (dens) and body
    • embryology
      • develops from five ossification centers  
      • subdental (basilar) synchondrosis is an initial cartilagenous junction between the dens and vertebral body that does not fuse until ~6 years of age  
      • the secondary ossification center appears at ~ age 3 and fuses to the dens at ~ age 12 
  • Axis Kinetmatics
    • CI-C2 (atlantoaxial) articulation
      • is a diarthrodal joint that provides 
        • 50 (of 100) degrees of cervical rotation 
        • 10 (of 110) degrees of flexion/extension 
        • 0 (of 68) degrees of lateral bend 
    • C2-3 joint
      • participates is subaxial (C2-C7) cervical motion which provides
        • 50 degrees of flexion/extension of cervical spine
        • 50 degrees of rotation of cervical spine
        • 60 degreesof lateral bend
  • C2 Blood Supply
    • a vascular watershed exists between the apex and the base of the odontoid   
      • apex is supplied by branches of internal carorid artery
      • base is supplied from branches of vertebral artery
      • the limited blood supply in this watershed area is thought to affect healing of type II odontoid fractures.
Occipital-C1-C2 Ligamentous Complex
  •  Provided by the odontoid process and its supporting ligaments
    • transverse ligament 
      • limits anterior translation of the atlas
    • apical ligaments
      •  limit rotation of the upper cervical spine
    • alar ligaments
      • limit rotation of the upper cervical spine
Subaxial Cervical Spine (C3 to C7)
  • C1 to C7
    • have a transverse foramen
    • vertebral artery travels through transverse foramen of C1 to C6
  • C2 to C6
    • have bifid spinous process
  • C6
    • contains palpable carotid tubercle which is a valuble landmark for anterior approach to cervical spine
  • C7
    • nonbifid spinous process
    • despite having a transverse foramen, the vertebral artery does NOT travel through it in the majority of patients
    • there is no C8 vertebral body although there is a C8 nerve root
  • The superior articular facets of the subaxial cervical spine (C3-C7) are oriented in a posteromedial direction at C3 and posterolateral direction at C7, with a variable transition between these levels  
 

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