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Applied surgical anatomy of the craniovertebral spine

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This presentation was made at the Advanced Cervical Spine Course conducted by Dr. Sandeep Sonone and Dr. Kshitij Chaudhary for the Bombay Orthopaedic Society. http://bombayorth.org/academics/instructional-courses/

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Applied surgical anatomy of the craniovertebral spine

  1. 1. Dr. Kshitij Chaudhary, MS, DNB, FACS Consultant Spine Surgeon Adult and Pediatric Spine Surgert Sir HN Reliance Foundation Hospital Mumbai @kcspine (Twitter) S U R G I C A L A N A T O M Y O F T H E P O S T E R I O R A P P R O A C H T O C V J
  2. 2. Bones Articulations Alignment Load transmission
  3. 3. B O N E S
  4. 4. External occipital protuberance (star) Superior nuchal line (upper dotted line) Inferior nuchal line (lower dotted line) Medial nuchal line (vertical blank dotted line)
  5. 5. Reference The EOP corresponds to the torcula (or confluence of sinus) The superior nuchal line → transverse sinus) Medial nuchal line → occipital keel. Thickest and densest at the EOP - really have to drill and tap both cortices for the occipital screws. The thickness reduces as you travel inferiorly and laterally. Inverted triangle with the base on the EOP. Midline screws are going to be typically 10-12 mm Note: the diagram has a occipitalised atlas , same patients intraoperative photos are shown
  6. 6. C1 - Atlas
  7. 7. C1 - Vertebral Artery V3 12 mm
  8. 8. The location of the VA and C2 ganglion in relation to the C1 posterior a Note - those blue areas on this cadaveric specimen are large venous si
  9. 9. a) Conventional entry point. b) Posterior arch screw c) Notch technique
  10. 10. Direct the screw just below the midpoint of the anterior arch. Between Lower 20-40%, (Jin Sup Yeom, Riew) With 0 to 15 degree medial angulation such direction has the least chance of entering the OC joint. The overhang on the posterior C1 arch sometimes gets in the way and pushes the trajectory upwards. Remember what you see on the lateral X-ray is a two D projection of the lateral mass. The superior facet of the C1 lateral mass is deeply concave and will be violated by this trajectory
  11. 11. Ant. relation of C1 lateral mass Hypoglossal N. Internal Carotid
  12. 12. Ponticulus posticus Young et al. JBJS Am 2005 15%
  13. 13. Young et al. JBJS Am 2005
  14. 14. Elliott, World Neurosurg 2014
  15. 15. Lee, J Clin Neurosci, 2013 Young et al. JBJS Am 2005
  16. 16. C2 - Axis
  17. 17. Superior Articular Facet C2 Closer to Body than the Lamina
  18. 18. Pedicle and Pars C2 Pedicle Pars
  19. 19. Superior Articular Facet C2 Vertebral artery makes a deep groove
  20. 20. Course of Vertebral Artery V1 V2 V3 zones
  21. 21. Vertebral Artery Cave Tubbs, World Neurosurg, 2016 High Riding VA V1 Zone Another common anomaly is a high riding VA in the vertebral artery cave underneath the C2 superior facet. Sometimes the VA bends too far high under the sup facet, too posterior near the dorsal cortex of isthmus, and too medial near the C2 body and - High Riding VA
  22. 22. High riding vertebral artery
  23. 23. Internal height Isthmus height
  24. 24. Internal height < 2mm TOO HIGH
  25. 25. Internal height < 2mm Isthmus height < 5mm 1 in 5 times TAS is not safe Bloch et al, JNS Spine, 2001 TOO POSTERIOR
  26. 26. Variations in size of Pars High riding Vertebral Artery Learn how to manipulate DICOM images yourself! Using either Osirix or Horos or a similar software.
  27. 27. Cacciola et al., Neuro India, 2004 TOO MEDIAL
  28. 28. Reference C2 pedicle screw (solid black line) C2 Pars screw (dotted line)
  29. 29. Reference
  30. 30. Course of Vertebral Artery V1 V2 V3 zones
  31. 31. Anomalous course of VA Variations are Enormous
  32. 32. Anomalous course Persistent first intersegmental a. Fenestrated VA Anomalous origin of PICA Anomalies in Occipitalized atlas
  33. 33. Persistent First Intersegmental A. Hong et al. JNS, 2008 5-8% Yamazaki, Spine, 2012
  34. 34. Fenestrated VA Hong et al. JNS, 2008 1-2% Yamazaki, Spine, 2012
  35. 35. Anomalous origin of PICA Hong et al. JNS 2008 Sometimes the origin of the PICA is anomalous and is below the C1 posterior arch. Injury to this vessel can cause a cerebellar infract.
  36. 36. Anomalous with occipitalized C1 Type 1 - VA enters below the posterior arch but is not in front of the occipitalised LM Type 2 - VA enters below the posterior arch of C1 but is in front of LM of C1 Type 3 - VA enters above the posterior arch, enters an osseous foramen created between C1 and Occiput Type 4 - VA is absent
  37. 37. Yamazaki, Spine, 2012
  38. 38. Neo et al., Spine, 2008 Hong et al. JNS 2008
  39. 39. Choose wisely! TAS C2 pedicle C2 laminar Yanni et al. Neurosurgery 2010 Pars Risky Safer
  40. 40. A R T I C U L A T I O N S
  41. 41. 6 degrees of freedom that are normal wo additional degrees of freedom are pathological 1) Vertical settling (Basilar invagination) 2) Distraction (atlanto-occipital dislocation)
  42. 42. Cradle Pivot Root Column From White and Punjabi Textbook of Biomechanics
  43. 43. Atlas (Cradle) Shallow Deep Occipito-atlantal joint Atlas serves to cradle the occiput, superior facet receive the condyles of the occiput Ball and socket configuration. Highly conformal nature - stability is stems primarily from the depth of this socket. Rigid capsule and strong ligaments - instability therefore uncommon. At least in adults. (in children and some clinical conditions like Downs it may be a bit unstable inherently due to lax ligaments).
  44. 44. Atlas (Cradle) Slide and roll (condylar joint) The only physiological motion possible here is Flexion extension motion, i.e. nodding, is about 25º - out of which extension is the majority component. The movement is typical of a condylar joint which is “slide and roll” Lateral bending and rotations are limited and are not physiological movements can cannot be produced in isolation by action of muscles alone.
  45. 45. Atlas (Cradle) 0 7.5 15 22.5 Flexion Extension Lateral bending Axial rotation 21º Elastic zone Lateral bending and rotations are limited and are not physiological movements can cannot be produced in isolation by action of muscles alone. Note that significantly large portion of the extension ROM is in the elastic zone indicating that OC joint has significant inherent stability.
  46. 46. Atlas (Cradle) Because it is very stable, injuries like this are quite uncommon. They are more common in children due to laxity of ligaments
  47. 47. Atlas (Cradle) Indirect Sensitivity 38% False positive 10% Sensitivity 31% False positive 50% Sensitivity 50% False positive 30% X-rays Direct Condylar-C1 Interval 100% specific 100% Sensitive CT scan Pang et al. Neurosurg 2007
  48. 48. Atlas (Cradle) >4 mm distraction Asymmetrical joints Ruptured alar, tectorial membrane CCI
  49. 49. Axis (Pivot) Biconvex configuration Held by loose capsule - designed to permit large ROM – therefore the capsule and the bone contributes little to the joint stability.
  50. 50. Axis (Pivot) Major stability is thus provided by Dens in the osseoligamentous ring – the pivot joint. Virtually all other ligaments play a secondary role.
  51. 51. Center of gravity of the head is 2 cm anterior to the occipital condyles
  52. 52. TAL and Alar ligaments F TAL – restricts forward translation Alar ligament restricts rotations
  53. 53. Axis (Pivot)
  54. 54. Atlanto-axial joint (C1-C2) 0 10 20 30 40 Flexion Extension Lateral bending Axial rotation Neutral zone About 56% of total cervical spine rotation and 90% of overall CVJ rotation occurs at C1-C2. The average motion on either side is about 38.9. Note that this motion has a substantial neutral zone component This suggests that the capsules holding the C1- C2 articulations are relatively lax and muscular action is primarily responsible for maintaining rotational stability.
  55. 55. Axis (Pivot) Washer Few muscles act directly on the atlas. The movement of atlas is thus passive, governed by the muscles that act on the head. The atlas thus acts as a passive washer.
  56. 56. The concept of centrode and Instantaneous axis of rotation.
  57. 57. Centrode is the collection of IAR (instantaneous axis of rotation) In a patient with a odontoidectomy, the centrode is over a large area making the C1-C2 joint unstable and wobbly.
  58. 58. The Root C2-C3 Pillar view C2-3 facet joints inclined medially cradling the posterior elements And the c2 body dips down into the vertebral column like a root.
  59. 59. The Root C2-C3 Superior and inferior facet of C2 are not above each other unlike subaxial cerivcal spine
  60. 60. C2-3 Load transmission Stress area
  61. 61. C2-3 Type 1 Type 2 Type 3 Hangman’s fractures
  62. 62. A L I G N M E N T
  63. 63. Cervical lordosis Lordosis in asymptomatic adults Most of the cervical lordosis is in the C1-C2 region.
  64. 64. Try not to fix the C1C2 in kyphosis. Remember that the lordosis in the cervical spine – 80% is at the C1-C2. IF C1-C2 is fixed in kyphosis the subaxial cervical spine changes and depending on the severity of the kyphosis a swan neck deformity develops.
  65. 65. CMA => 135º Cervicomedullary angle should be restored to 135 degree or more.
  66. 66. pBC2 < 9 mm Basion to posterior inferior corner of the C2. Asses how much odontoid is behind this line. You want it less than 9 mm.
  67. 67. Above McRae line Vertical settling (BI)
  68. 68. 45 deg 22 mm Occipito cervical relationship If OC fixation is in kyphosis, patient will find it difficult to swallow, dysphagia, and is predisposed to adjacent segment problems.
  69. 69. We use 3D printed Real-size anatomical models of complex CVJ pathology before surgery to understand pathoanatomy Thank you @kcspine https://spine101.wordpress.com

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