Surgical Approach: Fixation at C1-2

1. Surgical Approach: Fixation at C1-2 • Kamal R.M. Woods, MD • Department of Neurological Surgery • Loma Linda University Medical Center

2. Surgical Management of Odontoid Fractures • Kamal R.M. Woods, MD • Department of Neurological Surgery • Loma Linda University Medical Center

3. Outline • Anatomy of upper cervical spine • Types of odontoid fractures • Mechanism of injury • Non-surgical management • Surgical approaches • Case Presentation • Summary

7. Ligaments at C1-2 • 1/3 cord • 1/3 dens • 1/3 empty Spinal Canal http://www.pt.ntu.edu.tw/hmchai/Kines04/KINspine/Spine.files/AAAjointSup.jpg

8. Vertebral Artery • Arises from subclavian artery • Enters foramen transversarium at C6 • Turns laterally at C2 • Exits foramina transversarium at C1 • Travels posteriorly at C1 (vertebral groove) • Ascends superiorly along clivus http://www.nass.co.uk

9. FRACTURE FEATURE Type I Small oblique avulsion of upper 1/3 of odontoid Type II Fracture at junction of dens and C2 Type IIa Comminuted fracture at base of odontoid Type III Fx through body of C2, incl one or both sup articular processes Types of Odontoid Fractures • Anderson and D’Alonzo classification (1974):

10. Types of C2 Fractures http://www.nypemergency.org

11. Hangman Fractures http://www.nypemergency.org

12. Jefferson Fractures • Unilateral/bilateral • Ant + Post arch of C1 • Axial loading to head(ex: diving) http://uuhsc.utah.edu/rad/medstud/NeuroCaseStudies/Images/Neuro%20Case%2015%20jefferson%20fracture.jpg

13. Mechanisms of Injury for Odontoid Fractures • Flexion vs extension loading • Flex loading anterior displacement of dens (more common; ex: MVC) • Ext loading posterior displacement of dens (ex: fall on forehead)

14. Type I Odontoid Fractures • Upper 1/3 of dens • Avulsion of alar ligament • < 1% of odontoid fractures • Usually stable b/c transverse ligament intact • Associated with AOD- unstable

15. Type 1 Odontoid Fracture

16. Type II Odontoid Fractures • Neck of dens • Most common odontoid fracture • Subtype IIa (comminuted) highly unstable • Treatment controversial: external vs internal fixation

17. Type II Odontoid Fracture

18. Type II Odontoid Fracture

19. Type IIIOdontoid Fractures • Involve body and possibly superior facet of C2 • Usually stable • Unstable if transverse ligament disrupted • Green: n=75; 69 conservative, 1 non-union

20. Type III Odontoid Fracture

21. Algorithm for Treatment of Odontoid Fractures Odontoid Fractures Type I Type II Type III No AOD AOD ??? MRI TL intact TL disrupted Collar Surgery Brace/halo Posterior Fusion Fails Comminuted Simple fx Post fusion Ant vs post fus

22. Type II Odontoid Fxs: Non-surgical Management • Collar vs Brace vs Halo • 75% upper cervical motion restriction w/ halo • 45% restriction w/ conventional braces (ex: Minerva) • Disadvantages of halo: precludes working, pin-site infection, skin break-down, skull perforation • After several months of immobilization, significant number of patients still need surgery • 27-75% non-union rate with external fixation

23. AUTHOR AND YEAR NO. OF PATIENTS NONUNION RATE (%) SIGNIFICANT FACTORS Anderson & D'Alonzo, 19747 49 36 None specified Apuzzo et al, 197826 45 33 Age >40 yr, displacement >4 mm Ekong et al, 198110 17 41 Age ≥55 yr, displacement >4-6 mm Hadley et al, 198512 40 26 Not age, displacement >6 mm Clark & White, 19858 106 32 Not age, displacement >5 mm Dunn & Seljeskog, 19869 88 24 Age >65 yr, posterior displacement Hanssen & Cabanela, 198777 42 50 Age >72 yr, posterior displacement Schweigel, 198733 47 10 Not age, not displacement Hadley et al, 19892 65 28 Not age, displacement ≥6 mm Ryan & Taylor, 199378 35 77 Posterior displacement Seybold & Bayley, 199834 37 29 Not age, displacement unknown Greene et al, 199735 88 28 Displacement ≥6 mm Non-union of Type II Odontoid Fractures Treated Conservatively

24. Type II Odontoid Fxs: Indications for Surgery • Fracture cannot be maintain by external orthosis (serial xrays) • Rupture of transverse ligament • 5mm or more displacement of dens • Comminuted fracture of dens (type IIa) • (Older patients)

25. Surgical Approaches to C1-2 fusion • Posterior bone and wire fusion • Posterior transarticular screw fixation • Anterior transfacetal screw fixation • Posterior fusion with lateral mass screws/rods • Posterior fusion with pedicle screws/rods • Posterior fusion with translaminar screws/rods • Anterior odontoid screw fixation

26. Anterior vs Posterior Approach • 50% cervical rotatory excursion at C1-2 • Posterior fusion eliminates atlantoaxial rotation, usually noticeable by patient • Odontoid screw fixation: provides immediate stabilization, promotes bone healing, preserves C1-2 rotation • Initial anterior approach morbid due to extensive neck dissection

27. Posterior C1-2 Approaches • Initial exposure same for all posterior fusions • Midline incision • Avascular plane • Bipolar dissection/blunt dissection (cobb and gauze) • May extend superiorly to ext occipital protuberance • Lateral dissection limited by vertebral arteries

28. Posterior C1-2 Bone and Wire Fusion • Traditional approach to C1-2 fusion • Traynelis (1997): 64% fusion, 2% morbidity/mortality • Occiput-C2 (vs C1-2) if gross O-A instabilty or poor integrity of post C1 arch

29. Posterior Bone and Wire Fusion • Interspinous • Facet/Transarticluar • Interlaminar/Sublaminar (Halifax clamp) Methods of C1-2 Wiring

30. Interspinous Wiring

31. Facet/Transarticular Wiring

32. Interlaminar Wiring

33. Bone Graft • Autograft vs allograft • Tricortical iliac crest graft wedge (gold standard)

34. Posterior Fusion with C1-2 Transarticular Screw Fixation • Unilateral/Bilateral • 3.5mm screw through the C2 pedicle, across the C1-2 facet, and into each lateral mass of C1 • C1 and 2 become rigidly coupled • Articular surfaces of C1 and 2 are prepared to acheive fusion across the facet joint • Interspinous wiring? Halo immobilization?

35. Posterior C1-2 Fusion with Lateral Mass Screws • Harm’s procedure • Useful when posterior elements absent or disrupted • Superior rotational stability at facets vs wiring (biomechanical) • Immediate rigidity -better fusion -no halo

36. Posterior C1-2 Fusion with Lateral Mass Screws • Roy-Camille • Variations in entry point, trajectory • An technique lowest risk of nerve root injury • screw </=15mm

37. Posterior C1-2 Fusion with Pedicle Screws • 3 column fixation (A) • Superior to lateral mass screws (biomechanical) • Preop CT: bones, verts, nn. • Enter lateral to center of facet, close to post margin of superior articular surface • Point of entry decorticated with high speed drill • Angles vary (B, C)

38. Posterior C1-2 Fusion with Translaminar Screws • First presented in 2003 at Cervical Spine Research Society • Technique published in 2004 • Minimize injury to vertebral artery as seen with transarticular and pedicle screws • Crossing, bilateral translaminar screws

39. Anterior Odontoid Screw Fixation • Most type II, some type III • Does not require intact posterior elements • Acute fractures (6 months or less), not os odontoideum* • Intact transverse ligament (absolute)* • No oblique and anterior slope (relative)* • No severe osteopenia (relative)* * Posterior fusion Apfelbaum RI: Anterior Screw Fixation of Odontoid Fractures (Aesculap Scientific Info 24). Tuttlingen, Germany, Aesculap AG, 1992. 51a. Apfelbaum RI, Lonser RR, Veres R, et al: Direct anterior screw fixation for recent and remote odontoid fractures. J Neurosurg 93(2Supp):227-236.

40. Anterior Odontoid Screw: Surgical Approach • Prone • Shoulder roll • Halter traction • Head extended vs neutral • Radiolucent mouth prop

41. Anterior Odontoid Screw: Surgical Approach • Low cervical incision (C5-6) • Standard approach to C-spine • Modified Caspar retractor • Prevertebral space opened to C2 • Angled retractor to create tunnel to C2

42. Anterior Odontoid Screw: Surgical Approach • K-wire placed on A-I lip of C2 • 8mm hand-operated hollow drill over K-wire • Trough in body of C3 • Incise C2-3 annulus • C2 body not disrupted • Extend neck if retrolisthesis of dens present

43. Ant Odontoid Screw: Surgical Approach • Drill guide system over K-wire • Spike on outer tube impacted into C3 • K-wire removed and replaced with drill • Drill to apex of odontoid • Pilot hole through apical cortex of odontoid

44. Ant Odontoid Screw: Surgical Approach • Pilot hole is tapped • Lag screw inserted through the guide tube • Image saved for comparison • Final screw placed • Stabilization confirmed by flex/ext of neck • Procedure repeat if second screw needed, but no lag screw required

45. Anterior Odontoid Screw Fixation

46. Anterior C1-2 Transfacetal Screw Fix • Expose identical to ant odontoid screw fix • Facet joints are decorticated with angled curette • Screws placed into the C2 vertebral body in the groove between the body and superior C2 facet • Angle of drilling adjusted in a superiolateral direction to allow for passage through lateral mass of C2, across C1-2 joint space and into C1 lateral mass • Maintains some C1-2 motion vs [posterior] transarticular screw???

47. Case Presentation

48. Case Presentation

49. Case Presentation

50. Summary • Odontoid fracture cause by flexion/extension loading • Type 1 usually treated with collar unless AOD • Type III treated with brace/halo unless disrupted transverse ligament or fails conservative treatment • Treatment of type II controversial but surgical intervention usually recommended due to high rate of non-union (27-75%) • Direct anterior odontoid screw preserves cervical rotation and offers immediate stabilization but needs intact TL; if type III fx then must be simple • Posterior bone and wiring fusion is gold standard • Posterior instrumentation (transarticular, lateral mass, pedicle, translaminar screws) offer immediate rigidity and superior stabilization/?fusion