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 Spinal Canal 1/3 cord 1/3 dens 1/3 empty
Rule of thirds

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

9. Types of Odontoid Fractures
Anderson and D’Alonzo classification (1974):
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

10. Types of C2 Fractures

11. Hangman Fractures http://www.nypemergency.org
Hangman fracture is fracture through pedicles of C2.
Misc- R sup facet fx

12. Jefferson Fractures Unilateral/bilateral Ant + Post arch of C1
Axial loading to head(ex: diving)

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
1.5 to 2 mm cuts to avoid volume averaging

19. Type III Odontoid 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
Type I
Type II
Type III
No AOD
AOD
???
MRI
TL intact
TL disrupted
Halo x 12 weeks
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. Non-union of Type II Odontoid Fractures Treated Conservatively
AUTHOR AND YEAR
NO. OF PATIENTS
NONUNION RATE (%)
SIGNIFICANT FACTORS
Anderson & D'Alonzo, 19747 49 36
None specified
Apuzzo et al, 45 33
Age >40 yr, displacement >4 mm
Ekong et al, 17 41
Age ≥55 yr, displacement >4-6 mm
Hadley et al, 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, 42 50
Age >72 yr, posterior displacement
Schweigel, 47 10
Not age, not displacement
Hadley et al, 19892 65 28
Not age, displacement ≥6 mm
Ryan & Taylor, 35 77
Posterior displacement
Seybold & Bayley, 37 29
Not age, displacement unknown
Greene et al,
Displacement ≥6 mm
Seybold and Bayley34 reviewed the functional outcome of patients with dens fractures based on the patient's age and type of fracture. They documented an overall fusion rate of 65% for patients with type II odontoid fractures treated with halo immobilization and found no statistically significant difference in the rate of fusion for patients younger than 60 years and for those older than 60 years. Further, the degree of displacement did not significantly affect the rate of fusion.
Greene and colleagues35 reviewed their experience with 340 acute axis fractures. They identified two categories of unstable type II fractures that should be seriously considered for early surgical fusion. The first category was composed of patients with dens displacement of 6 mm or greater-the single most significant factor associated with nonunion after nonoperative treatment. The second category was composed of patients with comminuted dens fractures.20
In an earlier review by Hadley and coworkers12 of the initial 107 patients in this group, there was a high incidence of failure after nonsurgical management of patients with more than a 6-mm offset of the odontoid in any direction. They found a 67% nonunion rate in patients with 6-mm or greater subluxation, compared with a 9% nonunion rate in patients with lesser degrees of subluxation. Neither the patient's age nor the direction of subluxation correlated with the risk of nonunion. In an additional review of 229 patients from this same group, there were similar results.2
Bettini and colleagues32 reviewed 17 patients treated with either a halo or a Minerva brace and found an overall successful fusion rate of 71%. Displacement greater than 2 mm was associated with fusion failure.
Dunn and Seljeskog9 studied 59 patients with type II odontoid fractures and found that patients older than 65 years had a high risk of nonunion with conservative management. Patients whose odontoid was displaced posteriorly were less likely to heal. The reported rate of nonunion was 70% in patients with retrolisthesis, compared with 30% in patients with anterolisthesis.
Apuzzo and colleagues26 reported an 88% nonunion rate for patients with more than a 4-mm subluxation, compared with 16% for patients with less than a 4-mm displacement. They also observed a higher rate of nonunion among patients older than 40 years. They concluded that external immobilization was appropriate for all nondisplaced type II odontoid fractures, but patients with fractures displaced more than 4 mm were candidates for early surgical fusion. Their patients were treated with a variety of cervical collars and braces, many of which provided less stability than a halo brace.

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
Gallie, Brooks-Jenkins, Sonntag, Lockley all contributed to our understanding of C1-2 fusion.

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
Traynelis- review article

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

30. Interspinous Wiring
C1: wire passed though drilled-out holes in posterior tubercle
C2: wire passed beneath SP
Technique originated by Rogers, modified by Whitehill, Benzel, Kesterson, and Murphy and Southwick.
Bone graft between C1 and C2 laminae.

31. Facet/Transarticular Wiring
Useful when the posterior elements are unavailable as fixation points (fractures, surgical removal).
Callahan (1977).
1.Expose lateral masses. 2.Remove facet capsular ligaments. 3. Open facet joint. 4. Drill hole perspendicular to interior articular process at C1 and C2. 5. Wire or cable is passed in a rostral-to-caudal direction and exits through the joint space. 6. The wires are wrapped around bone graft and fastened. The caudal end of the bone graft can be secured to the spinous process, thus sparing the caudal facet joint.

32. Interlaminar Wiring
Requires intact laminae; May increase canal stenosis--> neurologic injury (technique abandoned by most).
Bilateral placement of interlaminar clamps (such as Halifax clamps first described by Tucker, 1975).
Leading edge of the C1 lamina and trailing edge of the C2 lamina thinned bilaterally to augment the interlaminar spaces. An autologous strut graft can be interposed between the spinous processes to prevent hyperextension and promote fusion.

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
Biomechanical studies have demonstrated superior rotational stability at facets compared to wiring.

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
(The above slide applies to subaxial lateral mass screws).
Original description by Roy-Camille.
3 modifications by: 1) Magerl; 2) Anderson; and 3) An. The screw is generally directed superiorly and laterally to avoid the nerve root. In one study performed in human cadavers, the investigators found that, of these modifications, the An technique demonstrated the lowest risk of nerve root damage due to overpenetration in drilling or insertion of too long a screw. In another cadaver study, it was found that if a screw 15 mm or shorter was used, the chances of injury to the vertebral artery or nerve root were minimized in all three techniques.
Left: The Magerl technique. The entrance point for screw insertion is located slightly medial and rostral to the midpoint of the lateral mass. The direction of the screw is 25° laterally in the axial plane and parallel to the facet joint in the sagittal plane. Center: The Anderson technique. The entrance point for screw insertion is located 1 mm medial to the midpoint of the lateral mass. The direction of the screw is 10° lateral in the axial plane and 30 to 40° rostral in the sagittal plane. Right: The An technique. The entrance point for screw insertion is located 1 mm medial to the midpoint of the lateral mass. The direction of the screw is 30° lateral in the axial plane and 15° rostral in the sagittal plane.

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)
Abumi, et al. (1994) were the first to report the successful use of cervical pedicle screws.
In biomechanical studies conducted in animal models and human cadavers-- superior stability, fixation, and resistance to screw pullout forces compared with lateral mass plating.
Once the posterior elements are exposed to the lateral margin of the articular masses, the point of pedicle screw insertion is penetrated with a high-speed drill.
The angle at which the screw is inserted can vary from 25 to 45° medial to the midline in the transverse plane (B). In the sagittal plane, the angle of insertion should be parallel to the upper endplate for the pedicles of C-5 to C-7, and in a slightly cephalad direction for the pedicles of C-2 to C-4 (C). After making the entrance hole, a fluoroscopy-guided small pedicle probe is inserted into the pedicle. Thereafter, the appropriate pedicle screw is tapped and inserted. Plates, rods, and bone graft are applied to promote fusion.

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)*
Bohler (1982/1968) and Nakanishi (1980) first reported this method.
Fractures with an anterior oblique orientation were significantly more likely to result in nonanatomic fusion, fibrous union, or nonunion than were posterior oblique and horizontal fractures.
Obliquely anteriorly sloping fractures may allow the dens to slide anteriorly along the fracture line as the lag screw pulls it inferiorly. This situation seldom occurs with acute fractures because the irregular bone surfaces engage and lock together, but it can be a problem with fractures that are a few weeks to several months old.
* Posterior fusion
Apfelbaum RI: Anterior Screw Fixation of Odontoid Fractures (Aesculap Scientific Info 24). Tuttlingen, Germany, Aesculap AG, a. Apfelbaum RI, Lonser RR, Veres R, et al: Direct anterior screw fixation for recent and remote odontoid fractures. J Neurosurg 93(2Supp):

40. Anterior Odontoid Screw: Surgical Approach
Prone
Shoulder roll
Halter traction
Head extended vs neutral
Radiolucent mouth prop
Shoulder roll to increase neck extension in this patient, whose fracture was reduced during extension. Two C-arm fluoroscopic units are used for anteroposterior (transoral) and lateral fluoroscopic imaging.
Gentle halter traction is applied. If the patient's fracture reduces with extension, the head is placed in an extended position; if not, a neutral position is initially used, with a support placed behind the patient's head. Head positioning is monitored with lateral C-arm fluoroscopy. If available, a second C-arm unit greatly facilitates the procedure. It is positioned for anteroposterior (transoral) odontoid viewing, using a radiolucent (plastic or cork) 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
To achieve a trajectory low enough for proper screw placement, the cervical spine is approached through a low cervical incision (at approximately C5-6). A standard approach to the anterior cervical spine is used, followed by placement of a modified Caspar retractor system beneath the bellies of the longus colli muscles. The prevertebral space is then opened to the C2 region, and an angled retractor is inserted into the space to create a tunnel up to C2, through which the remainder of the procedure is completed

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
Under biplanar fluoroscopic guidance, a Kirschner wire (K-wire) is positioned on the anteroinferior lip of C2 at the exact entrance site desired for the fixation screw. An 8-mm hollow drill is placed over the K-wire and rotated by hand to create a shallow trough in the body of C3 and to incise the C2-3 annulus without cutting into the C2 body (see Fig C and D). The drill guide system is placed over the K-wire.
In patients with retrolisthesis of the odontoid, the support behind the patient's head is removed at this juncture. As the patient's head is extended, the alignment is maintained by exerting downward pressure on the C2-3 complex. In this manner, alignment is perfected while the neck is extended as needed to obtain the proper drill trajectory

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
The drill guide system consists of inner and outer tubes that are mated and then placed over the Kirschner wire (K-wire). The spikes on the outer guide tube are impacted into C3 to stabilize the system. B, The K-wire is removed and replaced with the drill, which is fluoroscopically guided to the apex of the odontoid after the fracture is reduced. A pilot hole is drilled through the apical cortex of the odontoid. If the distal cortex is not penetrated by the drill, screw placement may be difficult or impossible.

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
Because the angle of drilling is coaxial with the long axis of the odontoid, penetration into the spinal canal toward the spinal cord is unlikely. Frequent biplanar imaging controls the drilling process. The pilot hole is then tapped, and a lag screw is inserted through the guide tube using a special screwdriver with an internal retaining spring to hold the screw (Fig ). The image with the drill in its final position is saved and compared with the live image. An identical position can thereby be achieved when tapping and placing the screw. Stabilization can be confirmed by flexing the patient's neck under fluoroscopic guidance.
A lag screw is placed for the first screw to draw the odontoid down toward the body of C2. If a second screw is used, it can be fully threaded.

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
18 y/o previously healthy male, +EtOH, tripped and fell while being pursued. c/o neck pain on presentation to ED. Initial xrays of C-spine were suspicious for odontoid fracture. Pt subsequently obtained CT of C-spine.

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

51. References
Anderson LD, D'Alonzo RT: Fractures of the odontoid process of the axis. J Bone Joint Surg Am 56: ,
Apuzzo ML, Heiden JS, Weiss MH, et al: Acute fractures of the odontoid process: An analysis of 45 cases. J Neurosurg :85-91, 1978.
Clark CR, White AA III: Fractures of the dens: A multicenter study. J Bone Joint Surg Am 67: , 1985.
Dunn ME, Seljeskog EL: Experience in the management of odontoid process injuries: An analysis of 128 cases. Neurosurgery 18: , 1986.
Ekong CE, Schwartz ML, Tator CH, et al: Odontoid fracture: Management with early mobilization using the halo device. Neurosurgery 9: , 1981.
Greene KA, Dickman CA, Marciano FF, et al: Acute axis fractures: Analysis of management and outcome in 340 consecutive cases. Spine 22: , 1997.
Hadley MN, Browner C, Sonntag VKH: Axis fractures: A comprehensive review of management and treatment in 107 cases. Neurosurgery 17: , 1985.
Hadley MN, Browner CM, Liu SS, et al: New subtype of acute odontoid fractures (type IIA). Neurosurgery 22:67- 71, 1988.
Hadley MN, Dickman CA, Browner CM, et al: Acute axis fractures: A review of 229 cases. J Neurosurg 71: , 1989.
Hanssen AD, Cabanela ME: Fractures of the dens in adult patients. J Trauma 27: , 1987.Winn, Richard. Youmans Neurological Surgery. 5th edition.
Ryan MD, Taylor TK: Odontoid fractures: A rational approach to treatment. J Bone Joint Surg Br 64: ,
Seybold EA, Bayley JC: Functional outcome of surgically and conservatively managed dens fractures. Spine 23: , 1998.

52. References http://www.medscape.com
Netter, Frank. Atlas of Human Anatomy.
Schmidek and Sweet. Operative Neurosurgical Techniques. 3rd edition.
Schweigel JF: Management of the fractured odontoid with halo-thoracic bracing. Spine 12: , 1987.