Upper C-spine Fractures Azam Basheer

Upper C-spine Fractures

Azam Basheer MD

Henry Ford Neurosurgery

Outline

• Epidemiology

• Anatomy

• Common Injuries

• Management and surgical approaches

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Case 1

37 y/o F s/p high speed MVA restrained passengerAzam Basheer

Case 2

47 y/o M s/p T-bone MVA, head impact against driver-side window

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Case 3

56 y/o s/p fall from ladder with left delt weaknessAzam Basheer

Epidemiology

• Represents 23-30% of all spine fractures

– Cause

• MVA 42%

• Fall 20%

• Violence 16%

– Gender

• Male 81%

• Female 19%

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Source: National Spinal Cord Source: National Spinal Cord Injury Statistical Center, University of Alabama at Birmingham, 2004

Annual Statistical Report, June, 2004 Injury Statistical Center, University of Alabama at Birmingham, 2004

Anatomy

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Anatomy – The Ligaments

– Internal (within spinal canal):

• Tectorial membrane: thickening of PLL

• Cruciate ligament – including transverse ligament

• Alar and apical ligaments

– External

• Anterior and posterior atlanto-occipital membranes

• Anterior and posterior atlanto-axial membranes

• Articular capsules

• ligamentum nuchae

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- Transverse Occipital Lig:

-Prevents posterior

displacement of the apex

of the dens

- Accessory Atlantoaxial Lig:

-Limits axial rotation

Ligaments cont.

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The Barkow Ligament

- Anteromedial occipital

condyles

- Sits anterior to the

apex of dens

- Limits extension of the

dens tip

Tubbs et al. Ligaments of the craniocervical junction.

J Nsurg: Spine Vol 14 / June 2011

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Vertebral Artery

• Arises from subclavian artery

• Enters foramen

transversarium at C6

• Turns laterally at C2

• Travels posteriorly at C1

(vertebral groove)

• Ascends superiorly along

clivus

http://www.maitrise-

orthop.com/corpusmaitri/orthopaedic/mo

68_laude/index.shtml

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Degrees of motion

Flexion

• Oc-C1 is 10°

• C1-C2 is 5 °

Extension

• Oc-C1 is 25 °

• C1-C2 is 10 °

Rotation

• Oc-C1 is 0°

• C1-C2 is 45 °

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Anatomic Measurements

Steele’s Rule of Thirds

http://www.pt.ntu.edu.tw/hmchai/Kines04/KINspine/Spine.files/AAAjointSup.jpg

• 1/3 cord

• 1/3 dens

• 1/3

Subarachanoid

space/empty

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The Atlantodental Interval (ADI)

• First described by Hinck et al

• Used to evaluate the atlanto-axial relationship

• Normal < 3 mm in men; <2.5 mm in women; <5 mm in children under 9

• Enlargement of the predental space points to injury of the transverse ligament

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Posterio-atlanto Dens Interval

(PADI)

- Represents the

anteroposterior diameter

of the spinal canal at this

level

- More useful

prognosticator in

rheumatoid arthritis

patients than the ADI

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Harris lines

- Used to evaluate osseous relationships at the craniocervical junction

– Basion-Dens Interval: In 95% of adults, the basion-dens interval <12 mm

– Basion–Posterior Axial Line Interval: in 98%, the basion was situated no more than 12 mm anterior or 4 mm posterior to the posterior axial line

• “Rule of Twelve”Azam Basheer

Harris Lines

An abnormal distance between the dens or posterior axial line and the basion

suggests failure of the alar ligaments, tectorial membrane, or both.

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• First described by Powers et al, 1979

• Basion-Post. C1 arch divided by Opisthion-Ant. C1 arch

– >1 considered abnormal

• Limited Usefulness

• Positive in Anterior Translational injuries

• False Negative with pure distraction

Powers’ Ratio

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Lee’s Lines

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Rule of Spence

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Imaging

• MR imaging of the cervical spine with T2-weighted fat-suppressed gradient-echo or STIR sequences useful in assessing the integrity of ligaments.

Warner et al. Magnetic resonance imaging of ligamentous injury of the cervical spine. Emerg Radiol 1996; 3:9–15.

Dickman et al. Magnetic resonance imaging of the transverse atlantal ligament for the evaluation of atlantoaxial instability. J Neurosurg 1991; 75:221–227.

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Upper C-spine Injuries

Upper C-spine Injuries

• Atlanto-occipital dislocation

• Condylar fractures

• Atlas fractures

• Odontoid fractures

• Hangman's fractures

• Misc. fractures

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Atlanto-Occipital Dislocation

(AOD)

AOD

• Aka Craniocervical Dissociation, “internal decapitation”

• Cause of death in ~10% of fatal c-spine injuries

• Due to rupture of the alar ligaments, the tectorial membrane,

and the occipito-atlantal joint capsules

• May cause a SAH at the CCJ

• Mechanism:

• flexion and distraction

• rotation and hyperextensionAzam Basheer

AOD

• Established criteria for diagnosis of AOD:– BDI >12 mm, or

– BPALI >12 mm posterior to basion, or

– BPALI >4 mm anterior to basionAzam Basheer

Traynelis Classification of AOD

Type I Type II Type III

anterior subluxation

most common

vertical distraction

>2 mm of the

atlanto-occipital joint

posterior dislocation

rarely reported

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AOD Treatment

• AVOID traction

• Halo until surgery

• 1º treatment:

– Oc-C2 or C3 fusion

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Occipital Condyle Fractures

Occipital Condyle Fractures

• First described in 1817 by Sir Charles Bell at an autopsy of a fall victim

• Associated with some C1 fx and palsies of lower cranial nerves

• Hypoglossal n. most often involved due to fx extension through the hypoglossal canal

• Anderson and Montesano(1988) classification

Anderson et al., SPINE, 1988

Tuli et al., Neurosurgery, 1997

Sir Charles Bell

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Type I

-An impaction-type fx due to axial

loading resulting in a

comminuting fracture of the

occipital condyle

- Stable because the tectorial

membrane and alar ligament are

intact

- Collar 6-8 weeks

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Type II

- A basioccipital fracture,

that extends to the

condyle

- Due to a direct blow to

the skull

- An intact tectorial

membrane and alar

ligaments preserve

stability

- Collar 6-8 weeks

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Type III

• avulsion fx at the site of the alar ligament resulting in fragment displacement into the foramen magnum

• Due to forced rotation, usually combined with lateral bending

• Potentially unstable – due to ligamentous disruption

• Minimally displaced Halo vest, 8-12 weeks

• Displaced O-C2 fusion

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C1 Fractures

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Fractures of C1

Account for 3-13% of C-spine fractures

Four types of atlas fractures

Type I:

- Isolated fractures of the anterior arch of C1

anterior arch fractures

- Usually avulsion fx

- low morbidity and little clinical

significance

- Plough fractures

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Plough Fracture

- Displaced fx of the anterior arch

- Hyperextension shears off the

anterior arch, a mechanism that

has been likened to a plough

- Can be associated with AOD

- Reduction with halo in slight

flexion or Oc/C1-C2

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Fractures of c1

Type II:

- Isolated fractures of the posterior arch

of C1

- Typically caused by hyperextension

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Fractures of c1

Type III:

- fracture through the lateral mass of C1

- rotation or lateral flexion forces

- Radiographically, asymmetric displacement of the lateral masss

- low morbidity and little clinical significance.

- C-collar if ligament intact vs. halo

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Transverse ligament avulsion

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Jefferson Fracture

Sir Geoffrey Jefferson M.D.

Type IV:

-Burst fracture of the ring of C1 (Jefferson fracture)

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Jefferson Fractures

http://uuhsc.utah.edu/rad/medstud/NeuroCaseStudies/Images/Neuro%20Case%2015

%20jefferson%20fracture.jpg

• Ant AND Post arch of C1

• Unilateral/bilateral

• Axial loading (diving)

• ~5% neurologic deficit as the ring of C1 widens when it fractures limiting cord compression

• ~1/3 are associated with a C2 fracture

• Non-displaced Jefferson fx (<7mm overhang)

• Halo for displaced

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C2 Fractures

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Types of C2 Fractures

Represent ~20% of C-spine fx

http://www.nypemergency.org

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Odontoid Fractures

- Represent 60% of C2 fractures

- Neurological deficits in 10-20%

- Etiology Bimodal - Young - high energy, multi-trauma

- Elderly - low energy, isolated injury

Mechanism of injury:

• Flex loading anterior displacement of dens (more common)

• Ext loading posterior displacement of dens (ex: fall on forehead)

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2 %

50-75 %

15-25 %

Anderson and D’Alonzo classification (1974)

Odontoid Fractures

Fracture Feature Stability

Type I

Small oblique

avulsion of

upper 1/3 of

odontoid (alar

ligament)

Stable if No

AOD and TL

intact

Type II

Fracture at

junction of

dens and C2

Unstable

Type IIa

Comminuted

fracture at

base of

odontoid

Unstable

Type III

Fx through

body of C2, incl

one or both

sup articular

processes

Usually

stable

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Dens Fxs: Non-surgical Management

External immobilization

- Collar vs Brace vs Halo

- 45% restriction w/ conventional braces

- 75% upper cervical motion restriction w/ halo

- 10-77% non-union rate with external fixation

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Non-union of Type II Odontoid Fractures Treated Conservatively

AUTHOR AND YEAR NO. OF PATIENTS NONUNION RATE (%) SIGNIFICANT FACTORS

Anderson & D'Alonzo, 1974 49 36 None specified

Apuzzo et al, 1978 45 33Age >40 yr, displacement >4

mm

Ekong et al, 1981 17 41Age ≥55 yr, displacement >6

mm

Hadley et al, 1985 40 26Not age, displacement >6

mm

Clark & White, 1985 106 32Not age, displacement >5

mm

Dunn & Seljeskog, 1986 88 24Age >65 yr, posterior

displacement

Hanssen & Cabanela, 1987 42 50Age >72 yr, posterior

displacement

Schweigel, 1987 47 10 Not age, not displacement

Hadley et al, 1989 65 28Not age, displacement ≥6

mm

Ryan & Taylor, 1993 35 77 Posterior displacement

Seybold & Bayley, 1998 37 29Not age, displacement

unknown

Greene et al, 199735 88 28 Displacement ≥6 mm

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Non-surgical Management

• Higher risk of non-union:– displacement > 6mm

– >6mm – nonunion rate 67%

– <6mm – nonunion rate 9%

– Posterior displacement– Non-union rate of 70-89%

– Angulation > 100

– Age > 50

– Smoking

– Delay in diagnosis > 3 weeks

– Inability to achieve or maintain reduction

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Dens Displacement

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Dens Angulation

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Type II Dens Surgical tx

Surgery for:– >6mm displacement (>6 mm displacement and >60 years, 85% nonunion rate)

– Age>65

– Fracture cannot be maintain by external orthosis

– Rupture of transverse ligament

Type of surgery:

-Intact transverse ligament

* Anterior Odontoid Screw fixation

-Disrupted TL

*C1-2 posterior fusion

-Transarticular screw fixation (Magerl and Steeman Cerv Spine 1987, Reilley et

al, JSD 2003)

-C1 lateral mass – C2 pars/pedicle screw

-Posterior wiring

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Algorithm for Treatment of Odontoid Fractures

Odontoid Fractures

Type I Type II Type III

AOD Surgery

vs

Brace/halo

MRI

TL intactTL disrupted

Comminuted

Posterior

Fusion

No AOD

SurgeryCollar

Post fusion

Simple fx

Ant vs post fus

Brace/halo

Fails

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Hangman’s Fracture

- AKA Traumatic spondylolisthesis

- Bilateral arch fracture of C2 (pars)

- Younger age group (Avg 38 yrs)

- Usually due to hyperextension-axial compression forces (windshield strike)

- Neurologic injury seen in only 5-10 %

• Effendi Classification Levine & Edwards, and Sonntag & Dickman

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Type I Hangman’s

• Most common

• Bilateral pars fractures with

translation <3 mm and NO

angulation

• Axial loading and then

extension

• Stable collar

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C2-3 Angulation

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Type II Hangman’s

• C2-3 disc and PLL disruption – >3 mm displacement of C2 on C3 or

– >11o angulation

• ALL generally remains intact but is stripped from its bony attachment

• extension, and then rebound flexion

• Unstable

– Halo if reducible vs.

– posterior approach C1-C3, or C2–C3 anterior discectomy and arthrodesis

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Type IIA Hangman’s

• Less common

• Little to no translation, but significant <11o

angulation

• Unstable

– Halo if reducible vs.

– posterior approach C1-C3, or C2–C3

anterior discectomy and arthrodesis

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Type III Hangman’s

• Pars fracture with dislocation of the C2-3 facet joints (facet capsules are disrupted)

• Unstable

• The most common injury to be associated with neurological deficit

• Requires surgery

• Options: Anterior C2-3 discectomy and fusion, or posterior open reduction and C1-3 fusion Azam Basheer

Surgical Approaches to C1-2

fusion

Surgical Approaches to C1-2

fusion• Anterior odontoid screw fixation

• Posterior bone and wire fusion

• Posterior transarticular screw fixation

• Posterior fusion with lateral mass

screws/rods

• Posterior fusion with pedicle screws/rods

• Posterior fusion with translaminar

screws/rods

• Anterior transfacetal screw fixationAzam Basheer

Anterior vs Posterior

Approach for Dens fx

• Posterior fusion eliminates atlantoaxial

rotation, usually noticeable by patient

• Odontoid screw fixation: provides immediate

stabilization, promotes bone healing,

preserves C1-2 rotation

• Anterior approach more morbid due to

extensive neck dissectionAzam Basheer

Anterior Odontoid Screw Fixation

Indications • Type II and Shallow Type III

• Unable to tolerate halo-vest

• Early displacement despite halo-vest

Contraindications• Non-reducible odontoid fracture

• Body habitus (Barrel chest )

• Associated Transverse ligament injury

• Subacute injury (> 6 months)

• Reverse oblique

• Relative contraindications: smoking, age >60Azam Basheer

Surgical Approach

• Prone

• Shoulder roll

• Halter traction

• Head extended vs neutral

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.

Surgical Approach

• Low cervical incision (C5-6)

• Standard approach to C-spine

• Angled retractor to create tunnel to C2

• K-wire placed on ant-inf lip of C2

• 8mm hand-operated hollow drill over K-wire

• Trough in body of C3

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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

• place screw

• Stabilization confirmed by flex/ext of neckAzam Basheer

Posterior C1-2 Approaches

POSTERIOR WIRING

TECHNIQUES• Require intact posterior arch of C1 and C2

• Contraindicated

– Posterior decompression of C1-C2 required

– Significant osteoporosis

– Rheumatic involvement of the atlas

– Posterior rachischisis

• Requires sublaminar passage of a cable

– Potential for injury to Dura or spinal cord

– Need for long term post-op halo immobilization

– Requirement for intact posterior vertebral elements

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Interspinous Wiring

Technique originated by

Rogers, modified by Whitehill,

Benzel, Kesterson, and Murphy

and Southwick.

Bone graft between C1 and C2

laminae.

C1: wire passed though drilled-

out holes in posterior tubercle

C2: wire passed beneath SP

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GALLIE FUSION

Posterior interspinous fusion with sublaminar wires and iliac grafts

Median autograft from iliac crest notched over the spinous process of C2

Sublaminar wire placed around the posterior arch of C1and wraps around the spinous process of C2

Stabilization– Comparable stabilization in A/P

translation in response to flexion– Poor stabilization in rotation

• Patients require increased post-op external immobilization

• Successful fusion rate 75%

http://emedicine.medscape.com/article/1343720-media

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Brooks-Jenkins Fusion

• Modification to overcome the rotational deficiencies of Gallie Fusions

• Bilateral interlaminar bone grafts

• Requires passage of bilateral sublaminar cables beneath C1 and C2

• Fusion rate ~ 93%

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SONNTAG’S MODIFIED GALLIE

FUSION

• Decreases risk of cord injury at C2 by eliminating sublaminar wires

• Single bicortical bone graft fit into interlaminar space

• Requires widening of C1-2 interlaminar space

• Pt kept in halo pre-op, intra-op, and post-op halo for 3 months

• Fusion rate ~ 97%

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LOCKSLEY INTERSEGMENTAL TIE-

BAR TECHNIQUE

• 3 point fixation with immediate rigidity and resistance to all axis of movement

• Grafts secured with sublaminar wires in figure-8 pattern

• Posterior stabilization plate Secured by wires to post. Spinous process

• Can be applied to any cervical segment

• Rib graft is ideal, but iliac autograft can also be used

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Facet/Transarticular Wiring

Useful when the posterior elements

are unavailable Callahan (1977).

1.Expose lateral masses

2.Remove facet capsular ligaments

3. Drill hole perpendicular to interior

articular process at C1 and C2

4. Wire or cable is passed in a

rostral-to-caudal direction and exits

through the joint space.

5. 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.

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Interlaminar Wiring

- Bilateral placement of interlaminar

clamps Tucker, 1975.

- Requires intact laminae; May increase

canal stenosis--> neurologic injury

-Good stability with

flexion/extension

-Poor rotational stability

- Laminae thinned bilaterally to augment

the interlaminar spaces.

- Strut graft placed between the spinous

processes to prevent hyperextension

and promote fusion

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TRANSARTICULAR SCREW OF

MAGERL

• Unilateral/Bilateral

• 3.5mm screw through the C2 pedicle,

across the C1-2 facet, and into lateral

mass of C1

• C1 and 2 become rigidly coupled

• Wire passed around posterior arch of

atlas for gentle retraction on atlas

• Entry point 2mm lateral and 2mm

above the medial aspect of C2 inferior

facet

• Trajectory of the drill exits C2 at

posterior edge of superior articular

surface near the isthmus of the pedicle

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TRANSARTICULAR SCREW OF

MAGERL

• Post-Op– Hard collar for 6 weeks

• Stability– Successful fusion rates between 86.9-100%

– Construct stable in F/E and rotation

• Complications

– Madawi et al.• Malpositioned screws in 14%

• Vertebral artery injury in 8%

• Hardware failure in 4%

• Temporary hypoglossal nerve paresis in 2%

• Iliac crest donor site infection in 2%

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Posterior C1-2 Fusion with

Lateral Mass Screws

• Useful when posterior

elements absent or

disrupted

• biomechanically better

rotational stability at

facets vs wiring

• Immediate rigidity

-better fusion

-no halo

Harms J, Melcher RP. Posterior C1–C2 fusion with polyaxial screw and rod fixation. Spine 2001;26:2467–71.Azam Basheer

GOEL’S/HARM’S TECHNIQUE

• Fixation using independently placed screws into the C1 lateral mass and C2 pedicles, connected with posterior rods or plates

• Goel originally developed the technique using monoaxial screws and plates, but Harm later modified the procedure to use polyaxial screws and rods

Mummaneni, P. et al. Atlantoaxial fixation: overview of all techniques.

Neurology India. December 2005. Vol 53, Issue 4. 408-415Azam Basheer

GOEL’S/HARM’S TECHNIQUE• Exposure

– Midline incision from suboccipital to spinous process of C3

– C2-C3 facet joint and C1 posterior arch exposed

– Vertebral artery in vertebral groove on superior aspect of C1 arch

– Medial wall of C1 lateral mass is medial limit for screw

– Medial aspect of transverse foramen is lateral limit

• Entry point – center of C1 lateral mass

– 3-5 mm lateral to medial lateral mass

Mummaneni, P. et al. Atlantoaxial fixation: overview of all techniques. Neurology India. December 2005. Vol 53, Issue 4. 408-415

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Posterior C1-2 Fusion with

Pedicle Screws

• Abumi, et al. (1994) : cervical pedicle

screws

• 3 column fixation

• Biomechanically superior to lateral

mass screws

• Enter lateral to center of facet, close

to post margin of superior articular

surface

• The angle can vary from 25 to 45°

medial to the midline

• slightly cephalad direction for the

pedicles of C-2 to C-4

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Posterior C1-2 Fusion with

Translaminar Screws

• First presented in 2003

• Technique published in

2004

• Minimize injury to

vertebral artery

• Crossing, bilateral

translaminar screws

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WRIGHT TECHNIQUE

• Open a cortical window at the junction of the C2 spinous process and lamina

• Insertion of polyaxial screws into the laminae of C2 in a bilateral crossing fashion

• The C1 lateral mass screws are connected to the crossing, bilateral C2 laminar screws with posterior rods

– Safer rigid fixation of C2

– Low risk to vertebral arteries

– Requires intact posterior elements of C2

C1

C2

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Case 1

37 y/o F s/p high speed MVA restrained passenger

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Case 1

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Case 2

47 y/o M s/p MVA Halo Azam Basheer

Case 3

56 y/o s/p fall from ladder with left delt weaknessAzam Basheer

References•Anderson LD, D'Alonzo RT: Fractures of the odontoid process of the axis. J Bone Joint Surg Am 56:1663-1674, 1974.

•Clark CR, White AA III: Fractures of the dens: A multicenter study. J Bone Joint Surg Am 67:1340-1348, 1985.

•Wright et al. Vertebral artery injury in C1-2 transarticular screw fixation. J Neurosurg. 8, 1998

•Dunn ME, Seljeskog EL: Experience in the management of odontoid process injuries: An analysis of 128 cases. Neurosurgery 18:306-310, 1986.

•Ekong CE, Schwartz ML, Tator CH, et al: Odontoid fracture: Management with early mobilization using the halo device. Neurosurgery 9:631-637, 1981.

•Greene KA, Dickman CA, Marciano FF, et al: Acute axis fractures: Analysis of management and outcome in 340 consecutive cases. Spine 22:1843-1852, 1997.

•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 71:642-647, 1989.

•Hanssen AD, Cabanela ME: Fractures of the dens in adult patients. J Trauma 27:928-934, 1987.Winn, Richard. Youmans Neurological Surgery. 5th edition.

•Ryan MD, Taylor TK: Odontoid fractures: A rational approach to treatment. J Bone Joint Surg Br 64:416-421, 1982.

•Seybold EA, Bayley JC: Functional outcome of surgically and conservatively managed dens fractures. Spine 23:1837-1846, 1998. Menendez et al. Techniques of Posterior C1-C2 Stabilization. Neurosurgery 60:1, 2007

•Vender et al. The evolution of posterior cervical an occipitocervical fusion and instrumentation. Neurosurgical Focus 16:1, 2004

•Poliaksiyal et al. Posterior atlantal lateral mass fixation technique with polyaxial screw and rod fixation system. Turkish neurosurgery 18:2, 2008

•Dickman et al. Biomechanical characteristics of C1-2 cable fixations. J Neurosurg. 85, 1996

•Goel et al. Plate and screw fixation for atlantoaxial subluxation. Acta Neurochir. 129

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References cont.• Hanson et al. Anatomic and biomechanical assessment of transarticular screw fixation for atlantoaxial instability. Spine 16, 1991

• Magerl et al. Stable posterior fusion of the atlas and axis by transarticular screw fixation. Spine. 1987

• Paramore et al. The anatomical suitability of C1-2 complex for transarticular screw fixation. J Neurosurg 85, 1996

• Vikas et al. Spine Trauma: Surgical Techniques. Springer. 2010

• Hadley MN, Browner C, Sonntag VKH: Axis fractures: A comprehensive review of management and treatment in 107 cases. Neurosurgery17:281-290, 1985.

• Suchomel et al. Reconstruction of Upper Cervical Spine and Craniovertebral Junction. Springer, 2011

• Stulik et al. Harms technique of C1-C2 fixation with polyaxial screws and rods. Acta Chir Orthop Traumatol Cech. 2005; 72(1):22-7

• Hu et al. Posterior cervical spine arthrodesis incorporating C2 laminar screw fixation in the treatment of cervical spine injury. Orthopaedic Surgery. 2:1;32-37. 2010

• Apuzzo ML, Heiden JS, Weiss MH, et al: Acute fractures of the odontoid process: An analysis of 45 cases. J Neurosurg 48:85-91, 1978.

• Rhee et al. Modified trajectory of C2 laminar screw – double bicortical purchase of the inferiorly crossing screw. J Korean Neurosurg Soc. 43(2). 2008

• Senoglu et al. C2 intralaminar screw placement: a quantitative anatomical and morphometric evaluation. Turkis neurosurgery; 19, 2009

• Mummaneni et al. Atlantoaxial fixation: overview of all techniques. Neurology India. 53. 2005

• Song et al. Surgical treatment of craniovertebral junction instability: clinical outcomes and effectiveness in personal experience. J Korean Neurosurg 48, 2010

• Warner J, Shanmuganathan K, Mirvis SE, Cerva D. Magnetic resonance imaging of ligamentous injury of the cervical spine. Emerg Radiol 1996; 3:9–15.

• Dickman CA, Memourian A, Sonntag VKH, Drayer BP. Magnetic resonance imaging of the transverse atlantal ligament for the evaluation of atlantoaxial instability. J Neurosurg 1991; 75:221–227.

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References cont.

•http://www.medscape.com

•Netter, Frank. Atlas of Human Anatomy.

•Schmidek and Sweet. Operative Neurosurgical Techniques. 3rd edition.

•http://www.wheelessonline.com/ortho/dens_fracture

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