Go Back Spine/31. Cervical Spine/Trauma/31.4 - C1-2 Vertical Distraction Injury/ Go to Index

Horizontal and rotatory subluxation of the C1-C2 articulation is well described

Little information exists describing C1-2 vertical subluxation

No quantitative description of the normal relationship between the lateral masses of C1 and C2 in the vertical plane

Evaluation of craniocervical junction concentrated on assessing the integrity of the atlanto-occipital articulation and atlanto-dens interval.

(1) To define the normal relationship of the C1 and C2 lateral masses in the vertical plane

(2) To establish radiological criteria for the identification of C1-C2 vertical distraction injury by computed tomography (CT)

(3) To discuss the plain film, CT, and MR imaging findings in 6 patients with C1-C2 vertical distraction injuries.

Patient population

93 consecutive patients undergoing intracranial computed tomographic angiography (CTA) during a four-month study period composed the control group

All patients with a history of trauma were excluded.

All CT examinations were performed on a GE Lightspeed Plus Scanner

Helical scanning with 250-350 mA and 120 kVp with a 0.8 second scan

1.25 mm helically acquired axial images were reconstructed in an edge enhanced bone algorithm to a thickness of 0.65 mm

Reconstructions were performed in the coronal and sagittal planes (thickness of 2-mm at 2-mm intervals)

All measurements were performed on a DR systems workstation.

Coronal images were magnified and the C1-C2 junction was qualitatively evaluated

The image depicting the narrowest segment of the C1-C2 joint space was identified

The widest distance between the lateral masses of C1 and C2 was measured in a plane perpendicular to the joint space

C1-C2 lateral mass interval (LMI).

Three measurements were performed in each subject

Average left and right LMI values were calculated for each subject and for the group.

Sagittal images of the skull base were similarly magnified

Visually inspected to identify the image depicting the narrowest distance between the basion and the odontoid

basion-dens interval (BDI)

Three measurements performed in each subject

Average BDI was calculated.

Ninety-three patients were included in the control group

2-95 years (average age 54.7 years; 49 males, 44 females)

Average BDI -- 4.7 mm

standard deviation = 1.7; range 0.6 – 9.0 mm

Average Right C1-C2 LMI -- 1.6 mm

0.5; 0.8 – 3.3 mm

Average Left C1-C2 LMI -- 1.6 mm

0.5; 0.7 – 3.1 mm

No correlation was observed between patient age and either BDI or LMI.

9 of 186 cases “elliptically” shaped joint space

average LMI of the elliptically shaped C1-C2 joint spaces (n=9) was 2.6 mm (standard deviation 0.42 mm; range 2.1 –3.3)

significantly wider than the average LMI of the linear or “cup-shaped” group (p < 0.05)

177 of 186 cases linear or “cup-shaped” appearance to the articulation.

Clinical information was reviewed from 6 patients

5 male, 1 female

mean age 29 years, range 6-40 years

Imaging:

Conventional radiographs (n=6)

CT (n=5)

MR imaging (n=5).

CT examinations were performed on a GE Lightspeed Plus scanner

120 kV and 200-300 mA (1.0 second scan)

Helically acquired axial with 2.5 mm collimation at a 1:1 pitch (HQ) reformatted to a thickness of 1.25 mm at 0.75 mm intervals

Reconstructed using an edge-enhanced algorithm

Sagittal and coronal reformations were performed with 2-mm collimation at 2-mm intervals.

Signa 1.5 T magnet (GE Medical Systems, Milwaukee WI).

Sequences included:

Sagittal T1 (TR 450 ms; TE 8 ms)

Sagittal FSE T2 (3500-5000; 100)

Sagittal and axial GRE (700, 17, flip angle 20)

Sagittal and coronal FSEIR (2500-2650; 40; TI 150; flip angle 90).

AP films

widening of the distance between the lateral masses of C1 and C2

visualization of the C1-C2 interspace

usually obscured by overlying osseous structures, extraneous objects, and support equipment.

Lateral Radiographs

Widening of the posterior elements

Obvious cases only

Uncovering of the posterior aspect of the anterior arch of C1

Not sensitive.

CT examinations were available in five of the six patients.

Average C1-C2 LMI -- 5.5 mm

Range: 3.3 mm – 9.4 mm

LMIs were significantly wider in the C1-C2 distraction injury group than in the control group (p < 0.001)

LMIs in all injured patients measured >3 standard deviations above the mean LMI established in the control group.

Most evident on coronal reconstructions

Also appreciated on the far lateral sagittal reconstructions.

Elliptical joint space

Lateral and medial aspects of lateral masses are close or in contact

Extremes of head position may physiologically widen the interspace

e.g. direct coronal sinus CT.

MR imaging (5 of 6 patients)

All patients demonstrated abnormally increased signal on FSEIR images distributed diffusely throughout the C1-C2 lateral mass articulation

Most evident on coronal STIR images

Less conspicuous on sagittal STIR

Easily missed on sagittal FSE T2 images.

ENT Neck FSEIR sequences evaluated

Relatively isointense signal

Similar to facet articulations and non-degenerated discs.

MR imaging functions to confirm CT findings

Diffusely increased signal throughout the joint space as brite as CSF

Brighter than the intervertebral discs and facet articulations.

Not reported in radiological literature

Patients have undergone significant trauma and subsequent films are frequently technically limited

Overlying equipment, osseous structures

Suboptimal patient positioning

Distracting findings

No normative data.

Difficult to qualitatively identify

Not in typical radiological search pattern

“the eye sees what the mind knows”

Bilaterally symmetric

No established normal distance

Minimal findings in axial plane

Many centers do not routinely perform coronal and sagittal reformations.

Inconspicuous if no FSEIR/STIR sequences included.

Plain Films

Lateral:

uncovering of posterior aspect of anterior arch of C1

marked widening of the posterior elements

AP: wide C1-2 interspace

CT – diagnostic study

Appropriate mechanism

Neck pain

LMI > 2.6 mm

Not an elliptically shaped joint space

Patient not in hyperflexed or hyperextended position.

MR – confirmatory study

Coronal FSEIR/STIR images are optimal

Increased signal throughout joint space as bright as CSF

May be relatively inconspicuous on FSE T2.