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Neuroradiology Case of the Week
Case 278
Lawrence Swanson and P-L Westesson, MD, PhD, DDS
Clinical
Presentation: An 18-year-old male presented
with neck tenderness and tingling in the right hand after being involved in a high speed motor vehicle collision in which he was ejected from the automobile.
Imaging Findings: Sagittal CT through the cervical spine demonstrates a well corticated defect through the C6-C7 facet with associated jumped facet at C6-C7. Axial CT at this level reveals left-sided fracture.
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Figure 1: Sagittal CT of cervical spine revealing anterior dislocation of C6 relative to C7
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| Figure 2: Axial CT of cervical spine with left-sided fracture |
Diagnosis: Jumped facet (at C6-C7) and fracture (C6 facet)
Discussion: Between 12 and 16% of cervical spine injuries are unilateral facet dislocations and fracture-dislocations. A jumped facet occurs when the inferior facet becomes disarticulated with the superior facet, and is dislocated superiorly or anteriorly to the superior facet. In injuries where the inferior facet is forced anterior to the superior facet, the dislocation is called a locked facet. Forced hyperflexion or rotation, most frequently in the cervical spine, causes the dislocation. Research has produced varying opinions as to whether flexion or rotation is primarily responsible for the injury.
Clinical presentation of a jumped facet most commonly includes severe neck pain. Neurological abnormalities may be associated with the condition. In many cases, the patient is a recent victim of major trauma.
Diagnosis of a jumped facet can be made based on lateral cervical spine radiographs demonstrating anterior subluxation of one vertebral body on another. Imaging also proves useful when ruling out the fractures of the differential diagnosis, including whiplash fractures and rotatory extension fractures. Further imaging of a jumped facet, including MRI and CT, is commonly performed, and may be useful in gauging operative risk. However, the utility of imaging must be balanced against the benefit of immediate reduction, given the risk of neurological deficit due to prolonged compression of the spinal cord. Reduction methods can be either open or closed, and in some cases are followed by halo immobilization.
The prognosis depends on the degree of injury and the type and degree of neurological defect, if present. Many patients experience persistent neck pain, and some patients experience a repeat subluxation.
References:
- Hart RA. Cervical facet dislocation: when is magnetic resonance imaging indicated? Spine. 2002 Jan 1;27(1):116-7. [Medline]
- Vaccaro AR, Nachwalter RS. Is magnetic resonance imaging indicated before reduction of a unilateral cervical facet dislocation? Spine. 2002 Jan 1;27(1):117-8. [Medline]
- Beyer CA, Cabanela ME, Berquist TH. Unilateral facet dislocations and fracture-dislocations of the cervical spine. J Bone Joint Surg Br. 1991 Nov;73(6):977-81. [Medline]
- Crawford NR, Duggal N, Chamberlain RH, Park SC, Sonntag VK, Dickman CA. Unilateral cervical facet dislocation: injury mechanism and biomechanical consequences. Spine. 2002 Sep 1;27(17):1858-64; discussion 1864. [Medline]
- Ross: Diagnostic Imaging: Spine, 1st ed., Elsevier, 2004.
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