34 years old female after car accident

History
34 years old female after car accident as front-seat passenger. The vehicle was overturning several times after tumbling down a scarp with 140 km/h. She complains about paresthesia of the right index and middle finger.

Imaging findings
Axial CT scans of the cervical spine show a fracture of the right articular process of C7 with communition (A). The right pedicle and the lamina are intact (B). Sagittal (C) and coronary (D) reformats show that the fracture has a vertical orientation and involves the superior facet joint. The volume rendering technique (E) of a CT angiogram performed after detection of the injury illustrates the topography between the fracture and the vertebral artery and confirms patency of this vessel. The MRI scan (inversion recovery pulse sequence, F) indicates disruption of the anterior and posterior longitudinal ligaments and distorsion of the interspinous ligaments at C6/7.

Diagnosis
Isolated fracture of the right articular process of C7 (also known as pillar fracture) with ligamentous instability and clinical evidence of right-sided C7 radiculopathy.

Discussion
Accounting for up to 10% of cervical spine injuries, pillar fractures are uncommon and most frequently affect C6 or C7. They are a result of simultaneous hyperextension and lateral tilting, producing axial loading on the side of rotation. The fracture, which typically has an oblique or vertical orientation, may be restricted to the pillar or may extend into adjacent structures including the facet joints, transverse foramina, pedicles, and laminae. Fractures involving both pedicle and lamina are termed pedicolaminar separation injury because they result in separation and displacement of a free-floating articular pillar fragment (pedicolaminar separation). Injuries without pediculolaminar separation are termed isolated pillar fractures. Radiculopathy without spinal cord damage is a common clinical feature and is more frequent when the superior facet joint is involved. Patients with pedicolaminar separation have a higher prevalence of neurologic deficits.

Image G shows a different patient with pillar fracture with pedicolaminar separation injury from a motorcycle accident. There is traumatic isolation of the left articular process of C4 with subluxation in the facet joint (arrow) and anteposition of C4 over C5. Moreover, there is left pillar fracture of C5 resulting from axial load impressing the left articular process of C4 into the left articular process of C5 (arrow head).

Pillar fracture with pedicolaminar separation

Pillar fracture with pedicolaminar separation

Pedicolaminar separation is a mechanically unstable injury, often requiring surgical fixation. Mechanical instability may also occur with an isolated pillar fracture as a result of injury to the anterior and posterior longitudinal ligaments, interspinous ligament, and facet capsule.

Pillar fractures are often poorly visualized at radiography. CT is the modality of choice for identifying the fracture, determining fracture extension into adjacent structures, and assessing for the presence of pedicolaminar separation. To evaluate ligamentous integrity MRI should be performed in pillar fractures.

Recommended reading
Rao et al.
Spectrum of Imaging Findings in Hyperextension Injuries of the Neck
Radiographics (2005) 25(5):1239

provided by Tim

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