[FIGURES 5-6 OMITTED]
Atlas Fractures. Burst fractures of the [C.sub.1] ring can occur in children, just as in adults. The fracture may occur through the synchondroses, which may remain unfused until age 7. (64) CT Scan may assist in securing the diagnosis.
Atlantoaxial Injuries. Authors differ over the relative frequency of transverse ligament injuries compared to dens fractures. Although fractures through the base of the dens do occur at the synchondrosis, transverse ligament tears also are commonly seen. An atlantodens interval of 5 mm may suggest injury to the transverse ligament.
Surprisingly, children with dens fractures frequently are neurologically intact upon presentation. One series quotes seven of 15 children without weakness on presentation. Four of 15 had Thoracic level symptoms, and three had low Cervical symptoms ([C.sub.6] and [C.sub.7]). (65) Thirteen of the 15 had Anterior displacement ranging from 10-100% (mean 40%). One patient had a fracture, [C.sub.2] Tetraplegia, and no displacement of the dens. Two patients with 20% displacement had a delay in diagnosis of four and six months. Tomograms may show widening of the growth plate not evident on plain radiographs. (7) CT scans require coronal and sagittal plane reconstruction because axial scanning may miss fractures. (66,67) As the growth plates close, it is important not to confuse the epiphyseal scar at the base of the dens with an acute fracture.
Os Odontoideum. Os odontoideum refers to an oval or round ossicle of variable size with a smooth cortical border located in the position of the odontoid process. Authors differ, but suspect that this is an acquired Lesion after an undiagnosed odontoid fracture. These lesions commonly are unstable. (68,69)
Hangman's Fracture. Hangman's fracture, or [C.sub.2] pedicle fractures, can occur in children with a hyperextension injury, just as with adults. (See Figure 7.) The diagnosis of a hangman's fracture may be confused with physiologic Subluxation of [C.sub.2] on [C.sub.3]. Evaluating the alignment of the Posterior laminar line can assist with clarifying the diagnosis.
[FIGURE 7 OMITTED]
Atlantoaxial Rotary Subluxation. Atlantoaxial rotary subluxation may occur spontaneously (Grisel's syndrome) or after minor trauma. The classic clinical presentation is torticollis in the "cock-robin" position, with the head rotated to one side and tilted to the other, like a bird listening for a worm. (70) This usually stable injury is truly a pediatric injury, as up to 80% of these injuries occur in children younger than 13 years of age. (71,72) This type of rotary subluxation occurs most frequently at the [C.sub.1]-[C.sub.2] joint, where most of the rotation of the neck occurs. The facets are flatter at this joint than at any other joint.
The diagnosis of rotary subluxation is difficult to secure with plain films alone. The abnormalities seen can be present in patients with torticollis not due to subluxation and in volunteers holding their head in the "cock-robin" position. (7,73,74) CT scanning, with 3D reconstruction, often is necessary to make the diagnosis.
