Odontoid process fracture

C2 develops from four ossification centres at birth, one for each neural arch, one for the body and one for the odontoid process. The odontoid process itself forms from two separate ossification centres that fuse in the midline by the 7 fetal month, but occasionally can persist as a vertical lucent cleft in the odontoid (Ogden 1984). A secondary ossification centre appears at the tip of the odontoid process between 3 and 6 years of age and fuses by 12 years. This can be mistaken for an avulsion fracture (Fig. 7.57). The body of C2 fuses with the odontoid process by 2-6 years leaving a fusion line or remnant of the cartilaginous synchondrosis until 11 years of age and may be confused with a fracture either on radiographs or CT (Fig. 7.58). Pseudofractures of the odontoid process can be produced by the Mach effect by overlapping of the teeth, the posterior arch of Cl, occiput or soft tissues such as the tongue (Fig. 7.59). The neural arches of C2 fuse posteriorly by 2-3 years of age and the body fuses with the neural arches by 3-6 years. Additional ossification centres may be found at the tips of the spinous... 

Fig. 7.58. Sagittal CT reconstruction. Almost fused synchondrosis between the body of C2 and the odontoid process simulating a fracture in an 11-year-old...

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