Ossification of the dens is not complete until 6-8 years of age. The dens is formed by union of two lateral globular masses, achieving a conical shape at an age of viability. (1) This ossified dens retains a cartilaginous association with the body of [C.sub.2] until fusion occurs at age 6-8 years. The tip of the dens is formed by a separate ossification center. The superior portion of the dens is calcified by age 4 years.
In the newborn Cervical spine, the facet joints are flatter than those in the mature teenage spine, therefore, Anterior-Posterior relative motion is not limited in the newborn's cervical spine as well as it is in the mature spine. One study found that the facet joint angle does not assume an adult angle until age 10 years. (2) Additionally, potential voluntary anterior-posterior motion of one vertebral body upon another is increased until age 12 years.
Although no biomechanical data exist to quantify the difference, the musculature supporting the pediatric cervical spine is assumed to be laxer than in adults. In addition to a weaker neck, infants have a relatively larger head, per body weight, than adults do. In summary, in young children, a weaker neck that has less restriction to mechanical motion must support a heavier head. Being at an anatomic disadvantage, the cervical spine in infants and children may be at risk for injury at lower impact energies than would cause injury in adults.
Cervical Spine Malformations and Anomalies. As described above, embryologic formation of the vertebral column starts during the third to fourth week of gestation. Additionally, the major structures of the face and neck develop between weeks 4 and 12. (3) Children who have abnormal embryologic development of facial or neck features are at risk for abnormal cervical spine development as embryologic development of these two structures occurs simultaneously. (4) See Table 2 for a list of associated abnormalities. While the emergency physician often will not be able to identify the specific malformation syndrome, patients with face and neck anomalies should be considered at risk of having a congenitally abnormal cervical spine.
When examining cervical spine radiographs, it is necessary to look for any signs of congenital abnormality. Fusion of adjacent posterior elements commonly is associated with fusion of the vertebral bodies. Identification of the posterior fusion will appear earlier, as the complete ossification of the vertebral bodies is delayed in children. Fusions are most common above [C.sub.4], yet can occur throughout the cervical spine. Other common abnormalities include occiptoatlantal fusion, hypoplastic or anomalous portions of the atlas, ligamentous laxity, and malformations of the dens. (3,5)
Studies of U.S. football players have demonstrated that congenital cervical stenosis commonly is detected in athletes with transient neuropraxias. However, this anomaly does not predispose athletes to catastrophic neurological injury. (6)
