Atlantoaxial Dislocation in a Child Secondary to a Displaced Chondrum Terminale
A Case Report
John Hammerstein, MD; Scott Russo, MD; Ken Easton, MD

Among children, cervical spinal injuries are rare. When they do occur, younger children sustain more upper cervical injuries than older children do1,2. The spinal anatomy of children (i.e., a disproportionately large head, wedge-shaped vertebrae, and horizontally oriented facets) is different than that of adults and offers little resistance to the high shear forces that predominate in falls and/or motor-vehicle accidents1-5.

Fig. 1

Lateral radiograph of the cervical spine, made on the day of injury, demonstrating atlantoaxial dislocation.

The tip of the odontoid process is not ossified at birth. The chondrum terminale is a cartilaginous epiphysis at its apex. Fusion of the terminale to the rest of the dens, if it happens at all, does not take place until a child is between ten and thirteen years of age. This physis is a potential weak spot at the C1-C2 junction.

The transverse ligament is the horizontal portion of the cruciate ligament and is the most important ligamentous structure of the C1-C2 complex of the occiput. It is the primary and most crucial stabilizing component of all of the ligaments of the atlantoaxial complex, confining the odontoid process within the articular notch on the anterior arch of C1 and preventing anterior subluxation of C1 on C2. The transverse ligament lies just below the physis of the chondrum terminale.

The nonelastic nature of the transverse ligament and its proximity to the physis of the chondrum terminale makes this area a potential site for pediatric cervical spinal injury. The following case outlines our hypothesis for a mechanism of injury that, to our knowledge, has not been reported previously. The family of our patient was informed that data concerning the case would be submitted for publication.

Fig. 2-A

T2-weighted sagittal magnetic resonance imaging scan of the upper portion of the …

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