Traumatic rupture of the neurocentral synchondrosis of the axis in a child.

The authors report the first case of unilateral traumatic rupture of the C-2 neurocentral synchondrosis. A 26-month-old child was in a vehicular collision that caused his head to be rotated sharply to the left with the neck flexed. He had severe neck pain but was neurologically normal. Computerized tomography scanning showed rupture of the left C-2 neurocentral synchondrosis, a right C-2 pars interarticularis fracture, and anterior angulation of C-2 on C-3. The neck injury was unrecognized until postinjury Day 9 when an MRI study showed a tear of the posterior longitudinal ligament at C2-3 and separation of the C-2 body from the inferior anular epiphysis. A second CT showed widening of the synchondrosis fracture, increased angulation of C-2 on C-3, and distraction of the right C-2 pars fracture. The mechanism of the neurocentral synchondrosis fracture is thought to be hyperflexion-axial loading combined with leftward rotation, which provided the lateral force that overcame the cartilaginous synchondrosis and extruded the lateral mass. The patient underwent open reduction and posterior fusion of C1-3, and was maintained in a halo jacket for 4 months, when CT scans demonstrated solid C1-C3 fusion and ossification of the injured synchondrosis. Unilateral traumatic rupture of the C-2 neurocentral synchondrosis is one component of several injuries involving C-2 sustained before synchondrosis closure. The resulting C2-3 relationship is highly unstable. Reduction and C1-C3 fusion are necessary in patients with significant displacement of the adjacent bony units.