Fig. 3

Progressive ossification of C2 vertebra: a: sagittal reconstructed CT image of the craniocervical junction of a 6-year-old male who fell 30 feet off a balcony—ossification has not yet begun in the chondrified apical dens (black arrow) in this 6-year old and the lower dental synchondrosis (white arrow) is also evident as non-ossified cartilage. C2-C3 pseudosubluxation is present.; b: volume-rendered three-dimensional reconstructed CT image of the C2 vertebra of the same 6-year-old male—the apical dens is non-ossified (arrow) and the ossified basal dental segment (outlined asterisk) and the body of the C2 vertebra (black asterisk) have not yet fused; c: sagittal reconstructed CT image of the craniocervical junction of a 5-year-old male who fell from a first floor window—ossification has begun but is incomplete in the chondrified apical dental segment (white arrow) and a thin ossifying lower dental synchondrosis (black arrow) is evident. The appearances should not be misinterpreted as fracture changes despite the high-energy clinical information apparent. C2-C3 pseudosubluxation is again present; d: volume-rendered three-dimensional reconstructed CT image of the C2 vertebra of the same 5-year-old male—the ossification of the apical dens is evolving (white arrow) and the lower dental synchondrosis is still visible (thin black arrow); f: sagittal reconstructed CT image of the craniocervical junction of a 6-year-old female who was a pedestrian struck by a car travelling at moderate speed—advanced ossification of the apical dental segment is present (black arrow) with early ossification across the upper synchondrosis (white arrow). Pseudosubluxation at the C2-C3 level is present; f: volume-rendered three-dimensional reconstructed CT image of the C2 vertebra of the same 6-year-old female—ossification across the upper synchondrosis (thin white arrow) and lower synchondrosis exhibits progressive features as union of the ossification centres proceeds