Radiographic morphology of normal ring apophyses in the immature cervical spine

The ring apophyses of the cervical spine have a variable appearance that changes with age. The times at which they appear and fuse at each level are not fixed. In this study, we aim to detail normal ranges of appearance of these ossification centers for each age group.

One hundred and eighty patients under the age of 21 attending the Royal Stoke University Hospital for cervical spine radiographs were retrospectively identified. The presence or absence of ring apophyses at each cervical level and whether these had undergone fusion was reported, as were the thickness, length, and craniocaudal and anteroposterior distance of the apophysis from the vertebral body. The angulation of the apophysis relative to the endplate was also noted.

The youngest patient in which apophyses were seen was aged 3, but apophyses were otherwise rarely seen before the age of 6. All apophyses were present from age 14, and the superior apophyses fused by the age of 18, although unfused inferior apophyses were still seen in the 20-year age group. It was observed that apophyses were rarely separated from the vertebral body by greater than 1 mm in craniocaudal distance (1%) or 2.5 mm in anteroposterior distance (2.6%) and the anterior apophysis was angulated towards the endplate in only 1% of cases.

We have detailed the range of normal appearances of the ring apophyses of the developing cervical spine. Cervical spine apophyseal injury is thought to be rare, but knowledge of normative morphological features should help in this diagnosis.