- Anatomy:
- Body:
- one center (occassionally 2) appears by the fifth fetal month;
- Neural Arches:
- appear bilaterally by the 7 th fetal month
- fuse posteriorly by the 2nd or 3 rd year;
- Bifid tip of the Spinous Process
- occassionally a secondary center is present in each tip
- Neurocentral synchondrosis;
- fuses at 3 to 6 years;
- Inferior Epiphyseal Ring:
- appears at puberty and fuses at approximately 25 years;
- Summit ossification center for odontoid
- appears at 3 to 6 years and fuses with the odontoid by 12 years;
- basilar synchondrosis fuses by age 7 years, on average;
- subdental synchondrosis scar may remain as a remnant of this fusion;
- Odontoid (dens)
- two separate centers appear by the fifth fetal month and fuse w/ each other by the 7 th fetal month;
- Synchondrosis between odontoid and neural arch:
- fuses at 3 to 6 years;
- Synchondrosis between odontoid and body;
- fuses at 3 to 6 years;
- Congenital Anomalies of the Odontoid
- anomalies of the odontoid include complete aplasia, hypoplasia, and os odontoideum;
- hypoplasia of odontoid may be seen in conjunction w/ dysmorphic conditions such as achondroplasia or spondyloepiphyseal dysplasia;
- os odontoideum, the most common anomaly, occurs on both congenital and traumatic basis;
- all three conditions can produce symptoms and serious neurologic sequelae as a result of atlantoaxial instability