The Dens: Normal Development, Developmental Variants and Anomalies, and Traumatic Injuries

Area of Science:

• Radiology
• Orthopedics
• Pediatrics

Background:

• Cervical spine imaging interpretation is challenging in pediatric and elderly populations.
• The craniocervical junction is susceptible to injury due to pediatric spine biomechanics and age-related degenerative changes.
• Congenital anomalies of the axis/dens are common and require differentiation from traumatic injuries.

Purpose of the Study:

• To provide a framework for interpreting cervical spine imaging, focusing on the dens.
• To cover normal dens development, ossification, and common congenital variants.
• To aid in distinguishing normal anatomy, variants, and anomalies from acute traumatic injuries.

Main Methods:

• Review of normal dens development and ossification.
• Description of common congenital variants (os odontoideum, persistent ossiculum terminale) and their imaging appearances.
• Discussion of fracture classifications, imaging features, and treatment options for the dens.

Main Results:

• Accurate assessment requires understanding normal developmental anatomy and its variations.
• Key imaging features help differentiate traumatic fractures from normal or variant anatomy.
• Os odontoideum and persistent ossiculum terminale are common congenital variations of the dens.

Conclusions:

• A foundational understanding of dens development and variants is essential for accurate cervical spine imaging interpretation.
• Radiologists must differentiate between congenital anomalies and acute traumatic injuries in the craniocervical region.
• This review provides essential knowledge for evaluating pediatric and elderly patients with potential cervical spine injuries.