Reassessment of the craniocervical junction: normal values on CT

Area of Science:

• Radiology
• Anatomy
• Medical Imaging

Background:

• The standard of care for cervical spine evaluation is transitioning from plain radiographs to multidetector row CT (MDCT).
• Existing normal ranges for occipitovertebral articulations were established using plain radiography.
• A re-evaluation of normal craniocervical anatomy using MDCT is necessary.

Purpose of the Study:

• To define normal anatomic relationships of craniocervical articulations on MDCT.
• To identify discrepancies between MDCT-derived normal values and those from plain radiographs.

Main Methods:

• 200 patients underwent cervical spine MDCT with multiplanar reconstructions (MPR).
• Measurements included basion-axial interval (BAI), basion-dens interval (BDI), Powers ratio, atlantodental interval (ADI), and atlanto-occipital interval (AOI).
• Statistical analysis compared MDCT values to historical plain radiograph data.

Main Results:

• Ninety-five percent of the population had a BDI < 8.5 mm (vs. 12 mm on plain radiographs).
• Ninety-five percent had an ADI < 2 mm (vs. 3 mm on plain radiographs).
• The AOI ranged from 0.5 mm to 1.4 mm (95% population). The Powers ratio showed no significant difference.

Conclusions:

• Normal craniocervical relationships measured by MDCT differ significantly from plain radiograph values.
• Proposed new normal values for the adult population based on MDCT.
• BAI was found to be difficult to reproduce on CT images.