CT evaluation of Chamberlains, McGregors, and McRaes skull-base lines

AIM: To evaluate the mean distance from the odontoid process of C2 to the standard skull-base tines (Chamberlains, McGregors, and McRaes lines) on computed tomography (CT) imaging. To compare these measurements to previously documented plain radiograph and magnetic resonance imaging (MRI) measurements.MATERIALS AND METHODS: Reformatted midline sagittal CT images of 150 adults were retrospectively evaluated. The shortest perpendicular distance was measured from the Chamberlains, McGregors and McRaes baselines for each subject to the odontoid tip. Statistical analysis was performed to compare the CT data with the previously obtained MRI and plain film data.RESULTS: The mean position of the odontoid process was 1.4 mm below Chamberlains line (median 1.2 mm, SD 2.4 mm), 0.8 mm (median 0.9 mm, SD 3 mm) below McGregors line and 5 mm (median 5 mm, SD 1.8 mm) below McRaes tine. There is no significant difference between mate and female results (p 0.05) or between these CT and previous MRI measurements (p 0.05).CONCLUSION: These results provide the mean and range of normal distance from the odontoid process to the most frequently used skull-base tines on the current population on CT. (C) 2008 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.