CT evaluation of Chamberlain's, McGregor's, and McRae's skull-base lines

AimTo evaluate the mean distance from the odontoid process of C2 to the standard skull-base lines (Chamberlain's, McGregor's, and McRae's lines) on computed tomography (CT) imaging. To compare these measurements to previously documented plain radiograph and magnetic resonance imaging (MRI) measurements.Materials and methodsReformatted midline sagittal CT images of 150 adults were retrospectively evaluated. The shortest perpendicular distance was measured from the Chamberlain's, McGregor's and McRae's 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.ResultsThe mean position of the odontoid process was 1.4 mm below Chamberlain's line (median 1.2 mm, SD 2.4 mm), 0.8 mm (median 0.9 mm, SD 3 mm) below McGregor's line and 5 mm (median 5 mm, SD 1.8 mm) below McRae's line. There is no significant difference between male and female results (p > 0.05) or between these CT and previous MRI measurements (p > 0.05).ConclusionThese results provide the mean and range of normal distance from the odontoid process to the most frequently used skull-base lines on the current population on CT.