EBM Consult

Chamberlain Line on Radiographic Image


  • The Chamberlain line is drawn from the posterior surface of the hard palate to the tip of the opisthion (posterior aspect of the foramen magnum).
  •  It is used to measure the distance of how much the odontoid tip extends above this line.  If the tip of the dens extends > 3 mm above this line then it helps to recognize the presence of basilar invagination (a craniocervical junction abnormality where the tip of the dens project up into the foramen magnum).

Chamberlain's Line

    Radiographic (X-ray) Image

    Chamberlain Line 

    When the opisthion (posterior aspect of the foramen magnum) cannot be identified on a plain radiograph use the McGregor line.

    Related Content

    To see other related content please select an item below:


    McRae Line        Lateral X-Ray      Odontoid View


    1. Kwong Y et al.  AJR Am J Roentgenol 2011;196(4):W421-5. PubMed 
    2. Cronin CG et al. Clin Radiol 2009;64(1):64-9. PubMed


    Editors & Reviewers

    Editors:  Anthony J. Busti, MD, PharmD, FNLA, FAHA
    Last Updated:  June 2015