title: Craniometric measurements in the assessment of craniovertebral settling: are they still relevant in the age of cross-sectional imaging?
abstract: OBJECTIVE
  Craniovertebral settling is a serious complication of rheumatoid arthritis, and a number of radiographic measures at the craniocervical junction are in use to enable its diagnosis. However, these measures are hampered by the overlap of relevant bony landmarks. We aim to establish accurate values for these measures on CT to facilitate early diagnosis of this condition on cross-sectional imaging.
  
  
  METHODS
  One hundred men and 100 women who underwent CT that included imaging of the craniocervical junction were retrospectively identified. Patients between the ages of 18 and 49 years were included. Two radiologists reformatted the images in the midsagittal plane and performed a series of measurements as follows: the Wackenheim line, McRae line, Chamberlain line, and McGregor line and measurements obtained using the Redlund-Johnell method and our modification of the method proposed by Ranawat et al.
  
  
  RESULTS
  There were significant differences between the CT values and accepted radiographic measurements for the Wackenheim, Chamberlain, and McGregor lines. The McRae line was the easiest to measure, and the odontoid tip did not cross this line in any patient (distance from line: range, 0.6-10.4 mm). The CT measurements obtained using the Redlund-Johnell method were similar to the radiographic values, and we provide normal CT values for the modified Ranawat method (men > 23.7 mm, women > 24.2 mm).
  
  
  CONCLUSIONS
  We propose that the McRae line should be used over other methods when assessing for craniovertebral settling on cross-sectional studies because it is the easiest measure to understand and remember. If the odontoid tip is eroded, the Redlund-Johnell and modified Ranawat methods are alternatives, and we have provided normal CT values for those measures as well.
authors.affiliation: Department of Radiology, Nottingham University Hospitals, Hucknall Rd, Nottingham NG51PB, United Kingdom. dryune@hotmail.com
authors.forename: Yune
authors.initials: Y
authors.lastname: Kwong
authors.forename: Nitin
authors.initials: N
authors.lastname: Rao
authors.forename: Khalid
authors.initials: K
authors.lastname: Latief
mesh_terms: D000293:Adolescent; D000328:Adult; D001172:Arthritis, Rheumatoid / Q000150:complications* / Q000473:pathology; D001268:Atlanto-Axial Joint / Q000473:pathology*; D002508:Cephalometry / Q000379:methods*; D002574:Cervical Vertebrae / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods*