title: MR morphology of alar ligaments and occipitoatlantoaxial joints: study in 50 asymptomatic subjects.
abstract: OBJECTIVE
  To assess the magnetic resonance (MR) imaging appearance of the alar ligaments and joints in the upper cervical spine to determine the prevalence of structural alterations in asymptomatic individuals.
  
  
  METHODS
  Fifty healthy individuals (31 men, 19 women) with a mean age of 30 years (range, 19-47 years) underwent coronal T1- and T2-weighted and transverse T1-weighted MR imaging. MR findings were analyzed independently by two musculoskeletal radiologists, with disagreements resolved in conference.
  
  
  RESULTS
  Alar ligaments were detected in 42 (84%) (left side) and 38 (76%) (right side) of 50 individuals. The majority of ligaments (88%) and joints (58%) of the craniocervical junction (CCJ) were asymmetric. Asymmetry of the joint between C1 and C2 was less frequent (46%). Small amounts of fluid were detected in 8% of CCJ joints and 56% of C1-C2 joints in asymptomatic individuals.
  
  
  CONCLUSIONS
  Asymmetry of alar ligaments, CCJ and C1-C2 facet joints, and joint effusions are common in asymptomatic individuals. The clinical relevance of these MR findings is therefore limited in the identification of the source of neck pain in symptomatic patients.
authors.affiliation: Department of Radiology, Orthopedic University Hospital, Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. pfirrm16@centralnet.ch
authors.forename: C W
authors.initials: CW
authors.lastname: Pfirrmann
authors.forename: C A
authors.initials: CA
authors.lastname: Binkert
authors.forename: M
authors.initials: M
authors.lastname: Zanetti
authors.forename: N
authors.initials: N
authors.lastname: Boos
authors.forename: J
authors.initials: J
authors.lastname: Hodler
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology*; D001269:Atlanto-Occipital Joint / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged