title: Synovial folds of the lateral atlantoaxial joints: in vivo quantitative assessment using magnetic resonance imaging in healthy volunteers.
abstract: METHODS
  Analysis of magnetic resonance (MR) images of healthy volunteers.
  
  
  OBJECTIVE
  To develop and validate an imaging protocol and measurement technique to describe the morphology and quantify the dimensions of the synovial folds of the lateral atlantoaxial joints in vivo.
  
  
  BACKGROUND
  The synovial folds of the lateral atlantoaxial joints are considered to be a potential source of neck pain and headache, especially following whiplash injury. Until recently, it has not been possible to image the synovial folds in vivo and consequently their normal morphology is not fully understood.
  
  
  METHODS
  MR images of the cervical spine of 17 volunteers (4 male and 13 female) were acquired using a 1.5-tesla scanner. The morphology of the synovial folds at the lateral atlantoaxial joints was described and their presence determined. The volume and cross-sectional area of the ventral and dorsal synovial folds of the right and left lateral atlantoaxial joints were measured and compared. The relationship between the dimensions of the synovial folds and subject age was examined. Twenty synovial folds were measured twice by one observer and once by a second observer for the determination of measurement reliability.
  
  
  RESULTS
  There was a significant difference in volume (chi [3] = 17.54, P = 0.000) and cross-sectional area (chi [3] = 18.95, P = 0.000) between the ventral and dorsal synovial folds of the left and right lateral atlantoaxial joints. There was no correlation between synovial fold dimensions and age. The reliability of the measurements ranged from intraclass correlation coefficient 0.95 to 0.99 (intraobserver reliability) and intraclass correlation coefficients 0.75 to 0.82 (interobserver reliability).
  
  
  CONCLUSIONS
  MR imaging was successfully implemented as a noninvasive method for visualizing the synovial folds of the lateral atlantoaxial joints and quantifying their dimensions in healthy volunteers. The results of this study provide a basis for future studies investigating synovial fold pathology in patients with neck pain and headache.
authors.affiliation: Centre for Learning Anatomical Sciences, University of Southampton, United Kingdom. A.L.Webb@southampton.ac.uk
authors.forename: Alexandra L
authors.initials: AL
authors.lastname: Webb
authors.forename: Angela A
authors.initials: AA
authors.lastname: Darekar
authors.forename: Madeline
authors.initials: M
authors.lastname: Sampson
authors.forename: Hamid
authors.initials: H
authors.lastname: Rassoulian
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology*; D002574:Cervical Vertebrae / Q000033:anatomy & histology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D013583:Synovial Membrane / Q000033:anatomy & histology*; D055815:Young Adult