title: Morphometric and qualitative analysis of congenital occipitocervical instability in children: implications for patients with Down syndrome.
abstract: OBJECTIVE
  Congenital occipitocervical (OC) instability is uncommon in healthy children but can occur in many children with Down syndrome. A simple morphometric method of evaluating the OC joint in children with OC instability is presented, supported by a qualitative image analysis based on computed tomography (CT).
  
  
  METHODS
  Thin-cut CT scans of the OC joint were obtained in eight patients with Down syndrome and one patient with congenital OC instability. These patients' CT scans were compared with those of 15 healthy age-matched control individuals. Morphometric analysis was performed by measuring the depth and length of the superior articular surface (SAS) of C-1, and these values were normalized for a comparison between groups. Qualitative data were acquired using a surface-rendering technique for a visual comparison of the C-1 SAS. Morphometric analysis demonstrated an absence of the concave C-1 SAS anatomy in patients with congenital OC instability compared with age-matched control individuals (0.083 compared with 0.202, p < 0.001). Three-dimensional (3D) image analysis of the C-l SAS supported this finding.
  
  
  CONCLUSIONS
  Congenital differences in the shape of the OC joint are highly associated with atraumatic OC instability in children with Down syndrome. High-resolution CT imaging combined with 3D rendering techniques and surface mapping provides support for this assessment. It appears that abnormal OC joint shape is a contributing factor to congenital OC instability, especially in patients with Down syndrome.
authors.affiliation: Department of Neurosurgery, Division of Pediatric Neurosurgery, University of Utah, Primary Children's Medical Center, University of Utah, Salt Lake City, 84113, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Browd
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: Healy
authors.forename: Ginger
authors.initials: G
authors.lastname: Dobie
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Johnson
authors.forename: Greg M
authors.initials: GM
authors.lastname: Jones
authors.forename: Luis F
authors.initials: LF
authors.lastname: Rodriguez
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Brockmeyer
mesh_terms: D000293:Adolescent; D000886:Anthropometry; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000473:pathology*; D016022:Case-Control Studies; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000151:congenital* / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D014057:Tomography, X-Ray Computed