title: Posterior occipitoatlantal hypermobility in Down syndrome: an analysis of 199 patients.
abstract: We endeavored to determine the prevalence of occipitoatlantal hypermobility in individuals with Down syndrome, to establish objective radiographic criteria for this entity, and to correlate this with neurologic abnormality. In a retrospective analysis, upper cervical spine radiographs of 210 patients with Down syndrome were compared with those of 102 normal individuals. Radiographs were evaluated using the Powers ratio. Patients identified with radiographic evidence of posterior occipitoatlantal hypermobility were then examined clinically and compared with a matched group of patients with Down syndrome and normal Powers ratios. Of the patients with Down syndrome, 8.5% had a Powers ratio of < 0.55, which was indicative of posterior occipitoatlantal hypermobility (POAH). Furthermore, 66% of those with an abnormal Powers ratio had positive neurologic findings upon physical exam, a finding that was statistically significant when compared to a matched group of patients with Down syndrome and normal Powers ratio.
authors.affiliation: Section of Orthopaedics, Medical College of Georgia, Augusta 30912-4030.
authors.forename: T A
authors.initials: TA
authors.lastname: Parfenchuck
authors.forename: S L
authors.initials: SL
authors.lastname: Bertrand
authors.forename: M J
authors.initials: MJ
authors.lastname: Powers
authors.forename: D M
authors.initials: DM
authors.lastname: Drvaric
authors.forename: S M
authors.initials: SM
authors.lastname: Pueschel
authors.forename: J M
authors.initials: JM
authors.lastname: Roberts
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies