Clinical predictors andradiological reliability in atlantoaxial subluxation inDown'ssyndrome

Clinical signs andsymptoms thatmight pre- dictatlantoaxial subluxation werestudied prospectively in135of180children with Down'ssyndrome aged6-14years whoform theHester Adrian Research Centre cohort. Lateral radiographs ofthecervical spine were takeninflexed, extended, andneutral posi- tions, andthepercentage ofabnormalities in eachviewwas14,10,and10%,respectively. Gaitwastheonlysignificant clinical predic- tor.Therelative risk ofhaving anabnormal neckradiograph withanabnormal gaitwas 2-91(95%confidence interval (CI) 1to8).The sensitivity was50%andthespecificity 81%. Nineteen children hadrepeat radiographs to assess thereliability ofradiological diagnosis. Sixhadabnormalities; five of19(26%) hadan abnormality onthefirst radiograph, andfour of19(21%)hadanabnormality onasecond radiograph, butonlythree(15%)hadan abnormality onbothoccasions inanyview (95%CI0to25). We conclude thatradiographs ofthecervi- calspine areunreliable atidentifying atlanto- axial subluxation inchildren withDown's syndrome, andwefailed toidentify anyreli- ableclinical predictor.