Growth curves of Dutch children with Down's syndrome.

Two thousand and forty-five observations on height and weight were collected from 295 healthy Dutch children with Down's syndrome. In a cross-sectional analysis, means and standard deviations were calculated per age-class, and subsequently smoothed, resulting in age references between 0 and 20 years. Each child contributed only once in every age class. In a subgroup in whom more than four measurements were available before puberty, quadratic regression functions were determined on the basis of the full data set, as well as for individual children separately (54 boys and 25 girls). The average coefficients of the individual regression functions were almost identical to the coefficients of the regression line through all data, indicating that the reference curve for the mean height based on cross-sectional analysis adequately represents longitudinal growth during childhood. Dutch children with Down's syndrome are taller than their US peers (P50 equals P75) but more than 2 SD shorter than normal Dutch children. Above the age of 10 years, the mean weight for height is above the P90 of normal children.

Radiological assessment of the atlantoaxial distance in Down's syndrome.

People with Down's syndrome are pre-disposed to atlantoaxial instability. As part of a study to determine whether those with Down's syndrome should be screened for atlantoaxial instability before they participate in sport, a series of 279 children, aged 6 to 17 years was investigated radiologically. Lateral radiographs of the cervical spine were taken in neutral position and in flexion. The magnification factor was assessed by means of a marker attached to the nape of the neck. After correction for magnification 15% of the patients were found to have an atlantoaxial distance greater than 4 mm on the flexion film, especially boys under 11 years of age. However, sex and age together explained at most 9% of the variation in atlantoaxial distance. The maximum distance found was 6.5 mm. The disagreement between the means of first and second measurements by the same (test-retest) and by another (inter-) observer was more for those taken in the neutral position than in flexion. On a group level the results for reliability were satisfactory.

Risk of sports activities in children with Down's syndrome and atlantoaxial instability.

10-40% of children with Down's syndrome have atlantoaxial instability. These children might run the risk of spinal cord compression if they play sport. The aim of our study was to assess this presumed risk. We obtained 282 radiographs of the cervical spine from a cohort of 400 children and young adults with Down's syndrome who attended special schools and who were between 4 and 20 years old (about 25% of all such children in the Netherlands). The atlantoaxial distance was more than 4 mm in 91 children. These children were randomly assigned to two groups, with the provision that all children at any particular school were assigned to the same group. Children of one group were allowed to continue their habitual sports and exercise activities, whereas those in the other group were advised not to play "risky" sports (as defined by a panel of four experts) and not to make "risky" movements during physical education lessons. The compliance of the experimental group was good. After a year, there were no differences between the groups in scores on a functional motor scale, the frequency of neurological signs, or changes in the atlantoaxial distance. The motor function of a third group of 44 children with Down's syndrome but normal atlantoaxial distances was similar to that of children in the other two groups, as was the frequency of neurological signs. These findings suggest there is no reason to stop children with Down's syndrome from playing certain sports and no need to screen them by radiography before they take up such sports activities.

No relation between general laxity and atlantoaxial instability in children with Down syndrome.

Atlantoaxial instability in children with Down syndrome (DS) may be caused by laxity of the transverse ligament. We tested the hypothesis that general laxity might predict atlantoaxial instability. General laxity and the atlantoaxial distance were assessed in 172 children with DS (aged 6-17 years; 45% girls, 55% boys). No significant correlation was noted between these two measures with either univariate or multivariate methods of statistical analysis.