We investigate the hypothesis that normal spinal shape is genetically determined raising the possibility that individuals with scoliosis may inherit an ‘at risk’ spinal shape leading to the clustering of scoliosis within families.

A large scale study of spinal topography (Quantec system) in straight-backed sibling pairs of schoolchildren was undertaken. All children had no family or past history of spinal pathology and passed a modified Adams forward bend test. 223 sibling pairs were scanned including 28 heterozygote and 11 homozygote pairs. Control groups were constructed by breaking the sibling pair and replacing the removed sibling with an age, sex matched, unrelated counterpart. A sagittal spine line was extracted and analysed using principal component analysis to produce four scores accounting for 97.5% of the cumulative variation in shape. The scores were analysed by intraclass correlation coefficients (ICC).

The results for the second score were:-

All sibling groups showed greater correlation of sagittal profile for the second principal component than unrelated controls. Significant correlations in shape were seen for both twin groups where no correlation was seen with controls. A significant correlation was observed in same sex pairings. This work suggests that some elements of spinal profile may be familial but also shows correlation with sex. Both of these observations may be important in the aetiology of idiopathic scoliosis.