Characterization of idiopathic scoliosis in a clinically well-defined population.

Idiopathic scoliosis is a highly prevalent disorder, familial in nature, with marked clinical variability. The purpose of this study was to characterize idiopathic scoliosis in a large series of families to be used for a genome-wide search. One hundred thirty-one multigenerational families (892 individuals) with at least two affected individuals were studied. Data obtained included curve pattern, treatment, and back pain. Maximum curvature as a continuous variable was evaluated using t tests for dichotomous characteristics and linear correlation for continuous variables. An analysis of familial loading was done. Four hundred forty-four individuals were classified as affected (82% female; 18% male). The right thoracic and left lumbar curves had the highest mean curvature (49 degrees). Mean curve size was greater in individuals with back pain. Back pain was most prevalent in the right thoracic and left lumbar curve pattern. The Pearson correlation coefficient between the number of affected family members and the maximum degree of curvature was 0.16, suggesting that the greater the lateral curvature, the higher the proportion of family members affected with scoliosis. The sample population is consistent with those of previous studies in relation to gender and curve size. Statistically, the familial nature of this disorder is supported.