Genetic predisposition is a key causal factor in adolescent idiopathic scoliosis (AIS), which is the most common form of spinal deformity. However, common quantitative genetic effect estimates such as hereditability have not been fully evaluated and reported for this disorder. We aimed to determine the sibling recurrent risk and hereditability of AIS in first-degree relatives of 513 Chinese patients with this disorder. Family members of 513 Chinese patients with AIS attending a scoliosis clinic were assessed. A diagnosis of AIS was made with the criteria of Cobb angle greater than 20°. The evaluation included clinical assessment and physical examination in a health screening centre by medical doctors with use of forward bending test. Any positive screening cases were referred to a scoliosis clinic for follow-up spinal radiograph. All radiographs were assessed by an orthopaedic surgeon in the scoliosis clinic. A population prevalence of scoliosis was obtained from the data of a territory-wide screening campaign. The prevalence of AIS among siblings of probands was measured both overall and divided by sex of siblings. The sibling recurrent risk (λs) was calculated for male and female siblings separately with reported population incidence of AIS.Introduction
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