Early Sagittal Shape of the Spine Predicts Scoliosis Development in a Syndromic (22q11.2DS) Population A Prospective Longitudinal Study

Background: Scoliosis is a deformation of the spine and trunk that, in its more severe forms, creates a life-long burden of disease and requires intensive treatment. For its most prevalent form, adolescent idiopathic scoliosis, no underlying condition can be defined, and the pathomechanism appears to be multifactorial; however, it has been suggested that the biomechanics of the spine play a role. For nonidiopathic scoliosis, underlying conditions can be recognized, but what drives the deformity remains unclear. In this study, we examined the early sagittal shape of the spine before the onset of scoliosis in a population with 22q11.2 deletion syndrome (22q11.2DS). This cohort was chosen since children with this syndrome have an approximately 50% chance of developing scoliosis that shares certain characteristics with idiopathic scoliosis, namely, age of onset, curve morphology, and rate of progression. Methods: This prospective cohort study included patients with 22q11.2DS who were followed with the use of spinal radiographs during adolescent growth. All of the children, who initially had no scoliosis while still skeletally immature (Risser stages 0 and 1), were followed at 2-year intervals until they reached skeletal maturity (Risser stages 3 to 5). We assessed the segment of the spine that has previously been shown to be rotationally unstable, the posteriorly inclined segment, to determine if it was predictive of later scoliosis development. For quantification, the area of the “posteriorly inclined triangle” (PIT), a previously described parameter that integrates both the inclination and length of the at-risk segment, was measured. Results: Of the 50 children who initially had no scoliosis (mean age at inclusion, 10.7 ± 1.7 years; mean follow-up, 4.8 ± 1.6 years), 24 (48%) developed scoliosis. Patients with an above-average PIT area (>60 cm²) at inclusion showed a relative risk of 2.55 for scoliosis development (95% confidence interval [CI]:1.22 to 5.34). PIT inclination was correlated with curve type: a taller and steeper hypotenuse predicted later thoracic scoliosis, while a shorter and less steep inclination predicted the development of (thoraco)lumbar scoliosis. Conclusions: This prospective study identified the pre-scoliotic sagittal shape of the spine as a risk factor for the later development of scoliosis in the population of children with 22q11.2DS.