Sagittal spinal flexibility in patients with idiopathic scoliosis.

To determine whether or not reduced sagittal spinal flexibility is associated with idiopathic scoliosis we measured the sagittal spinal flexibility in 40 normal children and in 93 children with idiopathic scoliosis. Sagittal spinal flexibility, or the range of spinal flexion (RSF), was calculated from lateral radiograms of each spine by measuring the difference in the segmental kyphotic angle between the neutral standing position and the maximally flexed position. The spines of all 40 normal children bent smoothly, but 87 of the 93 scoliosis patients had localized areas of severely decreased RSF. This striking difference in sagittal spinal flexibility between normal children and patients with idiopathic scoliosis suggested that a loss in spinal flexibility in the sagittal plane was associated with idiopathic scoliosis, and may contribute to the pathogenesis and progression of spinal curvature.