The pathogenesis of idiopathic scoliosis. Biplanar spinal asymmetry

TLDR

Idiopathic scoliosis arises when median‑plane asymmetry, such as flattening or reversal of thoracic kyphosis, superimposes on normal coronal and transverse asymmetries during growth, making biplanar asymmetry the essential lesion. Increased anterior vertebral height at the curve apex with posterior end‑plate irregularity characterizes this median‑plane asymmetry, suggesting idiopathic scoliosis is the reverse of Scheuermann’s disease.

Abstract

A clinical, cadaveric, biomechanical and radiological investigation of the pathogenesis of idiopathic scoliosis indicates that biplanar asymmetry is the essential lesion. Many normal children have coronal plane asymmetry (an inconsequential lateral curvature of the spine), and certainly all have vertebral body asymmetry in the transverse plane, but when median plane asymmetry (flattening or more usually reversal of the normal thoracic kyphosis at the apex of the scoliosis) is superimposed during growth, a progressive idiopathic scoliosis occurs. Idiopathic kyphoscoliosis cannot and does not exist, from the mildest cases in the community to the most severe cases in pathology museums. Median plane asymmetry is crucial for progression and the lateral profile of the spine must be carefully scrutinised. Increased anterior vertebral height at the apex of the curve with posterior end-plate irregularity characterises the median plane asymmetry and suggests that idiopathic scoliosis is the reverse of Scheuermann's disease.