Etiology of idiopathic scoliosis. Computational study.

A review of the literature on the mechanical aspects of the etiology for idiopathic scoliosis reveals that the buckling hypothesis has been presented as a purely mechanical phenomenon. In an attempt to confirm the buckling hypothesis, a numerical simulation of growth and the resulting buckling phenomena was done by means of finite element analysis. It previously was observed that growth was induced in the T4 to T10 vertebrae. Only the sacrum was assumed to be stationary. From the growth analysis, a deformation process that mitigated thoracic kyphosis was obtained as observed in healthy children during early adolescence. From the buckling analysis, the first to the fourth buckling modes that correspond to the first side bending, first forward bending, first rotation, and second side bending modes were obtained. The shape of the fourth buckling mode (second side bending mode) was in good agreement with the clinical shape. Considering the potential for controlling these modes by posture change, it is concluded that the second bending mode in the coronal plane is one of the most likely etiologic candidates in the mechanics of thoracic idiopathic scoliosis.