In vivo quantitative analysis of scoliotic vertebrae

An in vivo method based on CT images and finite element meshing had been developed to quantify and visualize the bone density distribution of scoliotic vertebrae. CT examination (axial acquisition of the apical, superior and inferior adjacent vertebral bodies) had been performed on seven girls presenting an idiopathic scoliosis. Using an in-house image processing software and the pre-post processor Patran, a surfacic finite element mesh of each body slice was proposed allowing an automatic mapping of the cancellous bone slices and a volumic mesh for the bone density distribution visualization. In the coronal plane, compared to the body geometrical centre, the body mechanical centre was shifted forward in the concavity of the curvature for six patients and in the convexity for one patient. For each patient, this shift forward was made in a same way for the three vertebrae. In the sagittal plane, the body mechanical inertia centre was shifted forward in the posterior side for 12 vertebrae, in the anterior side for 3 vertebrae and was not shifted forward for 6 vertebrae. This shift forward was made in the anterior side for the inferior adjacent vertebra. The shift forward by slice was made in a same way for each slice, excepted at the end plates. Besides, one can observe that the scoliotic deformation evolution seemed to modify the mechanical property distribution. The results may also suggest predictive criteria of evolution of the scoliotic deformities.