Biomechanical Analysis Of Orthopaedics Of Three-dimensional Finite Element Model Of Idiopathic Thoracolumbar Scoliosis

Obiect: To investigate biomechanical effect of different corrective loads applied on the three-dimensional linear finite element model of idiopathic scoliosis. The corrective loads are divided into forces of distraction, compression, translation and rotation.Method: In the study, a detailed three-dimensional linear finite element model of an intact scoliotic thoracolumbar vertebral column was constructed with the geometrical data obtained from the CT images using a general purpose finite element software SuperSap93 and Superdraw99. Corpus vertebrae and arcus vertebrae were modeled using eight-noded brick elements. Using the material properties from literature, the 2885-finite element model was exercised under different corrective loads such as forces of distraction, compression and rotation, etc. The forces acted alone or together. As a logical step, a parametric study was conducted by evaluating the biomechanical response related to the changes in the model. The values of stress and displacement of all nodes were analysed with SSPS software to evaluate the function of different corrective loads.Results: Axial forces have less effect than horizontal ones in altering the angulation of the spine when the angulation is about 40 degrees. Distraction loads can not correct spinal rotatory deformity. Derotation can be achived by applying rotation forces. Improper distraction loads will lead to lumbar kyphosis. Compression forces applied on the convex side of the spine will increase the stress of the points on the concave side of the spine when the coronal deformity has not be corrected satisfactorily. The stress of the point shows direct ratio to the intensity of distraction force, so do the values of longitudinal displacement.Conclusions: Axial forces (distraction or compression) are an inefficient means of altering the shape of a curved spine unless the curve is considerable. When the angulation is about forty degrees, the horizontal corrective loads will acquire better effect than the longitudinal ones. Rotation deformity can only be corrected by the application of a horizontal force whose force line doesn't pass through the center of the spine. The compression loads should be applied to preserve the curve of the lumbar spine. The three-dimensional deformity of the spine will be corrected satisfactorily by the application of rational combination of different corrective loads. The study shows that three-dimensional finite element analysis can be an effective means applied to the selection of operative method of the idiopathic scoliosis.