The study of development of new simulation system for corrective surgeries for spinal defurmity

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Various spinal instrumentation surgery for scoliosis have been carried out. However, since scoliosis is a three-dimensional deformity, it is frequently difficult to select an optimum surgery for a particular patient. The purpose of this study is to simulate surgical correction of scoliotic spine using a three-dimensional mathematical model having mechanical properties of the disc, the vertebral body, and the rib cage. Preoperative spinal shape was measured using bi-plane X-ray photogrammetry three-dimensionally. Material compensational coefficient of each patient was estimated by X-ray film taken under axial traction. Using this model, we simulated 23 corrective surgeries for scoliosis with average Cobb angle 52 degrees. Postoperative average Cobb angle was 28.5 degrees on conventional X-ray and 28.3 degrees by the simulation. The average difference of the two was 6.0 degrees. For kyphosis, 14.2 degrees on conventional X-ray and 19.2 degrees by the simulation. The average difference of two methods of measurement was 7.4 degrees. In axial rotation, postoperative rotation angle was 12.3 degrees using computed tomography and 9.7 degrees by the simulation. The average difference between two methods was 3.6 degrees. The corrective effect of the instrumentation surgery could be predicted three-dimensionally using our simulation model. The model was put to practical use for the instrumentation surgery.