Biomechanical simulations of scoliotic spinal deformity and correction.

A new approach to surgical correction of scoliosis has been advanced by us, in the form of simulation of the surgical correction system and technique. For this purpose, we developed a finite-element model of the spinal column (SFEM), applied tractions to it and determined the model stiffness so as to watch the actual spinal geometry. Having patient-simulated this SFEM, we applied to this SFEM corrective forces and determined the optimal set of forces to gain the best correction of the spinal deformity. We then developed a special instrumentation to measure the applied corrective forces during surgery using a particular fixation system. The SFEM corrected geometry was shown to compare favourably with the post-surgical curve. We have now developed an elastic beam-column model (EBCM) to which muscle activation forces, representing asymmetrical paralysis of the vertebral column muscles, can be applied to generate a given scoliotic curve. In that process the stiffness properties of the patient-simulated EBCM are determined. Now on these patient-simulated EBCM(s), identical corrective force systems are applied as developed by the finite-element model (SFEM) and implemented surgically for these patients. It is shown that the EBCM corrected geometries compare favourably with both SFEM corrected geometries as well as with the post-surgical curves for similar corrective force systems. Thus the EBCM can be employed to presurgically simulate scoliolic correction, specify the optimal corrective system of forces so as to gain the best surgical correction.