The effect of soft tissue stiffness on spinal flexibility: a finite element study of scoliosis

Pre-operative coronal curve flexibility assessment is of key importance in the surgical planning process for scoliosis correction. The fulcrum bending radiograph is one flexibility assessment technique which has been shown to be highly predictive of potential curve correction using posterior surgery, however little is known about the extent to which soft tissue structures govern spinal flexibility. The aim of this study was to explore how the mechanical properties of spinal ligaments and intervertebral discs affect coronal curve flexibility in the fulcrum bending test. To this end a biomechanical analysis of a scoliotic thoracolumbar spine and ribcage was carried out using a three dimensional finite element model. Study results concluded that disc collagen fibre and ligament stiffness both have minimal influence on scoliotic curve flexibility. However, discectomy simulation shows that the intervertebral discs are of critical importance in determining spinal flexibility