The cause of axial rotation of the scoliotic spine.
To explain the cause of axial rotation in a scoliotic vertebral column, the influence of the gravitation force on a spine with a C-scoliosis has been investigated by means of a mechanical model. In this model the gravitation force takes hold of the three-dimensionally curved vertebral column eccentrically. From these reflections it appears that the axial rotation in the scoliotic spine can be explained by the moment distribution caused by this eccentrical gravitation force. The moment distribution, necessary for correction of the spine, is supposed to be opposite to the moments caused by the gravitation force. The moment distribution caused by the Harrington and the Luque spinal correction systems are compared to the calculated optimum correction moments. It appears that the moment distribution for the Harrington and Luque methods, necessary for the correction of the lateral deviation, are almost the same as the calculated correction moments. But the axial rotation appears to be increasing instead of decreasing in both correction systems.
Assessment of ground reaction force during scoliotic gait
Although the causes and progression of adolescent idiopathic scoliosis (AIS) are still unclear, a recent extensive review has indicated a number of possible aetiological factors. Previous investigations, employing gait measurements, have indicated asymmetries in the ground reaction forces and suggest a relationship between these asymmetries, neurological dysfunction and spinal deformity. Using a strain-gauge force platform, the present study has examined the time-domain parameters of various components of the ground reaction force together with impulse. Symmetry indices (SI) between left and right sides have also been estimated. The results show that the patients with a left compensatory curve had a greater SI for a left-side impulse, whilst subjects with little or no compensation had a greater rightside impulse. This indicates that a possible gait compensation is occurring, so that the subjects compensate on the opposite pelvis/lower limb to that of the curve. While indicating the asymmetries between left and right, the results also serve to highlight the value of using kinetic parameters in developing the understanding of the pathogenesis and aetiology of scoliosis.
Analog studies of forces in the human spine: computational techniques.
Abstract A mathematical model is developed for a three-dimensional force analysis of the human vertebral column. The vertebrae are idealized as rigid bodies, while the discs, ligaments, and connective tissues are represented by deformable elements. An incremental stiffness method which accounts for nonlinearities due to large displacements is used. Preliminary results are presented for the behavior of an isolated, ligamentous column under traction, lateral loads, and compressive loads which result in buckling.