[Thoracolumbar burst fractures; an experimental study on cadaveric spines and finite element method].

A biomechanical study on cadaveric human and calf spines and finite element method (FEM) was carried out in order to detect the mechanism of thoracolumbar burst fractures and to investigate the influence of disc degeneration and bone mineral density (BMD). Eleven motion-segments of thoracolumbar spines from human cadavers and 5 ones from calf thoracolumbar spines were compressed vertically until a fracture occurred. Typical burst fracture occurred in seven of eleven human specimens and in all calves spines, which showed destruction of the middle end-plate and disc materials in the vertebral body. The fracture line was located between the middle of the end-plate and the middle of the posterior wall cortex. No burst fractures could be seen in the specimens with severely degenerated disc and osteoporosis. Finite element analysis corresponded to the results of experimental study. Therefore, the axial compression proved to induce typical burst fractures in the thoracolumbar spines. Mechanism of this fracture was influenced by bone mineral density and disc degeneration.