ABSTRACT
Objective To simulate the process of lumbar burst fracture by finite element method, and investigate stress distributions on the cancellous bone of lumbar vertebrae under axial compressive loads. Methods The 3D finite element model of normal human thoracolumbar motion segments (T12-L2) was established. Stress at different levels (0.4, 0.6, 0.8, 1.0, 1.2 kN) was applied on the surface of T12 thoracic vertebra to simulate the different axial compressive loads at the occurrence of lumbar burst fracture. The ligature between concave vertexes of the inferior and superior endplates was divided into 7 portions, and the cancellous bone of the L1 vertebra was then divided into 7 layers with each layer separated into 6 statistic zones. The average stress on 18 statistic zones at 3 layers (Layer 1, 4, 7) of the cancellous bone was calculated, respectively. The average stress on 3 layers under the same loads was analyzed by one-way ANOVA, and stress distribution on the cancellous bone of lumbar vertebrae under different loads was also analyzed. ResultsUnder axial loads at 5 different levels, the average stress on Layer 1 and Layer 7 had obvious statistical significance compared with that on Layer 4(P0.05). The stress on the middle layer (Layer 4) was the minimum compared with that on Layer 1 and Layer 7. Conclusions Under axial compressive loads, the stress concentration occurred in the cancellous bone of lumbar vertebrae. The stress at adjacent vertebral endplates (inferior and superior endplates) was larger, while the stress on the middle layer was relatively smaller. The phenomenon that vertebral stress concentrating on inferior and superior endplates was consistent with the biomechanical mechanism of broken endplates caused by lumbar burst fracture, which indicates that the damage to lumbar structure may be related to the stress concentration on lumbar vertebrae.