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Background. Vertebral column decancellation (VCD) is a new spinal osteotomy technique to correct thoracolumbar kyphotic deformity (TLKD). Relevant biomechanical research is needed to evaluate the safety of the technique and the fixation system. We aimed to develop an accurate finite element (FE) model of the spine with TLKD following VCD and to provide a reliable model for further biomechanical analysis. Methods. A male TLKD patient who had been treated with VCD on L2 and instrumented from T10 to L4 was a volunteer for this study. The CT scanning images of the postoperative spine were used for model development. The FE model, simulating the spine from T1 to the sacrum, includes vertebrae, intervertebral discs, spinal ligaments, pedicle screws, and rods. The model consists of 509580 nodes and 445722 hexahedrons. The ranges of motion (ROM) under different loading conditions were calculated for validation. The stresses acting on rods, screws, and vertebrae were calculated. Results. The movement trend, peak stress, and ROM calculated by the current FE model are consistent with previous studies. The FE model in this study is able to simulate the mechanical response of the spine during different motions with different loading conditions. Under axial compression, the rod was the part bearing the peak stress. During flexion, the stress was concentrated on proximal pedicle screws. Under extension and lateral bending, an osteotomized L1 vertebra bore the greatest stress on the model. During tests, ligament disruption and unit deletion were not found, indicating an absence of fracture and fixation breakage. Discussion. A subject-specific FE model of the spine following VCD is developed and validated. It can provide a reliable and accurate digital platform for biomechanical analysis and surgical planning.

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Subsystem impactor tests are the main approaches for evaluation of safety performance of vehicle front design for pedestrian protection in legislative regulations. However, the main aspects of vehicle safety for pedestrians are shape and stiffness, and though it is clear that subsystem impact tests encourage lower vehicle front stiffness, it is unclear whether they promote improved vehicle front shapes for pedestrian protection. The purpose of this paper is therefore to investigate the effects of European pedestrian safety regulations on passenger car front shape and pedestrian injury risk using recent German In-Depth Accident Study (GIDAS) pedestrian collision data and numerical simulations. Firstly, a sample of 579 pedestrian collision cases involving 190 different car models between 2000-2015 extracted from the GIDAS was used to compare front-end shapes of passenger cars manufactured before and after the legislative pedestrian safety regulations were introduced in Europe. The focus was on changes in passenger car front shape and differences in pedestrian AIS2+ (Abbreviated Injury Scale at least level 2) leg, pelvis/femur and head injury risk observed in collisions. Multi-body simulations were also used to assess changes in vehicle aggressivity due to the observed changes in vehicle shape. The results show that newer passenger cars tend to have a flatter and wider bumper, higher bonnet leading edge, shorter and steeper bonnet and a shallower windscreen. Both the collision data and the numerical simulations indicate that newer passenger car front bumper designs are significantly safer for pedestrians' legs. However, the results also show that the higher bonnet leading edge in newer passenger cars is poor for pedestrian pelvis/femur protection, even though newer cars show an obviously lower AIS2+ injury risk to younger pedestrians in collisions. Newer cars have a lower AIS2+ head injury risk for pedestrians in collisions, but the numerical analysis indicate that this is not likely due to shape changes in passenger car fronts. Overall, the introduction of pedestrian safety regulations has resulted in reductions in pedestrian injury risk, but further benefits would accrue from tests which promote a lower bonnet leading edge. The influence of vehicle shape on pedestrian head injury risk remains unclear.

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