ABSTRACT
Objective To predict and assess biomechanical responses and injury mechanisms of the thorax and abdomen for small-sized females in vehicle collisions. Methods The accurate geometric model of the thorax and abdomen was constructed based on CT images of Chinese 5th percentile female volunteers. A thoracic-abdominal finite element model of Chinese 5th percentile female with detailed anatomical structure was developed by using the corresponding software. The model was validated by reconstructing three groups of cadaver experiments (namely, test of blunt anteroposterior impact on the thorax, test of bar anteroposterior impact on the abdomen, test of blunt lateral impact on the chest and abdomen). Results The force-deformation curves and injury biomechanical responses of the organs from the simulations were consistent with the cadaver experiment results, which validated effectiveness of the model. Conclusions The model can be used for studying injury mechanisms of the thorax and abdomen for small-sized female, as well as developing small-sized occupant restraint systems and analyzing the forensic cases, which lays foundation for developing the whole body finite element model of Chinese 5th percentile female.
ABSTRACT
Objective By studying biomechanical responses of the femur-prosthesis-tibia complex under normal standing condition after tumor-type hinged knee arthroplasty, to investigate the cause of femoral perforation in patients after knee arthroplasty, so as to provide a theoretical basis for optimal design and manufacturing of tumor-type hinged artificial knee prosthesis. Methods By coupling CT and 3D optical scanning, the finite element model of the subject-specific femur-prosthesis-tibia complex was established and was validated regarding its availability, so as to analyze stress distribution and stress shielding phenomenon of the complex in standing position. Results (1) Under the loading state of standing, the stress on the femur was significantly larger than that on the tibia, and presented an evident concentration phenomenon. The proximal 1/3 of femoral shaft presented a larger stress, with a stress shielding effect. (2) As the model was based on geometry and bone characteristics of the patient in clinic, the location of femur stress concentration was close to that of femur perforation in the patient, which indicated that femur injury behavior might occur when its own gravity was applied such as the patient condition. Conclusions After implantation of the tumor-type hinged artificial knee prosthesis, the prosthesis marrow needle goes deep into marrow cavities, which brings certain pressure to the marrow cavities even under normal standing condition. The produced stress shielding effect and the match of the prosthesis marrow needle to the marrow cavity are all likely to cause stress concentration on the femur, even make femur crack or perforation, and eventually affect the surgery quality. Thus, the prosthesis design should be carefully optimized before surgery in order to reduce or avoid such phenomenon that is related to the postoperative complication rate.
ABSTRACT
Objective To investigate the effect of hip protector on biomechanical response of the human pelvis-femur complex under lateral pelvic impacts during sideways falls using three dimensional (3D) finite element (FE) method. Methods Based on the model database of China Mechanical Virtual Human, a 3D FE model of the pelvis-femur-soft tissue complex including cortical bone, cancellous bone and soft tissue capsule and the pelvis-femur-soft tissue complex with a two layer hip protector were created, respectively. The rigid plane model was also constructed in the two models for ground simulation and constrained in all freedoms. The average hip lateral impact velocity of 2 m/s was applied to the two models, and the time for simulation analysis was set at 20 ms. The stress and strain distribution on the two models under lateral impacts could be obtained by the 3D FE calculation. The comparative analysis was performed to study the effect of the hip protector on biomechanical response of the pelvis-femur complex. Results The hip protector made the peak Von Mises stress appeared 4 ms more earlier in the pelvis-femur complex with a significant decrease in the stress and strain level. The average Von Mises stress peak was decreased by 67.88% and 69.34% in the cortical bone and in the cancellous bone, respectively, and the compressive principal strain peak was decreased by 63%. Conclusions Under lateral pelvic impacts, the two-layer hip protector could act as safeguard for pelvis-femur complex, thus effectively prevent the occurrence or reduce the risk of bone fracture.
ABSTRACT
ObjectiveTo develop a finite element computational model of the torso for the numerical simulation of mechanical responses of human torso to non-penetrating ballistic impact. MethodsBased on the CT data of a Chinese adult man, the finite element model of human torso was created by using the medical image processing software Mimics and the finite element pre-processing software HyperMesh. The pressure and acceleration response of the human torso outfitted with soft body armor to the ballistic impact from 9 mm ammunition at a velocity of 360 m/s was calculated numerically by the explicit finite element code LS-DYNA. ResultsThe finite element model of human torso including thoracic skeletal structure, organs, mediastinum and muscle/skin was established. The pressure response of heart, lung, liver and stomach, as well as the acceleration response of sternum were obtained by numerical calculation. It was found that the peak pressure and its time phase were dependent on the distance between the impact point and the measured point wherever in various organs or different position of an organ. Conclusions The finite element computational model of human torso outfitted with soft body armor is available for the simulation of human response to non-penetrating ballistic impact, and the simulated response can be used as evidence for the investigation on mechanism and protection of behind armor blunt frauma.
ABSTRACT
The various biomechanical responses such as stress distribution, facet contact force and nucleus pressure change in the lumbar spine under vertical static and dynamic loading conditions were. Investigated with a nonlinear three dimensional finite element model. Finite element model of one motion segment, consisted of two vertebral bodies(L3-4) with one disc, was developed from 1 mm thick transverse CT cross-sections. Geometrical nonlinearity was also considered for the large deformation on the disc. ABACUS package was used for calculation and its results were verified comparing with the existing in-vitro experimental data. Clinically useful results could be obtained with this analysis. Stress was concentrated on the endplate under static and dynamic loading condition, especially posterior and anterior aspect and central portion along midsagittal plane. The facet contact force showed some discontinuity when Δt/2=0.03 sec. This discontinuity was considered to de due to the vibration of upper vertebra. Relatively smooth contact force profile was detected when t/2=0.1342 sec. Intradiscal pressure and stress pattern changes on the vertebra were also analyzed.