Research On The Mechanism Of Traffic Secondary Injury And The Quantitative Analysis Of Death Risk Based On Numerical Simulation

Objective:By taking advantage of the combination of medical and industrial disciplines,a method of on-site evidence collection and numerical simulation reconstruction of traffic accident secondary injury cases with multi-information fusion was established,and the multi-rigid-body coupled finite element method was applied to solve the injury mechanism of traffic accident secondary injury,and the risk prediction equation of traffic accident death was constructed to transform the morphological discrimination problem into a biomechanical numerical quantification problem.The objective of this study is to provide new ideas and methods for the case identification and responsibility identification of traffic accident secondary injury.Methods:（1）A retrospective study and statistical analysis of 63 cases involving secondary injuries in traffic accidents from 2015 to 2022 were conducted to summarize the injury characteristics and injury mechanism of secondary injuries in traffic accidents.（2）New evidence collection technologies such as UAV tilt photography,optical scanning and video data were used to construct a digital model of traffic accident site-vehicle-person.On the basis of ensuring the comprehensively of accident data collection,multi-rigid body and finite element method simulation coupled genetic algorithm were used to construct an optimized digital simulation solution model and systematically solve the injury mechanism.To establish a biomechanical method for the identification of injury mode under the condition of injury superposition..（3）The widely accepted injury criterion,such as the linear head acceleration（Lin.acc）,the head rotational angular velocity（Ang.acc）,the generalized acceleration model（GAMBIT）,the maximum impact energy（HIP）,the head injury criterion（HIC）,the maximum Shear stress,VM stress,intracranial positive pressure（Cp）,intracranial negative pressure（CCp）,maximum principal strain（MPS）,cumulative strain damage criteria(CSDM_0.15and CSDM_0.25),Dilatation Damage Measure（DDM）,thorax 3ms and viscous criteria（VC）was evaluated based on 45 typical pedestrian accident cases.The correlation between injury criteria and death consequences was also evaluated.The dominant injury criteria were selected as predictive factors to construct multiple logistic regression prediction equation of death risk,and the death risk prediction equation was applied based on 6 real secondary injury cases of traffic accidents.The results were compared and evaluated with the traditional identification results and injury results.Results:（1）Retrospective analysis showed that the secondary injuries in traffic accidents were more common in males than females,and were more common in the age group of 50-70 years old.There were significant differences in the modes of injury between Traffic secondary accident.At the first time,the injuries were mainly caused by impact injury,followed by falling injury,and in the second time,the injuries were mainly caused by rolling injury,followed by crushing injury.There are also significant differences between the injury types and injury sites,among which the first injury type is mainly impact injury,injury site is mainly head injury,the second injury is mainly crushing injury,mainly chest injury.（2）Using UAV aerial photography,optical scanning,photogrammetry,CT/MRI and other technologies,combined with digital simulation methods such as multi-rigid body and finite element method,successfully established a traffic accident scene evidence collection system based on multi-information fusion and a digital simulation reconstruction method of traffic accidents and applied it to real identification cases.Objective mechanical data were used to explain the dose-effect relationship between injury consequence and injury mode.In one case,the simulation results were in good agreement with the actual situation in terms of kinematic behavior and collision position,which effectively evaluated the degree of injury caused by a vehicle-pedestrian collision.In the other case,the technical demonstration was realized to determine the injury mode of fatal skull ring fracture of a motorcycle driver in secondary injuries of traffic accidents.At the same time,the optimization model of genetic algorithm based on Euclidean distance between matching collision point pairs is realized,which avoids the influence of human factors effectively.（3）The results of the multi-rigidbody coupled finite element simulation reconstruction of 45 typical pedestrian traffic accidents are consistent with the accident data.GAMBIT,HIP,DDM,CSDM0.15,Cp,Thorax 3ms and VC are strongly correlated with the death consequences,which can be used as the predictor of the death risk equation.The AUC value of ROC curve of the death risk equation reached 0.9671,and the overall prediction accuracy reached 91.1%.In the 6 cases of secondary injury in traffic accidents,the prediction results of death risk in 4 cases were consistent with the traditional identification opinions,and the other 2 cases were not fully consistent with the forensic results,mainly related to the uncertain responsibility of the accident.Conclusions:The numerical simulation reconstruction method based on multi-information fusion of traffic accident scene evidence collection and genetic algorithm optimization,the evaluation of screened injury criteria and the death risk prediction equation established by this research can reasonably explain the location,cause and degree of damage and predict the death risk of traffic accidents.It provides a new idea,a new theory and a scientific technical support for the quantitative analysis of the death causes and death risks of secondary injuries in the practice of forensic medicine.