A review of pelvic fractures in adult pedestrians: experimental studies involving PMHS used to determine injury criteria for pedestrian dummies and component test procedures

Development of a biofidelic computational model of human pelvis for predicting biomechanical responses and pelvic fractures

BACKGROUND AND OBJECTIVE

The pelvis, a crucial structure for human locomotion, is susceptible to injuries resulting in significant morbidity and disability. This study aims to introduce and validate a biofidelic computational pelvis model, enhancing our understanding of pelvis injury mechanisms under lateral loading conditions.

METHODS

The Finite Element (FE) pelvic model, representing a mid-sized male, was developed with variable cortical thickness in pelvis bones. Material properties were determined through a synthesis of existing constitutive models, parametric studies, and multiple validations. Comprehensive validation included various tests, such as load-displacement assessments of sacroiliac joints, quasi-static and dynamic lateral compression on the acetabulum, dynamic side impacts on the acetabulum and iliac wing using defleshed pelvis, and lateral impacts by a rigid plate on the full body's pelvis region.

RESULTS

Simulation results demonstrated a reasonable correlation between the pelvis model's overall response and cadaveric testing data. Predicted fracture patterns of the isolated pelvis exhibited fair agreement with experimental results.

CONCLUSIONS

This study introduces a credible computational model, providing valuable biomechanical insights into the pelvis' response under diverse lateral loading conditions and fracture patterns. The work establishes a robust framework for developing and enhancing the biofidelity of pelvis FE models through a multi-level validation approach, stimulating further research in modeling, validation, and experimental studies related to pelvic injuries. The findings are expected to offer critical perspectives for predicting, preventing, and mitigating pelvic injuries from vehicular accidents, contributing to advancements in clinical research on medical treatments for pelvic fractures.

A probabilistic model for murder weapon identification using stab-marks in human ribs

The aim of this article is to provide a scientific and statistical basis to identify the murder weapon in stabbing cases from the geometric characteristics of the stab-marks left on human ribs. For this purpose, a quantitative predictive model is developed, based on geometric measurements of the stab-mark and its location along the rib. A general method based on Bayesian inference and probabilities is used for the model development, rather than a deterministic model given its inability in certain occasions to identify the murder weapon. Following the process explained in this article to collect the stab-mark information required, the complete probabilistic model exposed attained a high accuracy in the identification of the murder weapon between two macroscopically identical blades with a microscopic alteration in one of them (more than 90% of correct identification is achieved).

Dynamic Simulation of Biomechanical Behaviour of the Pelvis in the Lateral Impact Loads

The objective of this study was to develop and validate a novel 3D dynamic model of a pelvic side-impactor system. The biomechanical responses of a pelvic flexible model (having .mnf file suffix) under the lateral impact load for predicting the bone fracture mechanism are investigated as well. The 3D solid model of the side-impactor system was imported into MSC/ADAMS software for analyzing the dynamic model, and the pelvic flexible model was extracted from the CT images of a Chinese female volunteer. The flexible model of the pelvis system was developed considering a wide range of mechanical properties in the bone complex and soft tissue to achieve a realistic biomechanical response during a lateral impact. Good agreements were achieved between the dynamic simulations and the experimental results of pelvic side impacts, in terms of the biomechanical criteria. The dynamic model of impactor system could be employed to investigate the hip protector effectiveness, improving the vehicle safety, and biomechanical response of the other human organs.

True compression of pelvic fractures under lateral impact

PURPOSE

To promote the understanding of pelvic fracture mechanism and make more accurate evaluation of maximal deformity at the moment of fracture, kinematic response of pelvis to lateral impact and the difference between peak and final displacement were investigated.

METHODS

A total of three human cadaver pelves were seated uprightly on a sled test table, explored to horizontal lateral impact by a 22.1-kg impactor at a speed of 5.2, 4.0, and 4.8 m/s. Kinematic data of pelvic osseous interesting points (POIP) were measured by the motion capture system. Trajectories of POIP, duration of impact, and deflection of pelvis were calculated as well as rotational movement of pelvis was evaluated. After impact, autopsy and CT scan were made to validate the motion capture data.

RESULTS

The peak deflection of pelvis under lateral impact was 31.9, 30.1, and 18.5%, while final deflection was 19.6, 13.8, and 13.8%. The final deflection was only 61.5, 45.9, and 74.46% of the peak deflection.

CONCLUSIONS

In clinical practice, pelvic fracture displacement tends to be underestimated. The peak compression can be 1.3-2.2 times of final compression appearing on images in hospital. Clinicians shall give adequate estimation of displacement and related injuries.