In the super-aged society, the social role of nursing care industries is increasing. Many workers in the industries have the low back pain. Countermeasures to prevent it in the field of nursing care are urgent issues. One of the causes of the low back pain is known as an increase in lumbar intervertebral pressure. However, it is very difficult to measure the lumbar intervertebral pressure in a non-invasive manner. The goal of this research is to develop a human body finite element (FE) model to estimate physical burden such as the low back pain. In this paper, we investigated the validity of model prediction such as muscle activity and intervertebral disc pressures in a half-crouching position, which is a common posture causing the low back pain. An experiment using a human adult male volunteer was conducted to compare with the prediction results. The participant kept a half-crouching position while holding a box with his both hands. Activity of 16 superficial muscles was measured in three conditions of 0.6 kg, 9.2 kg, and 18.0 kg as the weight of the box. Under three conditions similar to the experiment, the muscle activity and intervertebral disc pressures when holding a box in a half-crouching posture were calculated using the human body FE model. The trend of change in the calculated muscle activation levels for each box weight generally showed good agreement with the experimental data. Predicted results of intervertebral disc pressures from the third lumbar to the fifth lumbar spine vertebra generally agreed with test data obtained from the literature. Muscle activity and distributions of intradiscal pressures, muscle contractile forces, and tensile strains of muscle and tendon changed according to the weight of the box. These results demonstrated that this model has the possibility of evaluating physical burden when holding a box.
The objective of this study is to present a potential mechanism for traumatic brain injury resulting from a lateral blunt impact to the head during SUV-to-pedestrian impact. An AM50th percentile model of the human head was developed, and the mechanical response predicted by the model was validated against available cadaveric test data. It was found that the traction force due to the inertia of the brain mass plays a key role in brainstem lesion prior to the primary contact as well as the local stress/strain distribution around the lateral ventricle immediately after the contact with a vehicle. For the covering abstract see ITRD E141569.
Abstract We developed a 50th-percentile American male pedestrian model including a detailed brain, and the mechanical responses and kinematic biofidelity predicted by this model were validated against the available cadaveric test data. Vehicle-to-pedestrian impact simulations were then performed to investigate a potential mechanism for traumatic brain injury resulting from a lateral blunt impact to the head. Due to inertia of the brain mass, it was found that the average traction force produced in the cervical spinal cord exceeded 50 N in the impact involving a sport utility vehicle and 25 N in the impact involving a sedan, when the striking vehicle was travelling at 40 km/h. This inertial loading may play a key role in a brainstem, or upper-cervical-cord, lesion occurring before head strike. Results of this study suggest that close attention should be paid to pedestrian kinematics during free flight even before the head makes primary contact with the striking vehicle. Keywords: traumatic brain injuryvehicle-to-pedestrian impacttraction forcecervical spinal cordbrainstemdiffuse axonal injury Acknowledgment The authors thank the staff of Bioengineering Center, Wayne State University, for their contribution to the development of the head and thoracic parts of our human model, THUMS.
The occurrence of diseases characterized by irregular spinal alignment, such as kyphosis, lordosis, scoliosis, and dropped head syndrome (DHS) is increasing, particularly among older adults. DHS is characterized by an excessive forward tilt of the head and neck, causing the head to droop. Although it is believed that muscle activity plays a role in both the onset and treatment of DHS, the underlying mechanisms remain unclear. To elucidate the mechanism, we used a human body finite element model, which included the erector spinae muscle group, and a muscle controller with fixed legs for spinal posture stabilization. The model replicated muscle activation levels during the maintenance of an upright posture under gravity, similar to those obtained from experimental data. Parametric simulations to investigate the effect of each spinal muscle impairment on upright posture with and without compensatory activities of the other muscles suggest that trunk extensors; the multifidus L1-S and longissimus thoracis muscles, and hip flexors; psoas major and iliacus muscles play an integral role in maintaining an upright posture. These findings support the results of a rehabilitation study that reported that exercises targeting the trunk, psoas muscles, and cervical extensors could improve global spinal alignment and clinical outcomes in DHS.
Elucidating the mechanisms of mild traumatic brain injuries (mild TBIs), including concussions, is important for developing brain injury criteria and designing head protection devices. Using a finite element (FE) model of the human brain to predict the deformation of the brain parenchyma during a head impact could provide mechanical insights on mild TBIs. However, most conventional brain FE models do not consider how fluid behavior and the perfusion pressure of the cerebrospinal fluid (CSF) will affect brain deformation. This study proposes a novel brain FE model that uses incompressible fluid dynamics (ICFD) to represent the fluid behavior of CSF in the ventricle. In the model with ICFD, the validation accuracy scores on the brain strain during a head impact with a rotational acceleration were significantly higher than those in the model without ICFD. Reconstruction simulations based on two reported mild TBI cases from a rear-end collision and an American football game were conducted using the model with and without ICFD. We found that the maximum principal strain values in the subcortical region and corpus callosum of the model with ICFD were higher and lasted longer than those of the model without ICFD, and this tendency was further enhanced when perfusion pressure was applied. These findings suggested that the fluid behavior and perfusion pressure of the intraventricular CSF could significantly affect the deformation of the brain parenchyma during head impacts. The proposed brain multiphysical FE model could enhance the understanding of mild TBI mechanisms. Mild TBIs or concussions can result from brain deformations caused by the rapid acceleration of the head in the situations such as falls, vehicular accidents, and collisions in sports-related activities. A FE analysis is an effective tool for simulating head impact scenarios associated with mild TBIs and estimating the brain strain. Accurate prediction of mild TBIs requires a brain FE model with high biofidelity. Here, we firstly revealed that the validation accuracy of the model on the brain strain can be improved by considering the fluid behavior of intraventricular CSF. By analyzing existing mild TBI cases using the proposed model, the fluid behavior and perfusion pressure of the CSF were found to significantly affect the brain strain history, resulting in an outcome similar to the clinical symptom. The proposed multiphysical brain model could potentially provide new mechanical insights and further understanding of mild TBIs. Additionally, these findings in this study could be useful in developing brain injury criteria and designing protective equipment.
A tilt-rotating seat was developed to induce trunk movements by slowly and slightly changing the seat angle to make sedentary time a health-improving time. This approach was inspired by the unconscious postural control of humans. Comparing the effect of the tilt-rotating seat to a regular seat using a finite element model of the human body, it was found that the activity level of deep muscles changed over time. This result suggests that this chair may potentially reduce the physical burden during sedentary time and provide a different type of exercise with unique characteristics compared to traditional exercise.
Higher brain dysfunction due to traumatic brain injury (TBI) caused by head rotational impact in traffic accidents is one of the most serious automotive safety problems. However, the injury mechanism still remains unclear. In this study, we developed two human head finite element (FE) models based on THUMS for further understanding of TBI mechanism. Parametric studies were performed to investigate the factors affecting brain tissue displacements and intracranial pressures during head impact by using these models. The mesh fineness, material properties of cerebrospinal fluid (CSF) and contact conditions between brain parenchyma and surrounding external organisation had little influence on validation accuracy against test data on brain responses of post mortem human subjects (PMHS). However, there were significant differences in the values of cumulative strain damage measure (CSDM) and the contours of strain distribution between these models. These findings have the potential for better understanding of TBI mechanism.
