Sex, Age and Stature Affects Neck Biomechanical Responses in Frontal and Rear Impacts Assessed Using Finite Element Head and Neck Models

Abstract

The increased incidence of injury demonstrated in epidemiological data for the elderly population, and females compared to males, has not been fully understood in the context of the biomechanical response to impact. A contributing factor to these differences in injury risk could be the variation in geometry between young and aged persons and between males and females. In this study, a new methodology, coupling a CAD and a repositioning software, was developed to reposture an existing Finite element neck while retaining a high level of mesh quality. A 5th percentile female aged neck model (F0575YO) and a 50th percentile male aged neck model (M5075YO) were developed from existing young (F0526YO and M5026YO) neck models (Global Human Body Models Consortium v5.1). The aged neck models included an increased cervical lordosis and an increase in the facet joint angles, as reported in the literature. The young and the aged models were simulated in frontal (2, 8, and 15 g) and rear (3, 7, and 10 g) impacts. The responses were compared using head and relative facet joint kinematics, and nominal intervertebral disc shear strain. In general, the aged models predicted higher tissue deformations, although the head kinematics were similar for all models. In the frontal impact, only the M5075YO model predicted hard tissue failure, attributed to the combined effect of the more anteriorly located head with age, when compared to the M5026YO, and greater neck length relative to the female models. In the rear impacts, the F0575YO model predicted higher relative facet joint shear compared to the F0526YO, and higher relative facet joint rotation and nominal intervertebral disc strain compared to the M5075YO. When comparing the male models, the relative facet joint kinematics predicted by the M5026YO and M5075YO were similar. The contrast in response between the male and female models in the rear impacts was attributed to the higher lordosis and facet angle in females compared to males. Epidemiological data reported that females were more likely to sustain Whiplash Associated Disorders in rear impacts compared to males, and that injury risk increases with age, in agreement with the findings in the present study. This study demonstrated that, although the increased lordosis and facet angle did not affect the head kinematics, changes at the tissue level were considerable (e.g., 26% higher relative facet shear in the female neck compared to the male, for rear impact) and relatable to the epidemiology. Future work will investigate tissue damage and failure through the incorporation of aged material properties and muscle activation.

Effect of muscle pre‐tension and pre‐impact neck posture on the kinematic response of the cervical spine in simulated low‐speed rear impacts

“…The C2 to C7 vertebrae (Figure 4) were repostured without retaining stresses to reflect reported data that were an average of 7 male MRI scans collected in a study that used a seat similar to the one used during the rear impact sled tests with volunteers 29 . The repositioning of the model to the new postures was conducted using the aforementioned vertebral positions as targets and PIPER software (http://piper-project.org), 30 using a methodology previously described in the literature 31 . The mesh quality of the repostured model was maintained using a set of mesh enhancement tools 32 together with a methodology previously described 31 .…”

“…31 The mesh quality of the repostured model was maintained using a set of mesh enhancement tools 32 together with a methodology previously described. 31 After repositioning the C2-T1 vertebrae, the head was rotated so that the Frankfort plane was horizontal for the cadaveric data and 10 above the horizontal plane for the volunteer data following the experimental methodology of each impact experiment.…”

“…29 The repositioning of the model to the new postures was conducted using the aforementioned vertebral positions as targets and PIPER software (piper-project.org), 30 using a methodology previously described in the literature. 31 The mesh quality of the repostured model was maintained using a set of mesh enhancement tools 32 together with a methodology previously described. 31 After repositioning the C2-T1 vertebrae, the head was rotated so that the Frankfort plane was horizontal for the cadaveric data and 10 above the horizontal plane for the volunteer data following the experimental methodology of each impact experiment.…”

Possibilities of personalized finite element segmental analysis of the cervical spine for predicting the course of dorsopathy

“…В эпидемиологических исследованиях продемонстрирована повышенная частота травм шеи при фронтальном ударе и хлыстовой травме среди пожилых людей и женщин по сравнению с мужчинами, которая может быть обусловлена комплексной биомеханической реакцией на такое воздействие. Иссле дование конечно-элементных моделей (Finite element model) показало, что факторами, способствующими различиям в риске получения травм шеи, являются различия в геометрии шеи, увеличенный лордоз и положение головы, размеры углов фасеточных суставов [9]. Многочисленные исследования количественно подтверждают эффективность применения компьютерного моделирования и конечно-элементного анализа (КЭА) в предоперационном планировании (исследование систем «костьпротез»), анализе диапазона движений в позвоночнике, напряжений в фасеточных суставах, дисках, связках и спинном мозге [10].…”

Explaining and predicting the increased thorax injury in aged females: age and subject-specific thorax geometry coupled with improved bone constitutive models and age-specific material properties evaluated in side impact conditions

“…The geometry was obtained through magnetic resonance imaging (MRI) and computer tomography (CT) scans of a subject reflecting the characteristics of a 5 th percentile female in terms of mass, stature, and BMI. Notably, the F05-O model was developed with mesh quality requirements to ensure numerical accuracy ( 11 ). The F05-O has undergone validation in various body regions, including the thorax, with specific focus on chest compression and the incorporation of hard tissue failure using element erosion ( 12 , 13 ).…”