Development of a multi-body computational model of human head and neck

Abstract

Citation: VAN LOPIK, D.W. and ACAR, M., 2007. Development of a multibody computational model of human head and neck. Proceedings of the IMechE, Part K: Journal of Multi-body Dynamics, 221 (2), pp. Additional Information:• This is an article from the journal, Proceedings of the IMechE, Abstract: Experimental studies using human volunteers are limited to low acceleration impacts while whole cadavers, isolated cervical spine specimens, and impact dummies do not normally reflect the true human response. Computational modelling offers a cost effective and useful alternative to experimental methods to study the behaviour of the human head and neck and their response to impacts to gain insight into injury mechanisms.This article reports the approach used in the development of a detailed multi-body computational model that reproduces the head and cervical spine of an adult in the upright posture representing the natural lordosis of the neck with mid-sagittal symmetry. The model comprises simplified but accurate representations of the nine rigid bodies representing the head, seven cervical vertebrae of the neck, and the first thoracic vertebra, as well as the soft tissues, i.e. muscles, ligaments, and intervertebral discs. The rigid bodies are interconnected by non-linear viscoelastic intervertebral discs elements in flexion and extension, non-linear viscoelastic ligaments and supported through frictionless facet joints. Eighteen muscle groups and 69 individual muscle segments of the head and neck on each side of the body are also included in the model. Curving the muscle around the vertebrae and soft tissues of the neck during the motion of the neck is also modelled. Simulation is handled by the multi-body dynamic software MSC.visuaNastran4D. Muscle mechanics is handled by an external application, Virtual Muscle, in conjunction with MSC.visuaNastran4D that provides realistic muscle properties. Intervertebral discs are modelled as non-linear viscoelastic material in flexion and extension but represented by 'bushing elements' in Visual Nastran 4D, which allows stiffness and damping properties to be assigned to a joint with required number of degrees of freedom of the motion. Ligaments are modelled as non-linear viscoelastic spring-damper elements.As the model is constructed, the cervical spine motion segments are validated by comparing the segment response to published experimental data on the load-displacement behaviour for both small and large static loads. The response of the entire ligamentous cervical spine model to quasi-static flexion and extension loading is also compared to experimental data to validate the model before the effect of muscle stiffening is included. Moreover the moment-generating capacity of the neck muscle elements has been compared against in vivo experimental data.The main and coupled motions of the model segments are shown to be accurate and realistic, and the whole model is in good agreement with experimental findings from actual human cervical spine specimens. It has been shown that the mode...

Application of the MEBDFV solver to dynamic simulation of some specific multibody systems: an example of a cervical spine model

“…As can be seen, the equations of motion (43) can be rearranged and presented in the matrix form (1), where (47) and the matrix M consists of the coefficients a i j .…”

“…6, shape representation of every body is based on eight characteristic points. Similar to the models described in [46,47], the center of mass is positioned at the center of the segment connecting the corners P 1 and P 6 of the vertebral body. It is assumed that point P 5 of the ith member and P 2 of the next one are coupled by a link rigidly connected with the lower body, and the pivot O i+1 is located in the point P 2 .…”

“…However, geometric representation of the skull is used mainly for visual purposes. Inertial properties of the vertebrae and head are adapted from [32,47]. Values of the elastic-dissipative parameters have been selected by trial and error.…”

Linear Homeomorphic Models for Muscles in the Head–Neck Region

“…The maximum isometric force was computed for each muscle as the product of the physiological crosssectional area of the muscle times the specific tension of the muscle, considered to be 31.8 N/cm 2 as in earlier reports. 3,28 The cost function used to find the best match between the two models was selected to include the force-velocity relationship comparison and the lengthtension profile generated in these isotonic experiments. Using this ad hoc cost function, the optimization problem is stated as…”

On the modeling of the intervertebral joint in multibody models for the spine

“…The approximate similarity between the bushing element and the intervertebral joint has led to its increased use in musculoskeletal models of the spine (see [7,14,16,19,20,21,23]). Here, we describe in further detail the application of the bushing element to model the intervertebral joint and clarify some common misconceptions.…”