Analysis of isometric cervical strength with a nonlinear musculoskeletal model with 48 degrees of freedom

Abstract

Background:Musculoskeletal models served to analyze head-neck motion and injury during automotive impact. Although muscle activation is known to affect the kinematic response, a model with properly validated muscle contributions does not exist to date. The goal of this study was to enhance a musculoskeletal neck model and to validate passive properties, muscle moment arms, maximum isometric strength, and muscle activity.Methods: A dynamic nonlinear musculoskeletal model of the cervical spine with 48 degrees of freedom was extended with 129 bilateral muscle segments. The stiffness of the passive ligamentous spine was validated in flexion/extension, lateral bending, and axial rotation. Instantaneous joint centers of rotation were validated in flexion/extension, and muscle moment arms were validated in flexion/extension and lateral bending. A linearized static model was derived to predict isometric strength and muscle activation in horizontal head force and axial rotation tasks.Results: The ligamentous spine stiffness, instantaneous joint centers of rotation, muscle moment arms, cervical isometric strength, and muscle activation patterns were in general agreement with biomechanical data. Taking into account equilibrium of all neck joints, isometric strength was strongly reduced in flexion (46 %) and axial rotation (81 %) compared to a simplified solution only considering equilibrium around T1-C7, while effects were marginal in extension (3 %).Conclusions: For the first time, isometric strength and muscle activation patterns were accurately predicted using a neck model with full joint motion freedom. This study demonstrates that model strength will be overestimated particularly in flexion and axial rotation if only muscular moment generation at T1-C7 is taken into account and equilibrium in other neck joints is disregarded.

A Novel Approach to Measuring Muscle Mechanics in Vehicle Collision Conditions

“…The spine ligaments exhibit characteristic behaviour with small stiffness in the “toe” region and a nearly linear response in the elastic region [50], which results in low bending stiffness in the physiological range of motion of cervical segments, including skull-C2 [16,51,52]. Therefore, the bending moment is mostly counteracted by the neck extensor muscles, even more so in the low-severity frontal impacts performed in our study.…”

“…Several assumptions and input parameters that are difficult to determine accurately are needed for the muscle model, such as muscle physiology, interaction with the surrounding anatomical structures during motion, muscle activation, and load distribution over redundant muscles. Based on the measured body segment kinematics and external loads data, inverse dynamic analysis can retrieve the joint moment generated by a group of muscles; the individual muscle forces can then be estimated with the help of optimisation methods to resolve the force distribution between the redundant muscles acting on the joint [15,16,17,18,19,20]. In forward dynamic analysis of the musculoskeletal model, muscle activations can be optimised to produce muscle forces that minimize the difference between the simulated and the measured human body motion.…”

Neck postural stabilization, motion comfort, and impact simulation

“…Gravity is simulated as a 9.81 m/s 2 gravitational field acting on the skull and the vertebrae. The neck model was validated in passive bending and twist and in isometric loading where the ligamentous spine stiffness, instantaneous joint centers of rotation, muscle moment arms, cervical isometric strength, and muscle activation patterns were in general agreement with biomechanical data (de Bruijn et al, 2015). The control model, parameter estimation, and validation in anterioreposterior loading can be found in the article by Happee et al (2017).…”

“…Happee et al (2017) presented a multisegment cervical spine model with postural stabilization through VCR and CCR loops and cocontraction. A 3D multisegment nonlinear neck model(de Bruijn, van der Helm, & Happee, 2015; …”

The inclusion of hyoid muscles improve moment generating capacity and dynamic simulations in musculoskeletal models of the head and neck

“…Models of the head and neck are often used to investigate the injury potential of automobile impacts [ 3 – 5 ]. De Bruijn et al [ 6 ] recently published a detailed finite element model with 48 degrees of freedom and validated the muscle response to investigate head and neck motion during automotive impacts. A model designed for similar applications among female subjects was recently created by Östh et al [ 7 ].…”