Geometric growth of the normal human craniocervical junction from 0 to 18 years old.

The craniocervical junction (CCJ) forms the bridge between the skull and the spine, a highly mobile group of joints that allows the mobility of the head in every direction. The CCJ plays a major role in protecting the inferior brainstem (bulb) and spinal cord, therefore also requiring some stability. Children are subjected to multiple constitutive or acquired diseases involving the CCJ: primary bone diseases such as in FGFR-related craniosynostoses or acquired conditions such as congenital torticollis, cervical spine luxation, and neurological disorders.

New diagnostic criteria for metopic ridges and trigonocephaly: a 3D geometric approach.

Background: Trigonocephaly occurs due to the premature fusion of the metopic suture, leading to a triangular forehead and hypotelorism. This condition often requires surgical correction for morphological and functional indications. Metopic ridges also originate from premature metopic closure but are only associated with mid-frontal bulging; their surgical correction is rarely required.

Personalised gravitational loading of the cervical spine from biplanar X-rays for asymptomatic and clinical subjects in neutral standing position.

Background: As a leading cause of disability with a high societal and economic cost, it is crucial to better understand risk factors of neck pain and surgical complications. Getting subject-specific external loading is essential for quantifying muscle forces and joint loads but it requires exertion trials and load cells which are uncommon in clinical settings.

Methods: This paper presents a method to compute the gravitational loading at four levels of the cervical spine (C3C4, C4C5, C5C6, C6C7) in neutral standing position from biplanar radiographs exclusively.

Paediatric skull growth models: A systematic review of applications to normal skulls and craniosynostoses.

Introduction: Craniosynostoses affect 1/2000 births and their incidence is currently increasing. Without surgery, craniosynostosis can lead to neurological issues due to restrained brain growth and social stigma due to abnormal head shapes. Understanding growth patterns is essential to develop surgical planning approaches and predict short- and long-term post-operative results.

Insights into the mechanical interaction between an active cranial implant and the skull subjected to moderate impact loadings.

In the context of cochlear implants, which are now widely used, and innovative active devices, the cranial implantation of electronic devices raises new questions about the mechanical interactions between the implant and the skull. The aim of this study was to build a methodology using experimental data and numerical simulations to evaluate the mechanical interactions between the skull and the WIMAGINE® active cranial implant intended for use for tetraplegic patients. A finite element model of the implant housing and a simplified model of the three-layered skull were developed.

Johnson-Cook Parameter Identification for Commercially Pure Titanium at Room Temperature under Quasi-Static Strain Rates.

Background: To simulate mechanical shocks on an intracranial implant called WIMAGINE, Clinatec chose a Johnson-Cook model to account for the viscoplastic behavior of grade 2 titanium in a dynamic study using Radioss.

Methods: Thirty tensile specimens were subjected to tensile tests at room temperature, and the influence of the strain rate (8 × 10 and 8 × 10 s) and sandblasting was analyzed. Relaxations were included in the tests to analyze viscosity phenomena.

Modeling of muscular activation of the muscle-tendon complex using discrete element method.

The tearing of a muscle-tendon complex (MTC) is caused by an eccentric contraction; however, the structures involved and the mechanisms of rupture are not clearly identified. The passive mechanical behavior the MTC has already been modeled and validated with the discrete element method. The muscular activation is the next needed step.

Surface reconstruction from routine CT-scan shows large anatomical variations of falx cerebri and tentorium cerebelli.

Background: Finite element modeling of the human head offers an alternative to experimental methods in understanding the biomechanical response of the head in trauma brain injuries. Falx, tentorium, and their notches are important structures surrounding the brain, and data about their anatomical variations are sparse.

Objective: To describe and quantify anatomical variations of falx cerebri, tentorium cerebelli, and their notches.

Corrigendum: An Initial Passive Phase That Limits the Time to Recover and Emphasizes the Role of Proprioceptive Information.

[This corrects the article DOI: 10.3389/fneur.2018.

Collaborative sensorimotor intelligence: the scrum as a model.

Aim: Using M-Rex, a rugby scrum simulator, we developed tools to describe scrummaging forces and to prevent accident.

Methods: We tested three groups of frontliners at national level. The simulator was passive or responded to the player(s) to simulate the reaction of opposite players.

An Initial Passive Phase That Limits the Time to Recover and Emphasizes the Role of Proprioceptive Information.

In the present experiments, multiple balance perturbations were provided by unpredictable support-surface translations in various directions and velocities. The aim of this study was to distinguish the passive and the active phases during the pre-impact period of a fall. It was hypothesized that it should be feasible if one uses a specific quantitative kinematic analysis to evaluate the dispersion of the body segments trajectories across trials.

Inconsistent anticipatory postural adjustments (APAs) in rugby players: a source of injuries?

Background: We are developing since 2010 with Thales and the (FFR) M-Rex, a new kind of rugby scrum simulator. The study questioned whether it could improve safety and protect players from injury by using it as a tool for training/coaching the packs.

Aim: To explore the anticipatory postural adjustments (APAs) during the engagement of the ruck, because these predictive neck and back muscles contractions protect the spinal cord at the time of impacts, which is crucial to prevent injuries.

A subject-specific biomechanical control model for the prediction of cervical spine muscle forces.

Background: The aim of the present study is to propose a subject-specific biomechanical control model for the estimation of active cervical spine muscle forces.

Methods: The proprioception-based regulation model developed by Pomero et al. (2004) for the lumbar spine was adapted to the cervical spine.

An Attempt of Early Detection of Poor Outcome after Whiplash.

The main concern with whiplash is that a large proportion of whiplash patients experience disabling symptoms or whiplash-associated disorders (WAD) for months if not years following the accident. Therefore, identifying early prognostic factors of WAD development is important as WAD have widespread clinical and economic consequences. In order to tackle that question, our study was specifically aimed at combining several methods of investigation in the same WAD patients at the acute stage and 6 months later.

Non-invasive assessment of human multifidus muscle stiffness using ultrasound shear wave elastography: A feasibility study.

There is a lack of numeric data for the mechanical characterization of spine muscles, especially in vivo data. The multifidus muscle is a major muscle for the stabilization of the spine and may be involved in the pathogenesis of chronic low back pain (LBP). Supersonic shear wave elastography (SWE) has not yet been used on back muscles.

Kinetic DTI of the cervical spine: diffusivity changes in healthy subjects.

Introduction: The study aims to assess the influence of neck extension on water diffusivity within the cervical spinal cord.

Methods: IRB approved the study in 22 healthy volunteers. All subjects underwent anatomical MR and diffusion tensor imaging (DTI) at 1.

Study on cervical muscle volume by means of three-dimensional reconstruction.

Purpose: To quantify the cervical muscle volume variation by means of three-dimensional reconstruction from MRI images.

Materials And Methods: Sixteen subjects were scanned using a Philips MRI scanner, including 11 men and 5 women, aged from 23 to 33 years, weighting between 49-80 kg. The deformation of a parametric specific object method was used to develop three-dimensional muscle models from contours on a small number of MRI images.

Hyper-elastic properties of the human sternocleidomastoideus muscle in tension.

Numerical models of the human body require realistic mechanical properties of the muscles as input, but, generally, such data are available only for animals' muscles. As a consequence, the aim of this study was to identify the hyper-elastic behavior of the human sternocleidomastoideus muscle in tension using different constitutive laws. Ten sternocleidomastoideus muscles were tested in vitro.

The non-linear response of a muscle in transverse compression: assessment of geometry influence using a finite element model.

Most recent finite element models that represent muscles are generic or subject-specific models that use complex, constitutive laws. Identification of the parameters of such complex, constitutive laws could be an important limit for subject-specific approaches. The aim of this study was to assess the possibility of modelling muscle behaviour in compression with a parametric model and a simple, constitutive law.

Three-dimensional assessment of the intervertebral kinematics after Mobi-C total disc replacement at the cervical spine in vivo using the EOS stereoradiography system.

Background: Because 3-dimensional computed tomography and magnetic resonance imaging analysis of the spinal architecture is done with the patient in the supine position, stereoradiography may be more clinically relevant for the measurement of the relative displacements of the cervical vertebrae in vivo in the upright position. The innovative EOS stereoradiography system was used for measuring the relative angular displacements of the cervical vertebrae in a limited population to determine its feasibility. The precision and accuracy of the method were investigated.