RUGBY AND CERVICAL SPINE INJURY

The purpose of this presentation is to present an overview about cervical spine injuries and rugby. We focus first on global epidemiology of such injuries and on the associated injury mechanisms. Then we present the different actions developed during the last decades in order to reduce the number of injuries. In a final part, a new approach based on Finite Element Modelling is proposed to identify links between injury risks and specific anatomy

MODEL OF CALF MUSCLE TEAR DURING A SIMULATED ECCENT RlC CONT RACTlON. A FEASABILITY STUDY

Tearing of muscle-tendon complex is one of the main causes of sport injuries. The aim of this study was to combine passive stretching and contraction to model the conditions of such injury, using the discrete element method. The mechanical behavior of the muscle-tendon complex was in agreement with data from the literature and data from in vittu experiments by tensile tests on calf muscle-tendon unit. The localization of the rupture and the pattern of rupture show a delamination of muscle's fibers close to the myotendinous junction during an active stretching of the muscle-tendon complex

MORPHOLOGICAL INEQUITIES? NUMERICAL SIMULATION OF CERVICAL SPINE INJURIES IN RUGBY

The purpose of this study was to identify cenrical spine morphologies at risk in rugby games. A parameterized osteaarticular finite element model of the cervical spine modeled 17 subjects under three different loadings, each being representative of rugby game phases: scrum (unconstrained axial compression), tackle (full-constraint axial compression) and collapsing scrum (hyperflexion). Stress and strain in the spine were recorded to determine appearances of injuries. The comparison of these injuries with the literature validated the model for injury prediction. A correlation analysis linked parameters of the morphology with the injury prediction and key parameters such as articular facet orientation arose. Precisely identifying all these parameters could help designing preventive clinical guidelines for rugby 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. Moreover, a multi-joint kinematical model was created for each subject, based on a new 3-D minimally invasive stereoradiographic X-ray images to assess subject-specific geometry and inertial parameters. The simulations allowed discriminating between the contributions of the passive (inertia-induced properties) and the active (neuromuscular response) components during falls. Our data show that there is limited time to adjust the way one fall from a standing position. We showed that the pre-impact period is truncated of 200 ms. During the initial part of a fall, the observed trajectory results from the interaction between the destabilizing external force and the body: inertial properties intrinsic to joints, ligaments and musculotendinous system have then a major contribution, as suggested for the regulation of static upright stance. This passive phase is later followed by an active phase, which consists of a corrective response to the postural perturbation. We believe that during a fall from standing height, it takes about 300 ms for postural responses to start correcting the body trajectory, while the impact is expected to occur around 700 ms. It has been argued that this time is sufficient to change the way one falls and that this makes it possible to apply safer ways of falling, for example by using martial arts fall techniques. Also, our results imply visual and vestibular information are not congruent with the beginning of the on-going fall. This consequence is to be noted as subjects prepare to the impact on the basis of sensory information, which would be uniquely mainly of proprioceptive origin at the fall onset. One limitation of the present analysis is that no EMG was included so far but these data are the subject of a future study

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements