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A method to evaluate the effectiveness of wearable airbag protectors for motorcyclists is proposed in this work. The mitigation of thoracic injury severity in relevant accident conditions was investigated by a multimodel numerical approach. A set of impact conditions, obtained from previous work using multibody models, was used as input data to support the detailed analysis of injury risk with finite element models. The HUMOS II human model and an airbag model were validated from experimental data and coupled to evaluate the performance of the protector. Multiple frontal thoracic impact conditions were simulated on the human model by testing the airbag protector and reference simulations without any protection. A reduction on the skeletal AIS score of 1 was obtained, while the probability of sustaining severe soft tissue injuries was reduced by up to 22% with the safety device. Impact velocity and impactor shape were identified as relevant injury risk factors. [ABSTRACT FROM AUTHOR]

Posterior ligamentous complex (PLC) and intervertebral disc (IVD) injuries are common cervical spine flexion-distraction injuries, but the residual stability following their disruption is misknown. The objective of this study was to evaluate the effect of PLC and IVD disruption on post-traumatic cervical spine stability under low flexion moment (2 Nm) using a finite element (FE) model of C2-T1. The PLC was removed first and a progressive disc rupture (one third, two thirds and complete rupture) was modeled to simulate IVD disruption at C2-C3, C4-C5 and C6-C7. At each step, a non-traumatic flexion moment was applied and the change in stability was evaluated. PLC removal had little impact at C2-C3 but increased local range of motion (ROM) at the injured level by 77.2% and 190.7% at C4-C5 and C6-C7, respectively. Complete IVD rupture had the largest impact on C2-C3, increasing C2-C3 ROM by 181% and creating a large antero-posterior displacement of the C2-C3 segment. The FE analysis showed PLC and disc injuries create spinal instability. However, the PLC played a bigger role in the stability of the middle and lower cervical spine while the IVD was more important at the upper cervical spine. Stabilization appears important when managing patients with soft tissue injuries. [ABSTRACT FROM AUTHOR]

Cage subsidence in transforaminal lumbar interbody fusion (TLIF) is one of the concerns. The objective was to numerically assess the resulting segmental lumbar lordosis (SLL) and stresses at the bone-cage interface as functions of cage height (8- vs. 10-mm) and cage placement (oblique asymmetric, vs. anterior symmetric) for normal and osteoporotic bone quality. A L4-L5 detailed finite element model of TLIF was subjected to the functional loadings of 10 Nm in the physiological planes after the application of a 400 N follower-load. The SLL was increased by 0.9° (11%) and 1.0° (13%), respectively in oblique asymmetric and anterior symmetric cage placement with 8-mm height; they were 1.4° (18%) and 1.7° (21%) for the 10-mm cage. The maximum stresses at the cage-bone interface, in normal bone model, were increased up to 16% and 41% with the 10-mm cage and asymmetric oblique placement, respectively, and they increased up to 16% and 43% in osteoporotic bone model. The greater cage resulted to a higher simulated SLL. Oblique asymmetric placement and the use of a greater cage may increase the risk of cage subsidence. Due to the lower mechanical strength of osteoporotic bone, the risk of cage subsidence should be higher. [ABSTRACT FROM AUTHOR]

This work aimed to describe the helmeted head mobility as a combination of rotations and translations during functional head movements. A motion capture system was used to follow six optoelectronic markers placed on a motorcycle helmet worn by volunteers performing head motions (flexion-extension (FE), axial rotation (AR) and lateral bending (LB)). Maximum angular rotations and linear displacements were computed to assess intra-class correlation coefficients, standard errors of measurement and minimal detectable changes. Rotational range of motion was 101.9° (SD 17.8°) for FE, 78.8° (SD 13.8°) for LB and 124.7° (SD 27.5°) for AR. Linear range of motion was 255.8 mm (SD 53.5 mm), 217.6 mm (SD 35.7 mm) and 74.7 mm (SD 26.3 mm), respectively, for anteroposterior, lateral and inferior displacements. Assessing rotational and translational mobility of the helmeted head could also support validation of human models, and evaluate how safety devices could restrain head neck mobility before crash. [ABSTRACT FROM AUTHOR]

Objective: This work aims at investigating the influence of some front-end design parameters of a passenger vehicle on the behavior and damage occurring in the human lower limbs when impacted in an accident.Methods: The analysis is carried out by means of finite element analysis using a generic car model for the vehicle and the lower limbs model for safety (LLMS) for the purpose of pedestrian safety. Considering the pedestrian standardized impact procedure (as in the 2003/12/EC Directive), a parametric analysis, through a design of experiments plan, was performed. Various material properties, bumper thickness, position of the higher and lower bumper beams, and position of pedestrian, were made variable in order to identify how they influence the injury occurrence. The injury prediction was evaluated from the knee lateral flexion, ligament elongation, and state of stress in the bone structure.Results: The results highlighted that the offset between the higher and lower bumper beams is the most influential parameter affecting the knee ligament response. The influence is smaller or absent considering the other responses and the other considered parameters. The stiffness characteristics of the bumper are, instead, more notable on the tibia. Even if an optimal value of the variables could not be identified trends were detected, with the potential of indicating strategies for improvement.Conclusions: The behavior of a vehicle front end in the impact against a pedestrian can be improved optimizing its design. The work indicates potential strategies for improvement. In this work, each parameter was changed independently one at a time; in future works, the interaction between the design parameters could be also investigated. Moreover, a similar parametric analysis can be carried out using a standard mechanical legform model in order to understand potential diversities or correlations between standard tools and human models. [ABSTRACT FROM AUTHOR]

Scoliosis is a 3D deformation of the spine and rib cage. For severe cases, surgery with spine instrumentation is required to restore a balanced spine curvature. This surgical procedure may represent a neurological risk for the patient, especially during corrective maneuvers. This study aimed to computationally simulate the surgical instrumentation maneuvers on a patient-specific biomechanical model of the spine and spinal cord to assess and predict potential damage to the spinal cord and spinal nerves. A detailed finite element model (FEM) of the spine and spinal cord of a healthy subject was used as reference geometry. The FEM was personalized to the geometry of the patient using a 3D biplanar radiographic reconstruction technique and 3D dual kriging. Step by step surgical instrumentation maneuvers were simulated in order to assess the neurological risk associated to each maneuver. The surgical simulation methodology implemented was divided into two parts. First, a global multi-body simulation was used to extract the 3D displacement of six vertebral landmarks, which were then introduced as boundary conditions into the personalized FEM in order to reproduce the surgical procedure. The results of the FEM simulation for two cases were compared to published values on spinal cord neurological functional threshold. The efficiency of the reported method was checked considering one patient with neurological complications detected during surgery and one control patient. This comparison study showed that the patient-specific hybrid model reproduced successfully the biomechanics of neurological injury during scoliosis correction maneuvers. [ABSTRACT FROM PUBLISHER]

The present study aims to investigate the influence of various passenger vehicle front-end designs on knee ligaments and tibia injuries of pedestrian lower limbs by finite element simulations. Using a detailed finite element model of the lower limb, this work was focused on tibia fractures and knee ligament ruptures of lower limbs during vehicle–pedestrian impacts. The influences of vehicle front-end structures on the risk of these two injury occurrences were investigated using super mini, small family car, executive car, and multipurpose vehicle passenger vehicle types. The overall results show that the bumper beam design play an important role in inducing pedestrian lower limb injuries. Its height to the road surface, width in the height direction, and the deformable depth between it and the bumper fascia should be all considered in the vehicle design to protect pedestrian lower limbs. [ABSTRACT FROM AUTHOR]

Lateral bending and shearing were considered as principal injury mechanisms to knee joint of pedestrians. This study aims to establish a failure modelling method to predict the injuries of knee ligaments whilst properly considering the complex loading conditions composed of lateral bending and shearing. Due to the specific model characteristics, ultimate strain of tensile loading test could not be implemented directly in the model as strain failure parameters. To obtain the proper strain failure parameters, we firstly established them with the iterative simulations by approaching the global failure strain in the simulation to the ultimate strain reported by the tensile test. Then, these failure parameters were evaluated against the published experimental tests concerning combined lateral bending and shearing loadings as well as pure lateral bending and shearing. Overall results from the finite element simulations showed a good adoptability of the established failure properties for predicting the ligament failures. [ABSTRACT FROM AUTHOR]

To prevent traumas to abdominal organs, the selection of efficient safety devices should be based on a detailed knowledge of injury mechanisms and related injury criteria. In this sense, finite element (FE) simulation coupled with experiment could be a valuable tool to provide a better understanding of the behaviour of internal organs under crash conditions. This work proposes a methodology based on inverse analysis which combines exploration process optimisation and robustness study to obtain mechanical behaviour of the complex structure of the liver through FE simulation. The liver characterisation was based on Mooney–Rivlin hyperelastic behaviour law considering whole liver structure under uniform quasi-static compression. With the global method used, the model fits experimental data. The variability induced by modelling parameters is quantified within a reasonable time. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzes the injury criteria of knee joints under car-pedestrian impact environments. The study uses the finite element simulations to implement a sensitivity analysis of the car-pedestrian impact. Results show that the new injury criterion regarding the complex kinematics of a knee joint under car-pedestrian impact environments can be used for the evaluation and promotion of the design of car-front-end structures for pedestrian safety.