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Background: Cranial cruciate ligament rupture (CCLr) is the most common cause of hind limb lameness in dogs. Currently, surgical management of CCLr is mostly performed using tibial osteotomy techniques to modify the biomechanical conformation of the affected stifle. These surgical techniques have a significant complication rate, associated with persistent instability of the stifle which may lead to chronic postoperative pain. Over the last decade, studies have been published on various techniques of anatomical caudal cruciate ligament reconstruction in veterinary practice, using physiological autografts or woven synthetic implants. Aim: The aim of this ex vivo biomechanical study is to investigate the ex vivo dynamic biomechanical behavior of a synthetic implant ultrahigh molecular weight polyethylene (UHMWPE) implant fixed with interference screws for the treatment of CCLr in dogs, according to a fatigue protocol (48 hours per test). Methods: Seven stifles from four skeletally mature canine cadavers were implanted with the synthetic implant. It was fixed with four interference screws inserted in transversal and oblique tunnels in both the distal femur and the proximal tibia. For each case, 100,000 cycles were performed at 0.58 Hz, with traction loads ranging from 100 to 210 N. Results: Neither screw-bone assembly rupture nor a pull-out issue was observed during the dynamic tests. Linear stiffness of the implants associated with a fixation system with four interference screws increased over time. The final displacement did not exceed 3 mm for five of the seven specimens. Five of the seven synthetic implants yielded to a lengthening in functional range (0–3 mm). Linear stiffness was homogeneous among samples, showing a strong dynamic strength of the interference screw-based fixations of the UHMWPE implant in the femoral and tibial bones. Conclusion: This study completes the existing literature on the biomechanical evaluation of passive stifle stabilization techniques with a testing protocol focused on cyclic loading at a given force level instead of driven by displacement. These biomechanical results should revive interest in intra-articular reconstruction after rupture of the CCLr in dogs.

Nicolas Giraud conference paper presented at the 46th Congress of the Soci��t�� de Biom��canique (2021)., {"references":["Blanc Q, Goin B, Rafael P, Moissonnier P, Carozzo C, Buttin P, Cachon T, Viguier E. 2019. Effect of the number of interference screws for the fixation of an intraarticular cranial cruciate ligament prosthesis in dogs: Biomechanical study. Comput Methods Biomech Biomed Engin. 22(sup1):S102–S104.","Goin B, Rafael P, Blanc Q, Cachon T, Buttin P, Carozzo C, Chabrand P, Viguier E. 2019. Biomechanical analysis of a ligament fixation system for CCL reconstruction in a canine cadaver model. Comput Methods Biomech Biomed Engin. 22(sup1):S109–S111.","Hayashi K, Manley PA, Muir P. 2004. Cranial cruciate ligament pathophysiology in dogs with cruciate disease: a review. J Am Anim Hosp Assoc. 40(5):385–390.","Krotscheck U, Nelson SA, Todhunter RJ, Stone M, Zhang Z. 2016. Long term functional outcome of tibial tuberosity advancement vs. tibial plateau leveling osteotomy and extracapsular repair in a heterogeneous population of dogs: long term outcome of TTA in dogs. Vet Surg. 45(2):261–268.","von Pfeil DJF, Kowaleski MP, Glassman M, Dejardin LM. 2018. Results of a survey of veterinary orthopedic society members on the preferred method for treating cranial cruciate ligament rupture in dogs weighing more than 15 kilograms (33 pounds). J Am Vet Med Assoc. 253(5): 586–597.","Rafael P, Goin B, Buttin P, Cachon T, Viguier E. 2020. Comparison of two methods of fixation with interference screw for cranial cruciate ligament reconstruction in canine cadaver model. Comput Methods Biomech Biomed Engin. 23(sup1):S247–S249.","Smith PA, Bozynski CC, Kuroki K, Henrich SM, Wijdicks CA, Cook JL. 2019. intra-articular biocompatibility of multistranded, long-chain polyethylene suture tape in a canine ACL model. J Knee Surg. 32(6):525–531."]}

Colloque avec actes et comité de lecture. Internationale.; International audience; Vehicle Restraint Systems (VRS) are specially designed to restrain an errant vehicle by dissipating or absorbing the impact energy and redirecting the vehicles to reduce crash accident severity and protect the roadside equipment. Before being installed on the roadside, a VRS must be tested by crashing with vehicles to evaluate its performances for severity reduction in traffic accident. Europe Norm, EN1317, normalized the crash test conditions, and defined the qualitative and quantitative performance criteria of the device. Dynamic simulation of the crash test has been used for development of new VRS. Uncertainties exist in the VRS: a crash test of the VRS can't be repeated even under the same impact condition; as for the numerical simulations, in fact a model cannot be validated to ?have simulated the crash test accurately'; what's more, uncertainty is inevitable and it may significantly influence the reliability or robustness of a design. The crash test of a steel VRS has been carried out by LIER-TRANSPOLIS according to the norm EN1317. Considering the existence of uncertain factors, the device is optimized with Multi-Objective Non-deterministic Optimization (MONO) approach. The challenges for MONO of complex engineering systems such as the VRS include: high calculation cost of model simulation; numerous uncertain factors. In the previous studies: The crash test of VRS was simulated by LS-DYNA with a simplified VRS & Vehicle model. The numerical model has been used for Sensitivity Analysis (SA) of the VRS: uncertainties in mechanical properties of material, in tolerances of fabrication, in installation conditions of the device were considered and eleven uncertain factors were chosen. SA helps to identity the factors whose uncertainties have great influence on the robustness of the VRS. The two influential uncertain factors were identified and their influences were quantified after the SA. The MONO of the VRS will be discussed in the article: The ?objectives' of the optimization are to increase the capability of the VRS in reducing crash accident severity, and in the same time to minimize the deformation of the VRS during the crash process; Dimensions of the VRS components are chosen as the ?design variables' Robustness of the VRS is mainly influenced by the two influential uncertain factors identified after the SA. Considering influences of the two uncertain factors, along with the mass of device (i.e. cost of production), the robustness of the device are defined as the constraints of the design; Kriging interpolation is used to create the surrogate model of the crash test. Genetic Algorithm is used for the multi-objective optimization; Generalization of impact conditions: the device is optimized under the impact condition specified by EN1317. Performances of the optimized design are evaluated under different impact conditions. Simulations considering the variations of the uncertain factors help to evaluate the robustness of a design and give a cloud of results in which the result of an experimental test could be contained; SA helps to identity the influential uncertain factors; with robustness of the device defined as the constraints of design, the non-deterministic approach optimized the performances of the VRS with their variations controlled under the defined thresholds; the norm EN1317 provides a guideline for the design of VRS, robust analysis and generalization analysis provide useful information about the performance of a design and the norm EN1317 could be enriched.

1st International Conference of Impact Loading of Materials and Structures (ICILSM), TURIN, ITALIE, 22-/05/2016 - 26/05/2016; Motorcyclists' collisions with roadside barriers accident have a high rate of mortality throughout the world. On the European level, there are no standards for assessing the performance of motorcyclist vehicle restraint systems. Two procedures are adopted by most of EU countries: LIER procedure and normative procedure TS1317-8. Both recommend similar conditions of barriers performance testing. In this paper, the test conditions of the two procedures have been assessed by a virtual testing method developed under the explicit finite element code LS DYNA. The main objective of this work is to make propositions about a reference test conditions of which can lead to a future European Standard for the assessment of motorcyclist vehicle restraint systems performance. Then, a full factorial design of experiments (DOE) was used to analyse the impact configurations, the impact point, the impact height, the impact velocity and impact angle influences on motorcycle roadside barrier performance. The DOE variables responses are head, neck and thorax injury index measured on Hybrid III 50th percentile dummy for lateral impact configurations. According to injury index, critical scenarios of motorcyclists' impacts against the infrastructure have been analysed.

More than 1 million people die in crashes on the world’s roads and many millions are seriously injured each year. According to the studies: Run-Off-Road accidents (ROR), i.e. the vehicle run-off the road into the roadside and has at least one collision with either roadside equipment or the roadside itself, “represent about 10% of the total road accidents, while 45% of all fatal accidents are ROR”. Vehicle Restraint Systems (VRS) are the infrastructures installed on the road to provide a level of containment for an errant vehicle. Safety barrier is “continuous VRS installed alongside, or on the central reserve, of a road to prevent errant vehicles from crashing on roadside obstacles, and to retain them safely”. Statistic results show that “the existence of protective barriers on road can reduce fatalities up to a factor of 4 when compared to collisions against other road obstacles.” The life-saving performances of a VRS depend on the design of the device. Standards such as EN1317 normalized the impact conditions under which a design of VRS must be tested by crash tests, and defined the criteria for performance evaluation of a design. While a VRS cannot really be optimized: Multi-criteria exist for performance evaluation of a VRS and all the criteria cannot be optimized in the same time; the impact conditions of the VRS with the errant vehicle are numerous; uncertain factors of the VRS may degrade the performances of a design. The thesis aims to define an approach that can serve: sensitivity analysis (SA) and robust design of the VRS; Enrichment for the existing standards in the design of VRS. The case of a safety barrier is specified in the study: a safety barrier has been test experimentally, the program Ls-Dyna was used for crash simulation of the device; considering properties of the crash model, efficiencies of different SA methods were studied and influences of the critical factors whose uncertainties contribute the most to the instability of the barrier were quantified with the selected SA approaches; considering the uncertainties of the critical factors, Multi-Objective robust optimization of the tested barrier were realized; under different impact conditions, crash simulations of the optimized barrier were carried out to evaluate its performances in the real crash accidents. The approaches presented in the article can be useful for the design of other VRS or more broadly, other complex engineering systems. Hopefully, the robustness analysis and generalization analysis (i.e. performance evaluation of the VRS under different impact conditions) of the safety barrier could enrich the standards for the design of VRS, Plus d'un million de personnes meurent dans des accidents sur les routes du monde et beaucoup de millions sont gravement blessés chaque année. Selon les études, ‘Run-Off-Road accidents (ROR)’, c'est-à-dire que le véhicule a au moins une collision avec des équipements routiers, représentent environ 10% des accidents routières, mais 45% de tous les accidents mortels sont des ROR. Les dispositifs de retenue des véhicules (DDR) sont les infrastructures installées sur la route pour fournir un niveau de confinement du véhicule ‘hors de contrôle’. La barrière de sécurité routière est un DDR continu installé à côté ou sur la réserve centrale d'une route pour empêcher les véhicules errants de s'écraser sur les obstacles routiers et de les conserver en toute sécurité. Les résultats statistique montrent que l'existence des barrières peut réduire les morts jusqu'à un facteur de 4 par rapport aux collisions contre d'autres obstacles routiers. Les performances de sauvetage d'un DDR dépendent de la conception de l'appareil. Des normes telles que EN1317 ont normalisé les conditions des essais de chocs sous lesquelles une conception de DDR doit être testée et ont défini les critères pour l'évaluation des performances d'une conception. En fait, un DDR ne puisse pas vraiment être optimisé: il existe des critères multiples pour l'évaluation de la performance d'un DDR et tous les critères ne peuvent pas être optimisés en même temps; les conditions de travail d’un DDR, c'est-à-dire les conditions d'impact d’un DDR avec un véhicule errant, sont nombreuses; les facteurs incertains du DDR peuvent dégrader les performances d'une conception. La thèse vise à définir une approche qui peut servir : l'analyse de sensibilité (AS) et la conception robuste du DDR ; enrichissement des normes existantes dans la conception du DDR. Le cas d'une barrière de sécurité routière est spécifié dans l'étude : une barrière a été testée expérimentalement, le programme Ls-Dyna est utilisé pour la simulation de choc de l'appareil ; en tenant compte des propriétés du modèle de choc, les efficacités de différentes méthodes de l’AS ont été étudiées ; les influences des facteurs critiques dont les incertitudes contribuent le plus à l'instabilité de la barrière ont été quantifiées avec les approches d’AS sélectionnées ; compte tenu des incertitudes des facteurs critiques, l’optimisation robuste de multi-objectif de la barrière est réalisée ; des simulations d'impact de la barrière optimisée ont été effectuées sous des conditions d'impact différentes pour évaluer ses performances dans les véritables accidents. Les approches présentées dans l'article peuvent être utiles pour la conception d'autres DDR ou plus largement d'autres systèmes d'ingénierie complexes. On peut espérer que l'analyse de robustesse et l'analyse de la généralisation (c'est-à-dire l'évaluation de la performance du DDR sous différentes conditions d'impact) du DDR pourraient enrichir les normes de la conception des DDR