Efficiency of knee braces: A biomechanical approach based on computational modeling.

International audienceThe knee is the largest joint in the body and is vulnerable to injury during athletic activities or to musculoskeletal conditions such as arthrosis. Knee orthotic devices are widely used by physicians as preventive and therapeutic adjuncts for both musculoskeletal conditions and sport injuries. Their goal is to stabilize or restrict non-physiological knee ranges of motion. The efficiency of these devices has been studied both from clinical and biomechanical perspectives, leading to controversial results from questionable methods. As for now, the mechanisms of force transfer from the device to the joint bones have never been characterized and both device manufacturers and clinicians still expect a standard procedure to compare and grade the efficiency of different knee braces. The objectives of this work are: 1. to quantify the mechanical reactions of knee braces against non-physiological movements; 2. to relate these mechanical reactions to the pressure applied by the braces onto the skin. The latter is particularly important because it refers to comfort issues, which play a key role in a patient's compliance to the orthopedic treatment. A Finite Element Model of a braced human leg is developed. The model is first applied for characterizing the behavior of different kinds of knee braces, focusing on the mechanical reactions against non-physiological movements. In the model, a special attention is paid to the interfaces between knee-braces and the skin and between the skin and the muscles. The interface properties of the model are calibrated against experimental data measured by full-field measurements of 3D displacement over the surface of a patient's leg. The results show that the mechanical action of knee braces is essentially limited by skin/fabric and skin/muscles sliding. Finally, the model leads to a better understanding of the knee/brace interaction, and of the role of the brace components on the stability of the injured knee. Thanks to this computational tool, novel brace designs can be tested and evaluated for an optimal mechanical efficiency of the devices. Future work consists in considering the patient's comfort in the approach

Mechanical determinants of 100-m sprint running performance

International audienceSprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force–velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P0.683; P0.21). Last, anthropometric data of body mass index and lowerlimb- to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a ‘‘velocity-oriented’’ force–velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time

Evolution monitoring of a solution-mining cavern in salt : identifying and analysing early-warning signals prior to collapse

International audienceRisk management of underground cavities requires a good working knowledge of accidental phenomena like subsidence or large-scale collapse. This was the context when the opportunity was taken to instrument a large size in use saline cavern, so as to test various auscultation techniques available under controlled conditions. A microseismic monitoring network coupled to a surface measurement system was installed to improve our knowledge of the mechanisms that initiate and govern the evolution of the cavern up to its collapse. After a stationary period combined with partial depressurization tests conducted in 2005 and 2007, the cavern appears to have entered into its final evolution phase, and this probably since early 2008. This results in continuous and highly sustained microseismic activity as well as the occurrence of a number of microseismic episodes localized around the cavern roof. The localization of the microseismic events, for some of these episodes, is closely correlated to the quasi-dynamic brine pressure variations and to the evolutions of the roof depth measured at observation boreholes. The microseismic activity turns out to be more precise when it comes to the evolution affecting the mine cavern than the movement measurements taken on the surface or sub-surface

Risk factors for gallstones and kidney stones in a cohort of patients with inflammatory bowel diseases

Gallstones and kidney stones are known complications of inflammatory bowel diseases (IBD). Risk factors have been insufficiently studied and explanatory studies date back up to 30 years. It remains unclear, whether improved treatment options also influenced risk factors for these complications.Identifying risk factors for gallstones and kidney stones in IBD patients.Using data from the Swiss Inflammatory Bowel Disease Cohort Study we assessed associations of diseases characteristics with gallstones and kidney stones in univariate and multivariate logistic regression analyses.Out of 2323 IBD patients, 104 (7.8%) Crohn's disease (CD) and 38 (3.8%) ulcerative colitis (UC) patients were diagnosed with gallstones. Significant risk factors for gallstones were diagnosis of CD, age at diagnosis, disease activity and duration, NSAID intake, extra-intestinal manifestations and intestinal surgery. Kidney stones were described in 61 (4.6%) CD and 30 (3.0%) UC patients. Male gender, disease activity, intestinal surgery, NSAID usage and reduced physical activity were significant risk factors. Hospitalization was associated with gallstones and kidney stones. The presence of gallstones increased the risk for kidney stones (OR 4.87, p<0.001).The diagnosis of CD, intestinal surgery, prolonged NSAID use, disease activity and duration and bowel stenosis were significantly associated with cholecystonephrolithiasis in IBD

Cancer risk in immune-mediated inflammatory diseases (IMID).

Inflammation and cancer have a profound yet ambiguous relationship. Inflammation - especially chronic inflammation - has protumorigenic effects, but inflammatory cells also mediate an immune response against the tumor and immunosuppression is known to increase the risk for certain tumors.This article reviews current literature on the role of inflammation in cancer and the cancer risk in immune-mediated inflammatory diseases (IMIDs). We discuss the effect on cancer risk of different drug classes used in the treatment of IMIDs treatment, including biologicals such as tumor necrosis factor (TNF) inhibitors.Overall cancer incidence and mortality risk are similar to the general population in inflammatory bowel disease (IBD), and slightly increased for rheumatoid arthritis and psoriasis, with risk profiles differing for different tumor types. Increased risk for non-melanoma skin cancer is associated with thiopurine treatment in IBD, with the combination of anti-TNF and methotrexate in rheumatoid arthritis and with PUVA, cyclosporine and anti-TNF treatment in psoriasis. Data on the safety of using biologic or immunosuppressant therapy in IMID patients with a history of cancer are scarce.This review provides clinicians with a solid background to help them in making decisions about treatment of immune-mediated diseases in patients with a tumor history.This article is related to another review article in Molecular Cancer: http://www.molecular-cancer.com/content/12/1/86.Peer reviewe

Agroforestry for Improving Small-Scale Farm Yield in Volcanic Highlands in Rwanda

This paper attempts to examine the role of agroforestry in improving crop yield of small-scale agriculture in the region of Volcanic Highlands of Rwanda. We conducted a survey to a random sample of 401 crop growers, including 305 agroforestry adopters and 95 non-adopters, selected from the study area. An econometric model that lowers the heterogeneity between the treatment and the control groups was specified and estimated. Results revealed a considerable difference in farm yields between agroforestry practitioners and non-practitioners. The adoption of agroforestry appears to have a good impact on small-scale agricultural yield, even though this effect is not statistically significant. Results also show that factors including farm investment cost, market accessibility, cooperative membership and return of plan leftovers to the soil have a significantly substantial effect on farm productivity. On the other hand, farm experience and cultivated land area have a detrimental but considerable impact on farm productivity. Based on the research findings, governmental institutions and development associates should promote and hasten the adoption of agroforestry structures, start increasing support for agroforestry adoption through proximity to extension services and accessibility of high-quality plant seedlings, support for the sustainability of farm cooperatives along with financial support for enhancing farm investments and guarantee a continuous and increased market access to crop farmers so as to ensure sustainable sources of farm investments

Back to the future of soil metagenomics

JN was funded by a fellowship from the French MENESR.Peer reviewedPeer Reviewe

Understanding the first injury in athletics and its effect on dropout from sport:An online survey on 544 high-level youth and junior athletics (track and field) athletes

Objective To describe the first injury and to investigate whether it plays a role in altering athletics’ sustainable practice.Methods We conducted a cross-sectional study using an exploratory survey on the first injury and its consequences on athletics practice. In 2021, we asked all high-level athletes licensed with the French Federation of Athletics (FFA) under 18 years, under 20 years and under 23 years categories between 2007 and 2021.Results Out of 6560 emails sent by FFA, 544 athletes responded, and 93.6% (n=510) reported experiencing at least one injury during their career. The first injury occurred at a mean age of 17.5±3.3 years after 6.1±4.1 years of athletics practice. The main locations of the first injury were the posterior thigh (28.9%), the ankle (16.5%) and the knee (12.6%), and the principal reported injury types were muscle (37.7%), tendon (17.5%) and ligament (15.5%). More than a third of injured athletes (36.7%) reported experiencing ongoing symptoms or sequelae after their first injury, and about half (48.5%) experienced recurrences. About 20% had stopped athletics at the time of the survey, with injury problems the primary cause of athletes dropping out (46.2%), including the first injury (9.4%).Conclusions Injuries played an important role in altering sustainable athletics practice, with injury accounting for about 50% of all reported dropouts and the first injury accounting for about 10% of all reported causes. Our results provide evidence to target the prevention of the first injury, which could be considered the origin of the ‘vicious circle’ of injuries

Facteurs socioculturels influençant l'utilisation et la gestion des eaux thermales dans la province du Sud-Kivu, en Republique Democratique du Congo (RDC)

Le présent travail a pour objet d’étudier les facteurs limitant l’utilisation et la gestion durable des sources thermales au Sud-Kivu. Il se fixe comme objectifs&nbsp;: - évaluer les facteurs socio-cultures et sanitaires des usagers des eaux thermales, -identifier les croyances entravant la gestion durable de ces eaux, et enfin, -évaluer le niveau d'implication des pouvoirs publics dans la gestion durable des sites thermaux. En plus, il est du type ethnographique consistant à examiner les facteurs socioculturels et institutionnels qui influencent l’utilisation et la gestion des sources thermales dans la province du Sud-Kivu, en RDC. La méthodologie utilisée porte sur une enquête menée dans les six sites thermaux auprès de 380 usagers locaux ciblés et choisis aléatoirement. En outre, la méthode qualitative basée sur les interviews a été utilisée auprès de 4 responsables des institutions publiques ayant en charge la gestion des ressources hydrauliques et la santé au Sud-Kivu. Les données collectées à partir du mois de mai en octobre 2024 ont été analysées grâce au logiciel STATA, ainsi nous avons utilisé le test de Chi² de Pearson pour calculer l’OR, la P-Value, la régression logistique et le test d’ANOVA pour comprendre les liens entre les divers paramètres retenus. L’étude a abouti aux résultats selon lesquels: les femmes sont légèrement majoritaires (50, 3%).Ensuite, les jeunes adultes de 18 à 41 ans prédominent (32,9%), les analphabètes ont un taux élevé (34, 2%).Mais, le test a prouvé que ceux ayant un niveau d'étude élevé sont moins susceptibles d'utiliser les eaux thermales (OR = 0,695, p = 0,016), les agriculteurs prédominent (35,8%) ce qui justifie le caractère rural des sites thermaux étudiés. Quant aux croyances, la perception de l’eau thermale comme un "don de Dieu" ou un "héritage des ancêtres ». Elle est perçue comme des opportunités et des obstacles à la gestion durable des eaux thermales, etc. Le niveau d’implication des institutions publiques est faible par le fait de l'absence d'un cadre réglementaire spécifique, pas de cadre institutionnel et de maintenances inadéquates. &nbsp; The present work aims to study the factors limiting the use and sustainable management of thermal springs in South Kivu. It sets the following objectives: - evaluate the socio-cultural and health factors of thermal water users, - identify the beliefs hindering the sustainable management of these waters, and finally, - assess the level of public authorities' involvement in the sustainable management of thermal sites. Additionally, it is of an ethnographic type, consisting of examining the socio-cultural and institutional factors that influence the use and management of thermal springs in the South Kivu province, in the DRC. The methodology used involves a survey conducted at the six thermal sites with 380 targeted and randomly selected local users. Furthermore, the qualitative method based on interviews was used with 4 officials from public institutions responsible for managing hydraulic resources and health in South Kivu. The data collected from May to October 2024 were analyzed using the STATA software, and we used the Pearson Chi² test to calculate the OR, the P-value, logistic regression, and the ANOVA test to understand the relationships between the various parameters considered. The study concluded with the results indicating that women are slightly in the majority (50.3%). Next, young adults aged 18 to 41 predominated (32.9%), and the illiterate population had a high rate (34.2%). But, the test proved that those with a higher level of education are less likely to use thermal waters (OR = 0.695, p = 0.016), and farmers predominate (35.8%), which justifies the rural character of the studied thermal sites. Regarding beliefs, the perception of thermal water as a "gift from God" or an "inheritance from ancestors." It is perceived as both an opportunity and obstacle to the sustainable management of thermal waters, etc. The level of involvement of public institutions is low due to the absence of a specific regulatory framework, no institutional framework, and inadequate maintenance

Toward CFD-DEM simulations of the blast furnace raceway

Gas injections at the bottom of the blast furnace create void regions in the coke matrix called the raceways which play a role in the gas distribution in the furnace and is directly linked to the iron production. In this region, complex physical phenomena occur, including particle-fluid with combustion, and, to our knowledge, there is no consensus on its shape and dynamics as well as its creation and stability. A better understanding of the raceway region could lead to a more efficient and stable blast furnace process. An unresolved CFD-DEM approach is used to study the gas-solid flows where coke particles are modelled as a discrete phase and the gas as continuous solving the RANS modelling of the turbulence. In order to clarify the main phenomena occurring in the raceway dynamics, we develop a CFD-DEM model of a 1/5 scale 2d slot pilot of the blast furnace for which alternative raceway collapses are monitored. First, DEM simulations are realized without the fluid contribution and shows that the pilot geometry influences the mechanical load applied on the raceway with a saturation of the granular stress inside the pilot. Also, dry raceway collapse shows a modification of this stress in a short characteristic time. Then, CFD-DEM model of the pilot permits to investigate the gas and granular flows when the raceway is imposed as in the experiment. The dynamics of the collapse with the coupling is solved and displays a complex particle-gas 3d flow. Further implementation in the model will allow coke particle combustion