Academic literature on the topic 'Flexion-torsion combinées'

The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-samplet-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location.

Introduction. One of the complications of the clinical course of cerebral palsy in children is external torsion of the tibia. The issue of localization and the mechanism of its formation, as well as effective methods of its elimination, is debatable. Purpose - to study the mechanisms of the formation of pathological external torsion of the tibia in children with cerebral palsy, its effect on knee joint contracture and foot deformity, and effective methods of their correction. Materials and methods. The data obtained during the observation of 45 patients (90 cases) aged from 6 to 16 years with spastic diplegia, spastic tetraparesis and foot pronation were analyzed. To study the mechanisms of formation of external torsion of the lower leg and its correction, 2 groups of patients were selected. The Group I - 24 patients with internal rotation contractures of the hip joint (10 patients with internal rotation contractures of the hip joint; 10 patients - in combination with pathological antetorsion of the femoral neck; 4 patients - in combination with flexion contractures of the knee joints). The relationship between internal rotation contracture of the hip joint and external torsion of the tibia. The Group II consisted of 21 patients who were diagnosed with flexion contracture of the knee joints in combination with external torsion of the tibia. In order to study the effectiveness of operative treatment of knee flexion contracture and external torsion of the tibia in the Group II, 2 subgroups were distinguished: the subgroup IIA - 9 patients who underwent osteotomy of the tibial bone; the subgroup IIB - 12 patients who only underwent biceps femoris transposition. Results. Based on the study of clinical and radiological indicators, it was established that pathological torsion of the tibial bone is combined with flexion contracture of the knee joints. Proximal derotational osteotomy of the tibia has a positive effect on the results of correction of knee flexion contracture and foot position. Conclusions. The main reason for the formation of external torsion of the tibia is the imbalance of the flexor muscles of the knee joint and the supinator and pronator muscles of the foot. Proximal tibial derotation osteotomy eliminates not only pathological torsion, but also flexion contracture of the knee joints and excessive pronation of the foot. The study was conducted in accordance with the principles of the Declaration of Helsinki. The study protocol was approved by the local ethics committees of all institutions participating in the study. Informed consent of the patients was obtained for the research. No conflict of interests was declared by the authors.

Abstract Background and Purpose. The purpose of this study was to assess the association between innominate torsion (asymmetric anteroposterior positioning of the pelvic innominates) and the Gillet, standing forward flexion, sitting forward flexion, and supine-to-sit tests. Subjects. A sample of 21- to 50-year-old patients with low back pain (n=150) and a comparison group of patients with upper-extremity impairments (n=138) were recruited from outpatient physical therapy facilities. Methods. The association of single and combined test results with innominate torsion (calculated from pelvic landmark data) and with presence or absence of low back pain were estimated via odds ratios, sensitivities, specificities, and predictive values. Results. Individual test sensitivities were low (8%-44%), as were negative predictive values (28%-38%), for identifying the presence of innominate torsion. Combining tests and controlling for sex, age group, leg-length difference, or iliac crest level did not improve performance characteristics. The associations of test results with low back pain were weak, with the exception of the Gillet test (odds ratio=4.57). Conclusion and Discussion. The data do not support the value of these tests in identifying innominate torsion, although the use of these tests for identifying other phenomena (eg, sacroiliac joint hypomobility) cannot be ruled out. Further exploration of the association of Gillet test results with low back pain is warranted.

This paper addresses the role of torsion in the production of spinal injury and in particular the possibility of injury resulting from torsion combined with flexion. The back movement of 16 normal male subjects was measured using a non-invasive, three-dimensional measurement system for assessing spinal mobility, the opto-electronic CODA-3 scanner. Measurements were made of the ability to twist the back while standing upright and in two flexed postures. Rotational ability was shown, in general, to be increased in a flexed posture, presumed to be due to an opening of the lumbar zygapophysial joints. This suggests that twisting in a flexed posture could be a mechanism for intervertebral disc injury.

Based on tension-compression and bending equivalences, an equivalent single material plate is formed to substitute bridge deck of composite girder with steel fiber reinforced concrete (SFRC) and steel. Thickness and elastic modulus of the equivalent plate are then formulated. After three dimensional finite-element analyses of the bridge deck, in terms of shell element membrane effect and girder flexion-torsion theory, combined with compatibility of deformation, single material shell element stress is restored to stresses on SFRC plate and steel plate separately; shear force distribution on shear keys between SFRC and steel is analyzed.

Background. Lower extremity analysis for preoperative total knee and hip arthroplasty routines can increase surgery success rate and hence reduce associated costs. Current tools are limited by being invasive, limited to supine analysis, or too expensive. This study aimed to propose and validate a device, OrthoPilot®, based on the combined use of a stereophotogrammetric and ultrasound system which can in vivo and noninvasively measure varus/valgus, flexion/extension, femur and tibia torsion, and femur and tibia lengths.Methods. A phantom was measured by four operators to determine the resolution of the system. Interoperator variability was measured on three operators who measured the above six variables on both legs of three subjects in standing and supine positions. Intraoperator variability was assessed on data from three repeats from 9 subjects (18 legs).Results. All 6 variables were reliably detected on a phantom, with a resolution of 1 mm and 0.5°. Inter- and intraoperator consistency was observed for varus/valgus, flexion/extension, and length measurements on the healthy subjects in standing and supine positions (all ICC > 0.93). For torsion measurements, there was a considerable variation.Conclusion. The proposed system, when used on healthy subjects, allowed reliable measurements of key parameters for preoperative procedures in both supine and standing positions. Accuracy testing and further validation on patient populations will be the next step toward its clinical adoption.

Intervertebral disc (IVD) degeneration is inadequately understood due to the lack of in vitro systems that fully mimic the mechanical and biological complexity of this organ. We have recently made an advancement by developing a bioreactor able to simulate physiological, multiaxial IVD loading and maintain the biological environment in ex vivo IVD models [1].To validate this new bioreactor system, we simulated natural spine movement by loading 12 bovine IVDs under a combination of static compression (0.1 MPa), cyclic flexion/extension (±3˚, ±6˚ or 0-6˚) and cyclic torsion (±2˚, ±4˚ or 0-4˚) for more than 10’000 (0.2 Hz) or 100’000 (1 Hz) cycles over 14 days. A higher number of cycles increased the release of glycosaminoglycans and nitric oxide, as an inflammation marker, whereas fewer cycles maintained these two factors at physiological levels. All applied protocols upregulated the expression of MMP13 in the outermost annulus fibrosus (AF), indicating a collagen degradation response. This was supported by fissures observed in the AF after a longer loading duration. Increasing loading cycles induced high cell death in the nucleus pulposus and inner AF, while with fewer cycles, high cell viability was maintained in all IVD regions, irrespective of the magnitude of rotation.Less frequent multiaxial loading maintains IVD homeostasis while more frequent loading initiates an IVD degenerative profile. Specifically, the morphological and molecular changes were localized in the AF, which can be associated with combined flexion/extension and torsion. More loading cycles induced region-specific cell death and a higher release of extracellular matrix molecules from the innermost IVD regions, likely associated with longer exposure to static compression. Altogether, we demonstrated the advantages of the multiaxial bioreactor to study region-specific response in the IVD, which will allow a more profound investigation of IVD degeneration under different combinations of motions.

An innovative wearable upper-limb power-assist exoskeleton system (UPES) was designed for laborers to improve work efficiency and reduce the risk of musculoskeletal disorders. This novel wearable UPES consists of four joints, each comprising a single actuated pneumatic muscle actuator (PMA) and a torsion spring module driven via a steel cable. Unlike most single-joint applications, where dual-PMAs are driven by antagonism, this design aims to combine a torsion spring module with a single-PMA via a steel cable for a 1-degree of freedom (1-DOF) joint controlled by a proportional-pressure regulator. The proposed four driving degrees of freedom wearable UPES is suitable for power assistance in work and characterizes a simple structure, safety, and compliance with the motion of an upper limb. However, due to the hysteresis, time-varying characteristics of the PMA, and non-linear movement between joint flexion and extension, the model parameters are difficult to identify accurately, resulting in unmeasurable uncertainties and disturbances of the wearable UPES. To address this issue, we propose an improved proxy-based sliding mode controller integrated with a linear extended state observer (IPSMC-LESO) to achieve accurate power-assisted control for the upper limb and ensure safe interaction between the UPES and the wearer. This control method can slow the underdamped dynamic recovery motion to tend the target trajectory without overshoots from large tracking errors that result in actuator saturation, and without deteriorating the power assist effect during regular operation. The experimental results show that IPSMC-LESO can effectively control a 4-DOF wearable UPES, observe the unknown states and total disturbance online of the system, and adapt to the external environment and load changes to improve system control performance. The results prove that the joint torsion spring module combining the single-PMA can reduce the number of PMAs and proportional-pressure regulators by half and obtain a control response similar to that of the dual-PMA structure.

Les dernières avancées réalisées dans le domaine de l’instrumentation canalaire ont permis de rendre le traitement endodontique plus rapide et plus efficace. L’amélioration des limes endodontiques au travers des géométries instrumentales, mouvement de travail ou propriétés mécaniques du matériau constitutif de l’instrument ont rendu le traitement plus sûr dans la préservation de l’organe dentaire et des tissus parodontaux environnants. Néanmoins, peu de recherches se sont portées sur l’utilisation d’Alliage à Mémoire de Forme (AMF) différents du Nickel-Titane (Ni-Ti). Ce travail se propose d’étudier une potentielle utilisation en endodontie d’un nouvel AMF doté de propriétés antimicrobiennes très prometteuses : le Cuivre-Aluminium-Béryllium (Cu-Al-Be) monocristallin. Cette étude se fait au travers d’une approche expérimentale, au moyen d’un dispositif d’essais innovant, capable d’appliquer des chargements combinés ou séparés de flexion et de torsion. Ces chargements sont les principales sollicitations appliquées aux limes endodontiques lors du traitement canalaire. Une approche numérique vient compléter les études expérimentales, avec un modèle éléments-finis représentatif des chargements appliqués par le dispositif d’essais. Un programme de génération de modèles géométriques de limes endodontiques est développé et permet de représenter les réponses obtenues expérimentalement à l’aide de deux lois de comportement thermomécaniques adaptées aux AMF polycristallins et monocristallins. Enfin, à l’aide de ces deux outils, un plan d’expérience capable de déterminer l’influence des paramètres géométriques d’une lime endodontique sur sa réponse mécanique est réalisé et apporte une aide précieuse à la décision pour le choix d’une géométrie et d’une utilisation adaptée pour ces limes endodontiques en Cu-Al-Be monocristallin
Recent enhancements in canal instrumentation area have significantly improved the endodontic treatment making it faster and more efficient. The improvement of endodontic file quality through the instrument geometry, operating motion, and material properties made the endodontic treatment safer and thereby preserving the tooth and the surrounding periodontal tissues. Nevertheless, few research works investigated the possibility of using an alternative shape memory alloy (SMA) to the Nickel-Titanium (NiTi). This PhD work focuses on investigating the possibility of use in endodontic of Cu-based SMA having promising antimicrobial properties I.e. the Copper-Aluminum-Beryllium (Cu-Al-Be) single crystal SMA. The present study is based on an experimental approach using an original testing device able to apply bending and torsion loading in separate or combined way. Such solicitations are mainly induced by the curvature of the dental canal while the mechanical preparation. A numerical approach completes this experimental part by considering a finite element model representative of the file geometry, the thermomechanical behavior of the Cu-based single crystal or NiTi polycrystal SMAs and the bending- torsion loading and boundary conditions. A developed numerical tool allowed to build a parametrized geometry of an endodontic file and mesh it with tetrahedral finite elements in order to numerically analyze its response under combined bending-torsion loading. Based on these two approaches, an experience plan was carried out in order to analyze the influence of geometrical parameters on the response of endodontic files made of Cu-based single crystal SMA. It could be a precious tool for decision aid in choosing endodontic file geometry and its adapted use for root canal preparation