A simple geometrical method to minimise crosstalk during clinical gait analysis

XV International Symposium on 3-D Analysis of Human Movement, MANCHESTER, ROYAUME-UNI, 03-/07/2018 - 06/07/2018Stereophotogrammetry has been widely used for measuring gait. Conventional gait analysis systems tend to be based on the Davis marker-set [1]. This marker-set is dependent on the position of a wand on the thigh to define medial-lateral thigh axis. This wand is supposed to lie in the frontal plane of the thigh and can be difficult to position properly. A poor positioning leads to axis misorientation which can cause errors known as crosstalk. Crosstalk corresponds to an unphysiological knee Abduction Adduction (AA) amplitude correlated with knee Flexion-Extension (FE) [2]. This phenomenon also affects hip Internal External Rotation (IER) which is a parameter of high interest in clinical gait analysis (CGA). Several methods have been proposed previously to better define the medial-lateral axis of the thigh and improve the quality of both hip and knee kinematics. However, the corrections were not always satisfying or difficult to implement [2-3]

Correcting lower limb segment axis misalignment in gait analysis: A simple geometrical method

Background Obtaining precise and repeatable measurements is essential to clinical gait analysis. However, defining the thigh medial-lateral axis segment remains a challenge, with particular implications for the hip rotation profile. Thigh medial-lateral axis misalignment modifies the hip rotation profile and can result in a phenomenon called crosstalk, which increases knee adduction-abduction amplitude artificially. Research question This study proposes an a posteriori geometrical method based solely on segment anatomy that aims to correct the thigh medial-lateral axis definition and crosstalk-related error. Methods The proposed method considers the thigh medial-lateral axis as the normal to the mean sagittal plane of the lower limb defined by hip, knee and ankle joint centres during one gait cycle. Its performance was compared to that of an optimisation method which repositions the axis to reduce knee abduction-adduction variance. An existing dataset was used: 75 patients with a knee prosthesis undergoing gait analysis three months and one-year post-surgery. Three-dimensional hip and knee angles were computed for two gait analysis sessions. Crosstalk was quantified using both the coefficient of determination (r²) between knee flexion-extension and adduction-abduction and the amplitude of knee adduction-abduction. The reproducibility of hip internal-external rotation was also quantified using the inter-trial, inter-session and inter-subject standard deviations and the intraclass coefficient (ICC). Results Crosstalk was significantly reduced from r²?=?0.67 to r²?=?0.51 by the geometrical method but remained significantly higher than with the optimisation method with a r²

Conditional Neural Relational Inference for Interacting Systems

In this work, we want to learn to model the dynamics of similar yet distinct groups of interacting objects. These groups follow some common physical laws that exhibit specificities that are captured through some vectorial description. We develop a model that allows us to do conditional generation from any such group given its vectorial description. Unlike previous work on learning dynamical systems that can only do trajectory completion and require a part of the trajectory dynamics to be provided as input in generation time, we do generation using only the conditioning vector with no access to generation time's trajectories. We evaluate our model in the setting of modeling human gait and, in particular pathological human gait

Supercontinuum generation using continuous-wave multiwavelength pumping and dispersion management

International audienceWe experimentally demonstrate that continuous-wave supercontinuum generation in optical fibers can be significantly enhanced by using both multiwavelength pumping and dispersion management. We show by detailed spectral analysis that continuum enhancement is achieved mainly through a combination of Raman-assisted modulation instabilities, soliton compression, and dispersive wave generation. With this technique, an 800 nm wide (from 1.2 to 2.0 μm) 2 W supercontinuum source is reported that uses a three-wavelength pump and a dispersion-tailored four-optical fibers arrangement

Can the evaluation of marker placement confidence be used as an indicator of gait kinematic variability?

IntroductionThree-dimensional gait analysis is widely used for the clinical assessment of movement disorders. However, measurement error reduces the reliability of kinematic data and consequently assessment of gait deviations. The identification of high variability is associated with low reliability and those parameters should be ignored or excluded from gait data interpretation. Moreover, marker placement error has been demonstrated to be the biggest source of variability in gait analysis and may be affected by factors intrinsic to the evaluators such as the evaluator's expertise which could be appraised through his/her experience and confidence in marker placement.ObjectivesIn the present study, we hypothesized that confidence in marker placement is correlated with kinematic variability and could potentially be used as part of a score of reliability. Therefore, we have proposed a questionnaire to evaluate qualitatively the confidence of evaluators in lower-limb marker placement. The primary aim of this study was to evaluate the reliability and validity of the presented questionnaire. The secondary objective was to test a possible relationship between marker placement confidence and kinematics variability.MethodsTo do so, test-retest gait data were acquired from two different experimental protocols. One protocol included data from a cohort of 32 pathological and 24 asymptomatic subjects where gait analysis was repeated three times, involving two evaluators. A second protocol included data from a cohort of 8 asymptomatic adults with gait analysis repeated 12 times, per participant, and involving four evaluators with a wider range of experience.ResultsResults demonstrated that the questionnaire proposed is valid and reliable to evaluate qualitatively the confidence of evaluators in placing markers. Indeed, confidence scores were correlated with the actual variability of marker placement and revealed the evaluator's experience and the subjects' characteristics. However, no correlation was observed between confidence scores and kinematic variability and the formulated hypothesis was not supported

Antibacterial Resistance, Wayampis Amerindians, French Guyana

Drug resistance in fecal bacteria was high in Wayampis Amerindians who did not take antibacterial agents and were not hospitalized for 1 year. In the Wayampis Amerindians, an isolated traditional community in French Guyana, antibacterial use was 0.64 treatments per person per year. Hospitalization rate was 6.1% per year. Antibacterial drug–resistant bacteria can spread in persons who are not taking antibacterial agents

Segregation between SMCHD1 mutation, D4Z4 hypomethylation and Facio-Scapulo-Humeral Dystrophy: a case report

International audienceBackground: The main form of Facio-Scapulo-Humeral muscular Dystrophy is linked to copy number reduction of the 4q D4Z4 macrosatellite (FSHD1). In 5 % of cases, FSHD phenotype appears in the absence of D4Z4 reduction (FSHD2). In 70-80 % of these patients, variants of the SMCHD1 gene segregate with 4qA haplotypes and D4Z4 hypomethylation.Case presentation: We report a family presenting with neuromuscular symptoms reminiscent of FSHD but without D4Z4 copy reduction. We characterized the 4q35 region using molecular combing, searched for mutation in the SMCHD1 gene and determined D4Z4 methylation level by sodium bisulfite sequencing. We further investigated the impact of the SMCHD1 mutation at the protein level and on the NMD-dependent degradation of transcript. In muscle, we observe moderate but significant reduction in D4Z4 methylation, not correlated with DUX4-fl expression. Exome sequencing revealed a heterozygous insertion of 7 bp in exon 37 of the SMCHD1 gene producing a loss of frame with premature stop codon 4 amino acids after the insertion (c.4614-4615insTATAATA). Both wild-type and mutated transcripts are detected.Conclusion: The truncated protein is absent and the full-length protein level is similar in patients and controls indicating that in this family, FSHD is not associated with SMCHD1 haploinsufficiency

Nouveaux restes humains moustériens rapportés au squelette néandertalien de Regourdou 1 (Regourdou, commune de Montignac, Dordogne, France)

Le présent article fait état de la découverte de nouveaux ossements néandertaliens issus des collections fauniques du site moustérien de Regourdou. Après une présentation du gisement situant rapidement le cadre chrono-culturel, l’accent est mis sur l’aspect historiographique, rappelant les travaux de Roger Constant, la découverte de la sépulture néandertalienne « Regourdou 1 » en 1957, les fouilles qui suivirent, et les mouvements des vestiges découverts. Ces précisions montrent que le contexte n’a pas joué en faveur de la préservation idéale du matériel exhumé. Pour preuve, des travaux de récolement et une étude en cours ont permis d’isoler plusieurs ossements humains parmi les vestiges fauniques acquis en 2002 par le Musée national de Préhistoire. Ils sont a priori tous attribuables à la sépulture qu’ils complètent de façon significative. Ces pièces sont issues de la couche 4 qui a livré la sépulture humaine, mais elles ne sont pas toutes à rapporter au “tumulus” ivA auquel correspond cette sépulture. Les caractéristiques anatomiques de ces nouvelles pièces mettent en évidence leur appartenance soit au squelette Regourdou 1 soit à la lignée néandertalienne. Le squelette original Regourdou 1, découvert en 1957, présentait un contraste très net entre la présence de deux chaînes articulaires assez complètes pour les membres supérieurs et la quasi-absence de restes pour les membres inférieurs, en dehors des pieds. Les nouvelles découvertes viennent, en partie, combler ce manque. Des travaux plus approfondis sur chacune des pièces nouvellement identifiées complèteront nos connaissances de la variabilité du squelette infra-crânien des Néandertaliens, Regourdou 1 devenant un des squelettes moustériens les plus complets mis au jour dans le sud-ouest de la France. Quant à l’absence totale du calvarium, compte-tenu du contexte général, il faut peut-être aussi envisager une nouvelle hypothèse selon laquelle il se trouverait encore au sein du remplissage sédimentaire non fouillé du site