13 research outputs found
Chondrocyte Deformations as a Function of Tibiofemoral Joint Loading Predicted by a Generalized High-Throughput Pipeline of Multi-Scale Simulations
Cells of the musculoskeletal system are known to respond to mechanical loading and chondrocytes within the cartilage are not an exception. However, understanding how joint level loads relate to cell level deformations, e.g. in the cartilage, is not a straightforward task. In this study, a multi-scale analysis pipeline was implemented to post-process the results of a macro-scale finite element (FE) tibiofemoral joint model to provide joint mechanics based displacement boundary conditions to micro-scale cellular FE models of the cartilage, for the purpose of characterizing chondrocyte deformations in relation to tibiofemoral joint loading. It was possible to identify the load distribution within the knee among its tissue structures and ultimately within the cartilage among its extracellular matrix, pericellular environment and resident chondrocytes. Various cellular deformation metrics (aspect ratio change, volumetric strain, cellular effective strain and maximum shear strain) were calculated. To illustrate further utility of this multi-scale modeling pipeline, two micro-scale cartilage constructs were considered: an idealized single cell at the centroid of a 100×100×100 μm block commonly used in past research studies, and an anatomically based (11 cell model of the same volume) representation of the middle zone of tibiofemoral cartilage. In both cases, chondrocytes experienced amplified deformations compared to those at the macro-scale, predicted by simulating one body weight compressive loading on the tibiofemoral joint. In the 11 cell case, all cells experienced less deformation than the single cell case, and also exhibited a larger variance in deformation compared to other cells residing in the same block. The coupling method proved to be highly scalable due to micro-scale model independence that allowed for exploitation of distributed memory computing architecture. The method’s generalized nature also allows for substitution of any macro-scale and/or micro-scale model providing application for other multi-scale continuum mechanics problems
The surface electromyography analysis of the non-plegic upper limb of hemiplegic subjects Análise da eletromiografia de superfĂcie do membro superior nĂŁo plĂ©gico de hemiplĂ©gicos
Many authors have studied physical and functional changes in individuals post-stroke, but there are few studies that assess changes in the non-plegic side of hemiplegic subjects. This study aimed to compare the electromyographic activity in the forearm muscles of spastic patients and clinically healthy individuals, to determine if there is difference between the non-plegic side of hemiplegics and the dominant member of normal individuals. 22 hemiplegic subjects and 15 clinically healthy subjects were submitted to electromyography of the flexor and extensor carpi ulnaris muscles during wrist flexion and extension. The flexor muscles activation of stroke group (average 464.6 u.n) was significantly higher than the same muscles in control group (mean: 106.3 u.n.) during the wrist flexion, what shows that the non affected side does not present activation in the standart of normality found in the control group.<br>Muitos autores estudaram as modificações funcionais e fĂsicas em indivĂduos pĂłs-acidente vascular cerebral; porĂ©m, poucos estudos avaliam alterações no hemicorpo nĂŁo plĂ©gico de indivĂduos hemiplĂ©gicos. O objetivo deste estudo foi comparar a atividade eletromiográfica nos mĂşsculos do antebraço de pacientes espásticos e indivĂduos clinicamente saudáveis, para averiguar se há diferença entre o lado nĂŁo plĂ©gico de indivĂduos hemiplĂ©gicos e o lado dominante de indivĂduos clinicamente saudáveis. 22 indivĂduos hemiplĂ©gicos e 15 clinicamente saudáveis foram submetidos Ă eletromiografia dos mĂşsculos flexor e extensor ulnar do carpo durante a flexĂŁo e extensĂŁo do punho. A ativação dos mĂşsculos flexores dos hemiplĂ©gicos (mĂ©dia: 464,6 u.n), foi significantemente maior que nos indivĂduos do grupo controle (mĂ©dia: 106,3 u.n) durante o movimento de flexĂŁo do punho, o que demonstra que o hemicorpo nĂŁo acometido dos pacientes estudados nĂŁo apresenta o comportamento padrĂŁo de normalidade encontrado no grupo controle