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Identification des propriétés mécaniques des tissus constitutifs du mollet pour l'étude mécanique de la contention

Abstract : Elastic compression is the process of applying external compression forces onto the human leg with stockings or socks, for enhancing the venous flow. Sales of stockings have increased drastically for the past decade. Particularly, compression socks have been released by the BVSport Company for improving muscular recovering after efforts. These socks are based on the principle of progressive compression, which means that the largest pressures are applied onto the calf muscle and not at the ankle. The efficiency of this principle is about to be validated also for treating venous pathologies, which is very promising. The recent developments tend towards patient specific medical prescriptions: socks have to be adapted to the various level of venous insufficiency and to the patient internal morphology. However, no study has already been achieved for determining what the effective pressure applied onto a given patient by socks is, neither in the muscular tissues, nor in the deep venous system. The main contribution of this work lies in implementing a methodology addressing this issue. For that, the patient specific mechanical properties of the tissues in the leg have to be identified, in an atraumatical and non-invasive way. In vivo characterization of soft biological tissues is scarce in the literature (focused mainly on skin) because no atraumatic method has ever been validated for measuring the deformation of soft tissues. In this work, progressive compression socks are employed for loading the tissues in compression. MRI scans of the leg are acquired under several levels of compression. A FE model of the leg under compression has been developed in 2D, with the assumption of plane strains. The boundary conditions are applied as a non uniform pressure, depending on local curvature radii according to the Laplace's law. The applied pressure also depends on the tension of the socks, which is determined by specific tensile tests. The deformation of the leg which is derived from the 2D FE model is used for warping the images provided by the MRI scanner. The mechanical properties of the tissues are identified by optimizing the deviation between the original image of the compressed leg and the warped image, which depends on the mechanical properties input in the model. Finally, when the mechanical properties of the biological tissues are identified, the 2D numerical model is used for computing the pressure applied by the socks inside the leg. This computation can be considered as patient specific because the model has been calibrated against the images of the given patient. The pressure is eventually compared to the pressure prescribed by physicians. It has been shown that the action of socks strongly depends on the leg morphology (muscle properties, thickness of subcutaneous fat). The methodology developed in this study is now to be applied to a significant number of patients, through a clinical study, in order to analyze the effect of the patient morphology onto the efficiency of elastic compression.
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Submitted on : Monday, September 7, 2009 - 10:28:49 AM
Last modification on : Wednesday, June 24, 2020 - 4:18:51 PM
Long-term archiving on: : Tuesday, June 15, 2010 - 8:02:23 PM

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  • HAL Id : tel-00413797, version 1

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L. Bouten. Identification des propriétés mécaniques des tissus constitutifs du mollet pour l'étude mécanique de la contention. Mécanique [physics.med-ph]. Ecole Nationale Supérieure des Mines de Saint-Etienne, 2009. Français. ⟨tel-00413797⟩

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