Résultats à 10 ans de recul moyen de 124 ostéotomies tibiales de valgisation d ouverture médiale fixées par une cale de Biosorb ® et une plaque vissée

L objectif de ce travail était d une part, d évaluer les résultats à long terme de l ostéotomie tibiale de valgisation (OTV) d ouverture médiale et d autre part, d évaluer la tolérance et l intégration de la cale de Biosorb (Phosphate tricalcique ß, SBM, Lourdes). La série était composée de 124 genoux chez 110 patients, 74 hommes et 36 femmes, âgés en moyenne de 53,23+/-10,68 ans (32-74) et opérés entre juin 1995 et décembre 2000 d une arthrose fémoro tibiale médiale par le plus ancien des auteurs. Le score fonctionnel pré-opératoire selon Lysholm et Tegner était en moyenne de 65,44+/-13,32 points (27-80) et l angle HKA pré-opératoire était en moyenne de 172,51+/-3,8 (162-179). Il s agissait, selon la classification d Ahlbäck modifiée de 27 stades I, 42 stades II, 44 stades III et 11 stades IV. Tous les patients ont été revus cliniquement et radiologiquement au recul moyen de 10,39+/-1,98 ans (8-14 ans). Parmi les complications immédiates nous avons colligé 9 refends du plateau tibial latéral sans aucune conséquence, 2 phlébites et 3 embolies pulmonaires régressives après traitement approprié, 3 retards de cicatrisation. À un stade plus tardif nous avons retrouvé 7 retards de consolidation sans aucune pseudarthrose, 3 ruptures de vis sur plaque en T de l instrumentation AO dont une qui a conduit à une perte angulaire secondaire ayant nécessité une reprise par ostéotomie fémorale. L OTV reste une bonne alternative pour le traitement de l arthrose fémoro-tibiale médiale du sujet jeune. La cale de Biosorb® est un excellent substitut osseux pour le comblement des ostéotomies tibiales d addition. Les reprises par prothèse ne posent absolument aucun problème avec ce type de comblement.The aim of this work was , on one hand, to evaluate the long term results of opening wedge high tibial osteotomy (HTO) and on the other to evaluate tolerance to and integration of Biosorb® wedges (Tricalcium Phosphate ß, SBM, Lourdes). Our series comprised 124 knees in 110 patients (74 men, 36 women), mean age 53.23+/-10.68 years (32-74), who were operated on between June 1995 and December 2000 with predominantly medial compartment knee osteoarthritis. The mean Lysholm and Tegner pre-operative functional score was 65.44 +/- 13.32 (27-80) and the mean pre-operative hip-knee-ankle (HKA) angle was 172.51+/-3.8 (162-179). Using the modified Alhbäck classification for knee osteoarthritis there were 27 stage I, 42 stage II, 44 stage III and 11 stage IV knees. All patients were reviewed clinically and radiographically with a mean follow-up of 10.39 +/- 1.98 years (8-14 years). In terms of immediate post-operative complications, there were 9 undisplaced lateral tibial plateau fractures which were asymptomatic, 2 deep vein thromboses and 3 pulmonary emboli which resolved with appropriate treatment and 3 cases of delayed wound healing. In terms of late complications there were 7 delayed unions but no non-unions. 3 screw breakages occurred when the AO T-plate was used, one of which resulted in a secondary loss of correction which necessitated revision by femoral osteotomy.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Une nouvelle procédure d'identification des paramètres de lois cohésives

International audienceL'objectif est ici d'introduire un nouvel outil de caractérisation de lois cohésives, modèle le plus couramment utilisé pour décrire et simuler le phénomène de délaminage. Cet outil est basé sur une méthode de corrélation d'image globale, où la définition de l'espace de recherche cinématique est adéquatement choisie. Après avoir présenté le principe de cette méthode, on s'intéresse à sa validation, ainsi qu'à son comportement au bruit. Cette validation est réalisée numériquement, (i) en construisant un ensemble d'images à l'aide d'un outil de simulation évolué du délaminage et (ii) en identifiant à partir de ces images les caractéristiques du comportement de l'interface

Integrated global digital image correlation for interface delamination characterization

Interfacial delamination is a key reliability challenge in composites and micro-electronic systems due to (high-density) integration of dissimilar materials. Predictive finite element models are used to minimize delamination failures during design, but require accurate interface models to capture (irreversible) crack initiation and propagation behavior observed in experiments. Therefore, an Integrated Global Digital Image Correlation (I-GDIC) strategy is developed for accurate determination of mechanical interface behavior from in-situ delamination experiments. Recently, a novel miniature delamination setup was presented that enables in-situ microscopic characterization of interface delamination while sensitively measuring global load-displacement curves for all mode mixities. Nevertheless, extraction of detailed mechanical interface behavior from measured images is challenging, because deformations are tiny and measurement noise large. Therefore, an advanced I-GDIC methodology is developed which correlates the image patterns by only deforming the images using kinematically-admissible ‘eigenmodes’ that correspond to the few parameters controlling the interface tractions in an analytic description of the crack tip deformation field, thereby greatly enhancing accuracy and robustness. This method is validated on virtual delamination experiments, simulated using a recently developed self-adaptive cohesive zone (CZ) finite element framework

On image gradients in digital image correlation

International audienceIn digital image correlation (DIC), the unknown displacement field is typically identified by minimizing the linearized form of the brightness conservation equation, while the minimization scheme also involves a linearization, yielding a two-step linearization with four implicit assumptions. These assumptions become apparent by minimizing the non-linear brightness conservation equation in a consistent mathematical setting, yielding a one-step linearization allowing a thorough study of the DIC tangent operator. Through this analysis, eight different image gradient operators are defined, and the impact of these alternative image gradients on the accuracy, efficiency, and initial guess robustness is discussed on the basis of a number of academic examples and representative test cases. The main conclusion is that for most cases, the image gradient most common in literature is recommended, except for cases with: (1) large rotations; (2) initial guess instabilities; and (3) costly iterations due to other reasons (e.g., integrated DIC), where a large deformation corrected mixed gradient is recommended instead

Interface debonding characterization by image correlation integrated with Double Cantilever Beam kinematics

A procedure is proposed for the identification of spatial interfacial traction profiles of peel loaded Double Cantilever Beam (DCB) samples, from which the corresponding traction-separation relation is extracted. The procedure draws upon recent developments in the area of non-contact optical techniques and makes use of so-called Integrated Digital Image Correlation (I-DIC) concepts. The distinctive feature of the I-DIC approach proposed herein is that the unknown degrees of freedom are not displacements or rotations, but the set of interfacial fracture properties describing the traction profile. A closed-form theoretical model is developed to reconstruct a mechanically admissible displacement field representing the deformation of the adhering layers during debonding in the DCB fracture test. The proposed modeling accounts for the spatial traction profile along the interface between the adherends using few degrees of freedom, i.e. crack tip position, maximum stress and size of the process zone. By minimizing the correlation residual with respect to the degrees of freedom, the full set of interfacial fracture properties is obtained through a one-step algorithm, revealing a substantial gain in terms of computational efficiency and robustness. It is shown that the identified traction profile can be effectively combined with the crack opening displacement to extract the corresponding traction-separation relation, i.e. the key input data for any cohesive zone model (CZM). The proposed procedure is validated by post-processing virtually deformed images generated through the finite element method. The robustness with respect to noisy data, as well as the low sensitivity to the initial guess, are demonstrated. © 2014 Elsevier Ltd. All rights reserved