Experimental investigation of pressure applied on the lower leg by elastic compression bandage

International audienceCompression therapy with stockings or bandage is the most common treatment for venous or lymphatic disorders. The objective of this study was to investigate the influence of bandage mechanical properties, application technique and subject morphology on the interface pressure, which is the key of this treatment. Bandage stretch and interface pressure measurements (between the bandage and theleg) were performed on 30 healthy subjects (15 men and 15 women) at two different heights on the lower leg and in two positions (supine and standing). Two bandages were applied with two application techniques by a single operator. The statistical analysis of the results revealed: no significant difference in pressure between men and women, except for the pressure variation between supine and standing position; a very strong correlation between pressure and bandage mechanical properties (p<0.00001) and between pressure and bandage overlapping (p<0.00001); a significant pressure increase from supine to standing positions (p<0.0001). Also, it showed that pressure tended to decrease when leg circumference increased. Overall, pressure applied by elastic compression bandages varies with subject morphology, bandage mechanical properties and application technique. A better knowledge of the impact of these parameters on the applied pressure may lead to a more effective treatment

Characterization of Fabric-to-Fabric Friction: Application to Medical Compression Bandages

Fabric-to-fabric friction is involved in the action mechanism of medical compression devices such as compression bandages or lumbar belts. To better understand the action of such devices, it is essential to characterize, in their use conditions (mainly pressure and stretch), the frictional properties of the fabrics they are composed of. A characterization method of fabric-to-fabric friction was developed. This method was based on the customization of the fourth instrument of the Kawabata Evaluation System, initially designed for fabric roughness and friction characterization. A friction contactor was developed so that the stretch of the fabric and the applied load can vary to replicate the use conditions. This methodology was implemented to measure the friction coefficient of several medical compression bandages. In the ranges of pressure and bandage stretch investigated in the study, bandage-to-bandage friction coefficient showed very little variation. This simple and reliable method, which was tested for commercially available medical compression bandages, could be used for other medical compression fabrics

Étude biomécanique de l’action des bandes de compression sur le membre inférieur

Compression bandages are commonly used for the treatment of chronic venous insufficiency. They apply a pressure onto the leg, called interface pressure, which is one of the key aspects of the treatment. The objective was to better understand the mechanisms impacting interface pressure applied by compression bandage on the lower leg. In collaboration with clinicians and a medical devices manufacturer, a biomechanical approach was proposed. This approach was composed of experimental pressure measurements and the numerical simulation of bandage application. Two preliminary studies, experimental and numerical, showed the limitations of the use of Laplace’s Law (current standard) for interface pressure computation. These studies also questioned the possible impact of bandage surface properties (bandage-to-bandage friction coefficient) on interface pressure. They also showed the need to consider soft tissues deformation induced by bandage application. Two characterization methods were designed for the identification of patient-specific soft tissue mechanical properties and the measurement of bandage-to-bandage friction coefficient. A new methodology for the prediction of interface pressure was developed thanks to the combination of the numerical simulation of bandage application and the leg geometry parametrization. The results were then confronted to experimental measurements. Finally, a clinical study was designed to investigate the pressure applied by superimposed compression bandages (very common in clinical practice for the treatment of venous ulcers).Les bandes de compression, couramment utilisées pour le traitement de l’insuffisance veineuse, appliquent une pression sur la jambe, appelée pression d’interface, qui est le principe actif du traitement. L'objectif était de mieux comprendre les mécanismes influençant la pression exercée par une bande de compression sur le membre inférieur.En lien avec des médecins et un industriel, l’approche biomécanique proposée était composée d’une part expérimentale (mesures de pression d'interface) et d'une part numérique (modélisation éléments-finis de la pose d'une bande). Deux études préliminaires, expérimentale et numérique, ont montré la limite de l'utilisation de la Loi de Laplace (standard actuel) pour le calcul des pressions d’interface. Ces études ont soulevé des interrogations concernant l'éventuel impact des propriétés de surface des bandes (coefficient de frottement bande-bande) sur la pression. Elles ont aussi montré l’importance des déformations des tissus mous de la jambe induite par l'application de la bande. Deux méthodes de caractérisation mécanique ont donc été mises en place pour l’identification personnalisée des propriétés mécaniques des tissus mous de la jambe et la mesure du coefficient de frottement bande-bande.Un nouvel outil de prédiction des pressions d’interface a été développé grâce à la combinaison de la simulation numérique de la pose d’une bande et de la paramétrisation géométrique de la jambe puis il a été confronté aux mesures expérimentales.Finalement, une étude clinique a été réalisée pour étudier la pression exercée par la superposition de deux bandes de compression (pratique clinique très courante pour le traitement de l'ulcère veineux)

Biomechanical study of the action of compression bandages on the lower leg

Les bandes de compression, couramment utilisées pour le traitement de l’insuffisance veineuse, appliquent une pression sur la jambe, appelée pression d’interface, qui est le principe actif du traitement. L'objectif était de mieux comprendre les mécanismes influençant la pression exercée par une bande de compression sur le membre inférieur.En lien avec des médecins et un industriel, l’approche biomécanique proposée était composée d’une part expérimentale (mesures de pression d'interface) et d'une part numérique (modélisation éléments-finis de la pose d'une bande). Deux études préliminaires, expérimentale et numérique, ont montré la limite de l'utilisation de la Loi de Laplace (standard actuel) pour le calcul des pressions d’interface. Ces études ont soulevé des interrogations concernant l'éventuel impact des propriétés de surface des bandes (coefficient de frottement bande-bande) sur la pression. Elles ont aussi montré l’importance des déformations des tissus mous de la jambe induite par l'application de la bande. Deux méthodes de caractérisation mécanique ont donc été mises en place pour l’identification personnalisée des propriétés mécaniques des tissus mous de la jambe et la mesure du coefficient de frottement bande-bande.Un nouvel outil de prédiction des pressions d’interface a été développé grâce à la combinaison de la simulation numérique de la pose d’une bande et de la paramétrisation géométrique de la jambe puis il a été confronté aux mesures expérimentales.Finalement, une étude clinique a été réalisée pour étudier la pression exercée par la superposition de deux bandes de compression (pratique clinique très courante pour le traitement de l'ulcère veineux).Compression bandages are commonly used for the treatment of chronic venous insufficiency. They apply a pressure onto the leg, called interface pressure, which is one of the key aspects of the treatment. The objective was to better understand the mechanisms impacting interface pressure applied by compression bandage on the lower leg. In collaboration with clinicians and a medical devices manufacturer, a biomechanical approach was proposed. This approach was composed of experimental pressure measurements and the numerical simulation of bandage application. Two preliminary studies, experimental and numerical, showed the limitations of the use of Laplace’s Law (current standard) for interface pressure computation. These studies also questioned the possible impact of bandage surface properties (bandage-to-bandage friction coefficient) on interface pressure. They also showed the need to consider soft tissues deformation induced by bandage application. Two characterization methods were designed for the identification of patient-specific soft tissue mechanical properties and the measurement of bandage-to-bandage friction coefficient. A new methodology for the prediction of interface pressure was developed thanks to the combination of the numerical simulation of bandage application and the leg geometry parametrization. The results were then confronted to experimental measurements. Finally, a clinical study was designed to investigate the pressure applied by superimposed compression bandages (very common in clinical practice for the treatment of venous ulcers)

Combined experimental and numerical approach for the assessment of pressure generated by elastic compression bandage

International audienceElastic compression bandage is a common treatment for venous or lymphatic disorders. Even though the efficacy of this treatment is admitted, its mechanism remains poorly understood. The success of the treatment depends on the applied pressure, which depends on the bandage tension and the curvature of the limb (Laplace’s Law), the number of layers of the bandage, its components (padding layer, crepe …) and elastic properties, and the interactions between bandages and leg. To better understand the action of compression bandage, many interface pressure measurements have been done, but those measurements only give local information and for now, the whole pressure distribution on the leg is not known. Also, due to complex leg curvature and to bandage-leg and bandage-bandage interactions, the Laplace’s law is not sufficient to give a fine description of the pressure fields. Some simulations of the leg compression exist. Most of them are modeling the action of a compression sock on a leg [1][2], whose mechanical properties are more or less complex [3]. As far as we know, the simulation of bandage application on the leg has never been done yet. The aim of this communication is to present a first numerical model of the action mechanisms of bandages onto the skin developed through an experimental-numerical approach. A subject-specific FE model of bandage application is developed and compared with experimental measurements on two subjects

Numerical Model Reduction for the Prediction of Interface Pressure Applied by Compression Bandages on the Lower Leg

International audienceObjective: To develop a new method for the prediction of interface pressure applied by medical compression bandages. Methods: A finite element simulation of bandage application was designed, based on patient-specific leg geometries. For personalized interface pressure prediction, a model reduction approach was proposed, which included the parametrization of the leg geometry. Pressure values computed with this reduced model were then confronted to experimental pressure values. Results: The most influencing parameters were found to be the bandage tension, the skin-to-bandage friction coefficient and the leg morphology. Thanks to the model reduction approach, it was possible to compute interface pressure as a linear combination of these parameters. The pressures computed with this reduced model were in agreement with experimental pressure values measured on 66 patients' legs. Conclusion: This methodology helps to predict patient-specific interface pressure applied by compression bandages within a few minutes whereas it would take a few days for the numerical simulation. The results of this method show less bias than Laplace's Law, which is for now the only other method for interface pressure computation

Approche expérimentale et numérique pour l'étude de la pression d'interface appliquée par des bandages de compression

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SIMULATION/MODELISATION OF THE ACTION OF COMPRESSION BANDAGES ON THE LOWER LEG

International audienceCompression bandages are commonly used in the treatment of some venous or lymphatic pathologies. The success of the treatment relies on the applied pressure, which depends on several parameters related to the bandage but also to patients’ morphology. A previous experimental study showed that patient’s morphology and bandage elastic properties were not sufficient to explain interface pressure distribution [1]. However, these two parameters are the only one taken into account in Laplace’s Law, actual reference method to explain interface pressure distribution

BIOMECHANICAL STUDY OF PRESSURE APPLIED ON THE LOWER LEG BY ELASTIC COMPRESSION BANDAGES

International audienceCompression bandages are a common treatment for some lymphatics or venous pathologies. The treatment success directly depends on the pressure which is applied on the external surface of the leg and which is then transmitted to the internal tissues. This interface pressure (between the limb and the bandage) depends mainly on the following parameters:- the bandage components (padding layers, …)- their mechanical properties- the bandage stretch- the application technique (spiral, …) and number of layers (overlap)- patient’s leg morphology- other parameters such as friction between the different bandage layers.Though the efficacy of this treatment is admitted [1], its action mechanism and the pressure it applies on the leg remain poorly understood [2].For now, the reference method for the computation of interface pressure applied by compression bandage is Laplace’s Law:P = n T / r (1)with P the local pressure, n the number of layers of the bandage, T the bandage tension (i.e. force to stretch the bandage), r the local radius of curvature of the limb. However, this law, which only considers the non-deformed state of the limb, is unable to accurately predict interface pressures [3].The aim of this communication is to present a combined experimental and numerical approach for the assessment of interface pressure applied by compression bandages

Modelisation of the action of compression bandages on the lower limb

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