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Mechanical behaviour of knit synthetic mesh used in hernia surgery

Tomaszewska A.

Acta of Bioengineering and Biomechanics

2016

Vol. 18, no. 1

77--86

Purpose: There is a discussion in literature concerning mechanical properties and modelling of surgical meshes. An important feature of elastic modulus dependency on load history is taken into account in this paper, as implants are subjected to variable loading during human activity. The example of DynaMesh®-IPOM surgical implant is studied. Methods: The analysis is based on failure tension tests and cyclic loading and unloading tests performed for the material samples. Stiffness changes of the material samples within successive load cycles are noted. The values the elastic modulus of the material tend to during successive cycles determine the material stiffness in the preconditioned state. The analysis is performed for two axes of the mesh, as the material reveals orthotropic properties. Results: For the initial displacements state of the material bilinear stiffness functions are determined for the two considered material axes. The functions for the preconditioned state are specified basing in the observed stiffness changes in subsequent loading cycles in experiments with different load (and strain) ranges. The identified elastic modulus values for different strain levels in the preconditioned state are then a basis for the nonlinear stiffness function formulation. Conclusions: The author concludes that two states of the considered mesh should be considered in calculations, initial and preconditioned ones. As the material stiffness in its preconditioned state is higher than in the initial one, omitting of the preconditioned state in calculation, e.g., considering fixation of the mesh, may lead to underestimation of necessary fixation strength.

Komputerowa symulacja membrany stosowanej w leczeniu przepuklin brzusznych

Szepietowska K.

Aktualne Problemy Biomechaniki

2011

z. 5

159--164

Z uwagi na częste nawroty choroby i chęć zminimalizowania bólu u pacjentów po operacjach przepukliny wykonanych metodą wideoskopową, lekarze poszukują optymalnej liczby zszywek łączących implant z tkanką ludzką. Celem pracy jest analiza wpływu warunków brzegowych na siłę ścinająca zszywki. Metodą Elementów Skończonych przeanalizowano dwa modele membran: z podporami sztywnymi i z podporami sprężystymi. Wywnioskowano, że przyjmowanie modelu z podporami sprężystymi jest bardziej wskazane, ponieważ model ten jest bezpieczniejszy i bardziej odpowiada rzeczywistości.

Due to frequent recurrences and desire to minimize pain after hernia repair operation, physicians are looking for the optimal number of joints which connect implant with human tissue. The main aim of this study is to analyze the influence of boundary conditions on the shear strength in joints. Two models of membrane have been analyzed using Finite Element Method: with stiff supports and with elastic supports. In conclusion, the solution with elastic supports seems to be more appropriate due to the boundary conditions closer to real tissue-implant system and also safer if considering the shear force value in the joints.