INTEREST OF FINITE ELEMENT ANALYSIS TO DETERMINE STRESS FIELDS AT THE SUMMIT OF A VY FLAP ABOUT ONE CLINICAL CASE

International audienceAfter performing a V-Y advancement flap, we observed an unusually shaped necrosis, resembling a keyhole at the apex of the flap. As high closing tensions are an accepted cause of skin necrosis, we developed a mathematical model based on the finite element analysis in order to determine the stress field by simulating the mechanical behavior of human skin during suture and to explain this particular shape of necrosis. For the modeling, a planar nonlinear two-dimensional finite element model was used. The numerical simulation was carried out with Ansys® v12 software. Results are expressed in numerical and graphic form. The shape of the vertical iso-stress line for a stress equal to 18.8 kPa was similar to the necrosis observed in our clinical case. Similarities between the shape of necrosis and the calculated stress field at the apex of the V-Y advancement flap indicate the major role of skin tension in this necrosis. Finite element analysis is an original approach for describing the particular shape of a necrosis. Although many factors can be implicated in skin necrosis, the modeling confirms the role of tension in the necrosis of this particular case

Influence of the V-Y advancement flap geometry on the wound closure maximal force

International audienceIn clinical practice, the V-Y advancement flap is a widely used technique to cover human skin defect, which consists in incising; advancing and suturing a triangular flap adjacent to the base of a rectangular defect (see Figure 1a). A previous geometrical study of the V-Y flap technique allowed us to find a good compromise between the flap size and the defect width [1]. However, the geometrical approach does not consider the mechanical properties of the human skin by assuming rigid-body behaviour of the skin. The aim of the present paper deals with a numerical analysis as a complement to the geometrical one to highlight the major role of the skin elasticity in the V-Y advancement flap. A compromise between the size of the flap and the level of the closure force value has been found when varying the angle at the flap apex, noted . The sensitivity to the mechanical parameters makes the closure force dependent on the size to be covered. At the end, the successive actions of the surgeon are analyzed

Efficacy of trabectedin in metastatic solitary fibrous tumor

Solitary fibrous tumor is a rare tumor type and has an unpredictable course. Local recurrence rate varies between 9 and 19%, and rate of metastatic involvement between 0 and 36 %. It is characterized by a typical architecture and immuno-histochemistry tests. The most important prognostic factor is the complete resection of primary tumor. Treatment of recurrences is not clearly established. If a solitary fibrous tumor is too advanced to allow surgical resection, radiotherapy and chemotherapy may be used. The most often used drugs are doxorubicine and\or ifosfamide. We report the case of man with metastatic solitary fibrous tumor treated with trabectedin, administered at a dose of 1.5 mg/m² every 3 weeks. After 3 cycles, metastases had significantly decreased. Recurrence of the disease was demonstrated 8 months after the start of trabectedin. This case shows that trabectedin is a possible treatment option

La reconstruction mammaire par prothèse (à propos de 32 patientes revues au CHU de Besançon)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

Séquelles fonctionnelles des lambeaux aux dépens du muscle triceps sural (évaluation clinique et baropodométrique)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

Les seins tubéreux (à propos de 51 patientes revues)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

Couverture par lambeau libre des fractures ouvertes de jambe (rôle du délai de couverture)

BESANCON-BU Médecine pharmacie (250562102) / SudocSudocFranceF

Numerical analysis of the V-Y shaped advancement flap

International audienceThe V-Y advancement flap is a usual technique for the closure of skin defects. A triangular flap is incised adjacent to a skin defect of rectangular shape. As the flap is advanced to close the initial defect, two smaller defects in the shape of a parallelogram are formed with respect to a reflection symmetry. The height of the defects depends on the apex angle of the flap and the closure efforts are related to the defects height. Andrades et al. 2005 have performed a geometrical analysis of the V-Y flap technique in order to reach a compromise between the flap size and the defects width. However, the geometrical approach does not consider the mechanical properties of the skin. The present analysis based on the finite element method is proposed as a complement to the geometrical one. This analysis aims to highlight the major role of the skin elasticity for a full analysis of the V-Y advancement flap. Furthermore, the study of this technique shows that closing at the flap apex seems mechanically the most interesting step. Thus different strategies of defect closure at the flap apex stemming from surgeon’s know-how have been tested by numerical simulations

Intra-and inter-individual variability in the mechanical properties of the human skin from in vivo measurements on 20 volunteers

International audienceBackground/Purpose : The mechanical properties and behavior of the human skin in vivo are of medical importance, particularly to surgeons who have to consider the skin extension capabilities in the preparation of surgical acts. Variable data can be found in literature that result from diverse kinds of tests (in vivo, ex vivo, post-mortem) performed with different instruments.Methods : This paper presents the results of in vivo measurements performed on a cohort of 20 healthy volunteers with an ultralight homemade uniaxial extensometer. Different anatomical zones were explored under different directions of solicitation in order to document inter- and intra-individual variability as well as skin anisotropy.Results : The experimental data obtained are fitted with a phenomenological exponential model allowing the identification of three parameters characteristic of the tested skin behavior. These parameters can be related to the concept of skin extensibility used by surgeons.Conclusion : The inter- and intra-variability observed on that cohort confirms the need for a patient-specific approach based on the in vivo measurement of the mechanical behavior of the human skin of interest. Even the direction of higher skin stiffness is found to be individual dependent. The capability of the extensometer used in this study to fulfill such measurement needs is also demonstrated

Analyses expérimentale et numérique d'un lambeau d'avancement V-Y réalisé sur la peau humaine ex vivo

Le but de ce travail est d'optimiser la géométrie du lambeau V-Y, technique chirurgicale permettant, par la mobilisation d'un lambeau en V, la couverture de certaines pertes de substance. A partir d'un explant d'abdominoplastie, un lambeau V-Y a été réalisé pour évaluer expérimentalement et prédire numériquement les efforts de fermeture. Une modélisation 2D par éléments finis est proposée en considérant la peau comme un matériau homogène avec un comportement mécanique isotrope hyperélastique quasi-incompressible