Emmanuelle Jacquet

A new experimental method for measuring skin's natural tension

Purpose: The precise determination of skins mechanical properties is still an open question. When performing an in vivo test, the piece of skin tested is not as well defined as it is in material testing. Moreover, the body zone and the body posture imply an initial stress on the skin. Consequently, a precise mechanical analysis needs a precise measurement of the natural skin tension.

Nonlinear model of skin mechanical behaviour analysis with finite element method.

Background/aims: A problem commonly encountered in plastic and reconstructive surgery is the prediction of the stress put on the skin when various types of skin flaps are used.

Development and characterization of a human dermal equivalent with physiological mechanical properties.

Different models of reconstructed skin are available, either to provide skin wound healing when this process is deficient, or to be used as an in vitro model. Nevertheless, few studies have focused on the mechanical properties of skin equivalent. Indeed, human skin is naturally under tension. Taking into account these features, the purpose of this work was to obtain a cellularized dermal equivalent (CDE), composed of collagen and dermal fibroblasts.

Geometrical analysis of the V–Y advancement flap applied to a keystone flap

BACKGROUND The V-Y advancement flap and, more recently, the keystone flap are commonly used to cover skin defects. Both flaps allow for primary closure after advancement by substituting the initial defect for a narrower defect distributed over a greater length. The first objective of this study was to develop a geometrical analysis of the V-Y advancement flap. The second objective was to explain the benefit of using the keystone flap compared to a single V-Y advancement flap. MATERIAL AND METHOD A geometrical analysis is proposed using a two-dimensional analysis in which the flaps are assumed to have a rigid-body behaviour. First, in the case of the V-Y advancement flap, a trigonometric relationship is defined between the distance of closure before and after advancement, thus implying the value of the flaps apex angle. Second, by considering the keystone flap as the association of three V-Y advancement flaps, the trigonometric relationship is applied to the keystone flap. RESULTS In the case of the V-Y advancement flap, the optimal apex angles are between 20° and 60°. At less than 20°, the length of the flap increases in an exaggerated manner. At greater than 60°, the distance of closure, particularly at the apex of the flap where a corner stitch is performed, is greater than the distance of closure of the initial defect. In the case of the keystone flap, the width of the final defect around the flap is clearly smaller and more regular compared to the final defect around a single V-Y advancement flap. CONCLUSION The geometrical analysis of the V-Y advancement flap in our description illustrates the major benefit of the keystone flap over a single V-Y advancement flap.

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

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, and postmortem) performed with different instruments.

Experimental and numerical analysis of a V-Y advancement flap on human skin ex vivo

D. Remache*, J. Pauchot, J. Chambert, L. Capek and E. Jacquet Department of Applied Mechanics, University of Franche-Comte, Femto-st Institute – UMR 6174 CNRS, 24 rue de l’ Epitaphe, 25000 Besançon, France; Orthopaedic, Traumatology, Plastic Reconstructive and Hand Surgery Unit, EA 4268I4S IFR133 INSERM, University Hospital of Besançon, Place Saint-Jacques, F-25030 Besançon, France; Department of Mechanical Engineering, Technical University of Liberec, Studenska 2, 46117 Liberec 1, Czech Republic

A human skin culture system for a wound-healing model.

The human body is very vulnerable and has to deal with open wounds due to injuries or diseases. A human skin culture model could help us to investigate wound-healing processes in an effort to find ...

Numerical analysis of keloid scar in the presternal area

Keloid scars are benign skin tumours that affect only humanity, especially among the Asian and African populations. Keloids consist in the excessive accumulation of dermal collagen that extends beyond the boundaries of the original wound (Kelly 2009). They are located on specific sites, tend to enlarge over time and pose aesthetic and psychological problems for patients. The physiopathology of keloids is unclear, and there is still no therapeutic consensus. Nevertheless, it appears that keloids result from a combination of genetic, cellular and mechanical factors (Salles et al. 2009). The purpose of this study is to predict the likely directions of extension of a presternal keloid as a function of mechanical stress field. Abdel-Fattah (1976) has assumed that a presternal keloid of initially oblong shape evolves into a claw-like pattern (or butterfly shape) over time. Based on geometrical and mechanical data from the literature, a finite element simulation of the skin in vivo in the vicinity of a presternal keloid of oblong shape is performed with Ansys software by assuming a linear elastic behaviour. The numerical results are then post-processed by Matlab software to predict the likely directions of extension of the keloid. Finally, the numerical predictions are compared with experimental results of Abdel-Fattah (1976). In particular, the growth direction of the keloid obtained from the clinical case is compared with the one computed by the maximum shear stress in the neighbourhood of the keloid.