Experimental and numerical assessment of the mechanics of keloid-skin composites undergoing large deformations

International audienceThe aim of this paper is to evaluate the stress fields in cutaneous tissues with the long-term goal to prevent keloid development in patients. Keloids are non cancerous tumors that expand continously on the skin for a number of reasons. These specific tumors affect 11 million more patients of all age, every year and are particularly frequent in the asian and african populations. The evolution of keloids is related to genetic, biological, biophysical and biomechanical factors and are considered \complex biological systems". Keloids develop due to the excessive proliferation of fibroblasts on several specific anatomical sites on the skin, that can be identified from the value of the retractability of the tissue. Keloids grow like expansive scars on the skin surface. The relation between their development and the mechanical stress fields in and around the Keloid were studied in some papers but to our knowledge one of the few attempts at formulating a growth criterion is due to who studied the influence of the local state of stress on the keloid propagation direction. The paper presents a patient-specific methodology to identify the stress field. A keloid was observed on a patient using several imaging modalities, namely ultrasound and optical microscopy. A 3D image of the surface of the keloid was used to develop a 3D geometrical model of the keloid under consideration. The hyperelastic properties of the keloid and of the healthy skin were obtained through independent testing, on the same patient using an custom-made extensometer. A three-dimensional numerical model of the keloid-skin composite was built in order to investigate the nature of the stress field in the vicinity of the keloid-skin interface. The validity of the simulation is determined by complementary data that have been recorded during the mechanical tests.The mechanical results obtained from the numerical model are compared to displacement fields identified by Digital Image Correlation