Mechanical behavior of human breast tissues: ex vivo and in silico characterization.

To study the mechanics of a biological tissue is crucial to understand its behavior under a variety of realistic loading conditions. In particular, an accurate estimation of the mechanical properties of breast tissues is essential to enhance current diagnostic techniques, such as mammography, and to improve clinical treatments, including tissue engineering approaches. This study focuses on the mechanical characterization of human breast tissues, harvested from women who underwent a mammary reduction surgery. Ex vivo experiments, consisted in indentation tests, were performed to determine the elastic properties. Additionally, using inverse finite element analysis, the hyperelastic properties were obtained for the Yeoh and Ogden (N = 3) constitutive models. The samples were grouped based on the characteristics of the female population (i.e., age, body mass index and menopausal status) and according to the breast side (tissue sample site). Significant differences in the Young's modulus were only observed in association with age and menopausal status, in the first linear region (3.75-11.5% strain) of the experimental curve. In the second linear region (22.5-30% strain), although samples presented a higher stiffness, no significant differences were observed. Regarding the hyperelastic properties, Yeoh and Ogden (N = 3) models accurately fit the experimental data, presenting errors lower than 3.26% and 3.86%, respectively. In this work, the model developed successfully converged with a 3 mm of indentation (corresponding to 30% of deformation), enabling reliable analysis in the large deformations domain. The findings of this study provide valuable insights that can contribute to future clinical applications and research, including improvements in diagnostic techniques, treatments and esthetic reconstructions.