Equi-Biaxial Tests for Mechanical Characterization of Human Acellular Dermal Matrices Through a Custom-Made Biaxial Fixture

Abstract

Human Acellular Dermal Matrices (HADMs) have recently been employed in reconstructive surgeries which involve high mechanical resistance prerequisites (e.g. rotator cuff tears repair, Achilles tendon augmentation, breast reconstruction procedure, hernia repair), having proved its non-immunogenic response and promising mechanical properties. Nevertheless, a thorough mechanical characterization is needed in order to test HADMs response when subjected to stress levels comparable to those experienced in vivo, to confirm its applicability to the above mentioned surgical fields and to provide precise indications to surgeons. HADMs specimens have undergone biaxial tests through a custom made biaxial fixture interfaced with a uniaxial universal testing machine. Stress-strain curves were evaluated from biaxial loads measured by two load cells, and the optical measure of the displacement of four markers located in central area of specimens. Comparisons among the native human reticular dermis and HADMs demonstrated the loss of mechanical strength caused by the decellularization process. Moreover, the specimens resulted, on average, less extensible in the medio-lateral direction (namely, along the Langer lines) than in the cranio-caudal direction, confirming the correlation of dermis mechanical response with collagen fibers orientation.