Structural-mechanical characterization of human ligaments using a custom-made tensile test chamber combined with the Skyscan1176 system

Anterior cruciate ligament (ACL) injuries are one of the major and one of the most frequent clinical problems in orthopedics1. Connecting femur and tibia, the ACL decreases the joint degrees of freedom and maintaines joint stability under load conditions. Thus, ACL plays a fundamental role in the stability and functionality of the knee. When injured, the common approach lies on its surgical reconstruction by using several types of graft2. However, surgical or implant reconstruction techniques still show unsatisfactory long-term success. Therefore, the knowledge of the biomechanical, structural and morphological properties of native tissues is fundamental in order to reduce the need of surgical revision and the probability of early development of other pathologies, such as osteoarthritis. This better understanding of the properties of ACL could help to optimize the choice and the development of new grafts and scaffolds. Dense connective fibrous tissues, such as ACL, typically exhibit non-linear stress-strain characteristics related to fibers crimp, orientation and tension, which intrinsically define its functional properties. The behavior of ACL bundles in relation of its fibrous structure has already been studied under load, but considering only the outer surface and not the entire 3D structure3. Aim of this study was to design and test a dedicated setup able to acquire the volumetric fibrous microstructure of the ACL samples, under progressive increasing mechanical strain.