Biomechanical properties of tendons and the relationship with their microstructure

The mechanical characterization of soft biological tissues presents several technical difficulties. One of the most important is related to the change in mechanical behavior due to its origin (specific tissue of a particular individual), which poses a significant challenge in developing constitutive models due to the lack of adequate experimental information. For instance, although many material models have been proposed, most of them do not consider individual aspects of the tissue, which could provide an accurate mechanical prediction for a specific tissue of a particular individual. Aiming to identify individual parameters that could be correlated with mechanical behavior, an experimental study with tendons was carried out employing analysis at different levels of its structures. For the macroscopic level, lyophilization was used to obtain the percentage of dry weight. The diameter of the fibrils was obtained using scanning electron microscopy for the nanostructural level. Differential scanning calorimetry (DSC) was used to access parameters at the molecular-level. The correlation was evaluated regardless of the tendon origin, i.e., from different individuals or different positions of the same individual. Strong and statistically significant correlations were found between mechanical parameters and the individual parameters at the molecular-level. The study found a strong correlation between the peak temperature, measured using DSC, and the nominal tangent modulus. The correlation coefficient (r) was 0.803 with a p-value of less than 0.001. This discovery provides valuable insight into the connection between the structure of tendons and their macroscopic mechanical response. It is suggested that future studies can use the peak temperature parameter to establish correlations between tendons.