Mechanical characterization of human superficial fascia: an experimental comparison between the abdominal and the thoracic district

Human abdominal superficial fascia, also known as Scarpa’s fascia, is a connective tissue whose mechanical properties, which are directly linked to its microstructure, have not yet been analyzed and literature lacks in information about its mechanical behavior. The purpose of this work was to investigate, by performing failure and stress-relaxation uniaxial tests, an eventual tissue anisotropy between orthogonal directions from tissue mechanical properties such as Young’s modulus and maximum strain/stress and viscoelastic mechanical properties. Results were compared with the ones obtained by testing a portion of thoracic superficial fascia of the back and then with the ones obtained by a previous work. Samples were harvested from two fresh-frozen cadavers: abdominal superficial fascia from both the left and the right side of the body came from an 85 years old male, while the thoracic portion of fascia from a 90 years old female (one side). Results obtained from failure tests showed that the tissue from both anatomical districts presented non-linear behavior and did not present a statistically significant anisotropy between directions, with the only exception of the stress in the two orthogonal direction of the right portion of abdominal SF. Mean values of 0.45 ± 0.11 mm/mm were obtained for the strain in the abdominal superficial fascia and of 0.44 ± 0.06 mm/mm for the thoracic superficial fascia of the back, mean values of 0.72 ± 0.36 MPa were obtained for the ultimate tensile stress in the abdominal fascia and of 2.49 ± 0.69 MPa for the thoracic fascia, 2.65 ± 1.51 MPa for Young’s modulus of the abdominal SF and 8.36 ± 1.87 MPa for the thoracic fascia of the back. The thoracic superficial fascia of the back presented higher stiffness than the abdominal SF. Stress relaxation tests proved the viscoelastic behavior of the superficial fascia of both districts and both districts presented increased stiffness resulting from an increase in strain rate. This study added new data for the description of mechanical properties of the tissue by performing uniaxial failure and stress-relaxation tests, these findings represent only the first step towards a complete characterization of abdominal SF mechanical behavior and towards the refinement of its application in sectors such as the personalization of treatment for physical therapy and reconstructive surgery. An enlarged sample size could further proof of the concept.