OC-122 CHARACTERISATION OF HUMAN POSTERIOR RECTUS SHEATH REVEALS MECHANICAL AND STRUCTURAL ANISOTROPY

Abstract

Abstract Background Our work investigated the mechanical properties of the posterior rectus sheath (PRS) in terms of its ultimate tensile stress (UTS), stiffness, thickness and anisotropy as well as assess the collagen fibre organisation of the PRS using Second-Harmonic Generation (SHG) microscopy. Methods For mechanical analysis, twenty-five fresh-frozen PRS samples of were taken from six different cadaveric donors. They underwent uniaxial tensile stress testing until rupture either in the transverse (n=15) or longitudinal (n=10) plane. The thickness of each sample was also recorded using digital callipers. On a separate occasion, ten PRS samples and three anterior rectus sheath samples underwent SHG microscopy and photography to assess collagen fibre organisation. Results PRS samples had a mean UTS of 7.7MPa (SD 4.9) in the transverse plane and 1.2 MPa (SD 0.8) in the longitudinal plane (P<0.01). The same samples had a mean Youngs modulus of 11.1 MPa (SD 5.0) in the transverse plane and 1.7 MPa (SD 1.3) in the longitudinal plane (P<0.01). The mean thickness of the posterior rectus sheath was 0.51mm (SD 0.13). Collagen fibres within the tissue could be identified with SHG microscopy, generally aligned transversely. Conclusion The PRS displayed mechanical and structural anisotropy with greater tensile stress and stiffness in the transverse plane compared to the longitudinal plane. The mean thickness of this layer is around 0.51mm – consistent with other studies. The tissue is constructed of transversely aligned collagen fibres that are visible using SHG microscopy.