Mechanical and microstructural characterization of the human tunica albuginea

The tunica albuginea (TA) is a fibrous connective membrane surrounding the corpora cavernosa (CC), which plays a crucial role in the erection. In case of erectile dysfunction, inflatable penile prothesis (IPP) may be a treatment of choice and mechanical interactions occur between prostheses and these penile tissues. There is still much to be learned about their mechanical behavior to help to improve IPP and penile surgical techniques. This paper presents the characterization of the TA mechanical behavior combined with the observation of its microstructural organization, as well as the mechanical behavior of the cavernous tissue. Uniaxial tensile tests were performed on 40 TA samples and 17 CC samples collected from 5 post mortem human subjects. TA samples were cut along both longitudinal and circumferential directions, and in both proximal and distal regions. Histological slices were produced from biopsies contiguous to the samples to observe the collagen fiber organization in the TA. We observed that this fiber organization usually schematized by 2 layers of perpendicular fibers is more complex, with some dispersion in the fiber orientations and interlacing of the 2 layers. The mechanical characterization of the TA samples revealed no clear anisotropy but different properties for the proximal and distal locations, whereas the CC showed a very low elastic modulus. These data complement those already published and further analysis of the microstructure of the TA will be needed to explain the variability of the mechanical behavior of the TA in view of selecting and identifying nonlinear behavior models.