Ex Vivo Uniaxial Tensile Properties of Rat Uterosacral Ligaments

Abstract

This manuscript presents new experimental methods for testing the ex vivo tensile properties of the uterosacral ligaments (USLs) in rats. The USL specimens ($n=21$) were carefully dissected to preserve their anatomical attachments, and they were loaded along their main in vivo loading direction (MD) using a custom-built uniaxial tensile testing device. During loading, strain maps in both the MD and the perpendicular direction (PD) were collected using the digital image correlation technique. The mean (± S.E.M.) maximum load and displacement at the maximum load were $0.98\pm 0.30$ N and $17.53\pm 3.87$ mm, respectively. The USLs were found to be highly heterogeneous structures, with some specimens experiencing strains in the MD that were lower than $5\%$ and others reaching strains that were up to $60\%$ in the intermediate region. At 0.5 kPa stress, a value reached by all the specimens, the mean strain in the MD was $9.15 \pm 1.30\%$ while at 5 kPa stress, a value achieved only by 9 out of the 21 specimens, the mean strain increased to $23.87 \pm 3.64\%$. Under uniaxial loading, the specimens also elongated in the PD, with strains that were one order of magnitude lower than the strains in the MD; at the 0.5 kPa stress, the mean strain in the PD was recorded to be $0.69 \pm 0.66\%$ and, at the 5 kPa stress, the strain in the PD was $6.99 \pm 2.87\%$. The directions of maximum principal strains remained almost unchanged with the increase in stress, indicating that little microstructural re-organization occurred due to uniaxial loading. This study serves as a springboard for future investigations on the supportive function of the USLs in the rat model by offering guidelines on testing methods that capture their complex mechanical behavior.