Cardinal and deep uterosacral ligament lines of action: MRI based 3D technique development and preliminary findings in normal women

The cardinal ligament (CL) and deep uterosacral ligament (US) play a critical role in utero-vaginal support. This study aims to quantify their geometrical relationships in living women using a MRI-based 3D technique. The angles between ligaments, the ligaments length and curvature were assessed on 3D models constructed from twenty MRIs of volunteers with normal support. How angle variation theoretically affects ligament tension was investigated using a simplified biomechanical model. The CLs are 18.1 A degrees A +/- 6.8 A degrees(SD) from the cephalic-caudal body axis , and the USs are dorsally directed and 92.5 A degrees A +/- 13.5 from the body axis. The CLs are longer and more curved than US. The theoretical calculated tension on CL is 52 % larger than that on US. The CL is relatively parallel to the body axis while the US is dorsally directed. The tensions on these ligaments are affected by their orientations.