Anatomy and pathogenesis
At 10cm dilation of the cervix, both CL and USL may be stretched or torn because of pressure of the head as it enters the birth canal. In the menopause, further ligament weakness may occur because of collagen break down. CL prolapses down onto the lateral part of the cervix, fig3, and the bladder rotates down like a trapdoor as a cystocele (transverse defect), fig3.
The same 10cm cervical dilatation may overstretch the attachments of USL to weaken and elongate them, fig 2, and separate them laterally to form an enterocele.
It is evident from fig2, that the cardinal ligaments MUST elongate in parallel with uterosacral ligament elongation. Therefore both CL and USL must be repaired, and the fascial layer of vagina re-attached, fig3.