The endopelvic fascia is a sheet of fibroareolar tissue following the blood supply to the visceral organs and acts as a retroperitoneal mesentery. The fascia divides the retroperitoneal space into avascular planes. The endopelvic or pubocervical fascia attaches the cervix and vagina to the lateral pelvic sidewall. It is composed of two parts: the parametrium, which is that part connected to the uterus (i.e., the uterosacral and cardinal ligaments), and the paracolpium, which is that part connected to the vagina. The parametrium and cardinal ligaments continue to the vaginal introitus and fuse directly to the supporting tissues associated with the vagina. The uterine and vaginal arteries travel in these structures. The uterosacral ligaments are the posterior components of the cardinal ligaments, extending from the cervix and upper vagina to the lateral sacrum. Lateral pelvic support is provided by linear condensations of obturator and levator ani fascia termed the arcus tendineus fascia pelvis and the arcus tendineus levator ani, respectively. The arcus tendineus levator ani serves as a point of attachment for the pubococcygeus and iliococcygeus muscles and lies on the fascia of the obturator internus muscle. It runs from the posterolateral pubic ramus to the ischial spine. The arcus tendineus fascia pelvis runs from the anterior pubis to the ischial spine as it joins with the arcus tendineus levator ani. It provides lateral (paravaginal) support to the anterior vagina.
Obturator Space The obturator membrane is a fibrous sheath that spans the obturator foramen through which the obturator neurovascular bundle penetrates via the obturator canal. The obturator internus muscle lies on the superior (intrapelvic) side of the obturator membrane. The origin of the obturator internus is on the inferior margin of the superior pubic ramus and the pelvic surface of the obturator membrane. Its tendon passes through the lesser sciatic foramen to insert onto the greater trochanter of the femur to laterally rotate the thigh. The obturator artery and vein originate as branches of the internal iliac vessels. As they emerge from the cranial side of the obturator membrane via the obturator canal and enter the obturator space, they divide into many small branches, supplying blood to the muscles of the adductor compartment of the thigh. Cadaver work contradicted previous reports that the obturator vessels bifurcate into medial and lateral branches (48). Rather, the vessels are predominantly small (<5 mm in diameter) and splinter into variable courses. The muscles of the medial thigh and adductor compartment are (from superficial to deep) the gracilis, adductor longus, adductor brevis, adductor magnus, obturator externus, and obturator internus. In contrast to the vessels, the obturator nerve emerges from the obturator membrane and bifurcates into anterior and posterior divisions, traveling distally down the thigh to supply the muscles of the adductor compartment. With the patient in the dorsal lithotomy position, the nerves and vessels follow the thigh and course laterally away from the ischiopubic ramus. Transobturator incontinence slings and anterior trocar-based mesh prolapse kits are often placed beneath the adductor longus tendon and just lateral to the descending ischiopubic ramus in order to avoid the obturator neurovascular bundle, which lies lateral and superior to this relatively safe point of entry through the obturator membrane.