Transvaginal Mesh Insertion in the Ovine Model

The overall goal of this experimental surgical procedure is to use a single vaginal incision to implant mesh into the recto vaginal septum, with or without trocar guided insertion of the anchoring arms. The sheep is a useful model as the ovine pelvic floor experiences similar changes to those that occur during human childbirth, and as the sheep dimensions permit comparable surgical interventions. The main advantage of this technique is that it uses a widely available non primate large animal model that makes a clinically implemented surgical approach to transvaginal implantation.

Though this method can provide insight into the surgical treatment of pelvic organ prolapse with implants it can also be applied to other surgical techniques, like native tissue repair. Visual demonstration of this method is critical, as it is difficult to teach these surgical techniques without being able to observe them. After confirming that the sheep is sleepy and lethargic, place the animal in the lithotomy position on the end of the surgical table and use ropes to secure the limbs with the hips in hyperflexion.

Next, push transvaginally on the bladder to empty the organ and manually empty the rectum, followed by shaving of the perineum, the medial area of the thigh, and the tail folds. Disinfect the exposed skin with 7.5%povidone iodium and after donning the appropriate personal protective equipment cover the animal with a sterile drape, with an opening above the genital hiatus. Use allis forceps to grasp the dorsal vaginal wall three centimeters cranial to the hymenal ring.

Then, use a 10 milliliter syringe loaded with a 22 gauge needle to inject saline three to four millimeters under the vaginal epithelium along the mid line of the recto vaginal septum 1.5 centimeters cranial to the hymenal ring. Aqua dissect the vaginal tissue by injecting the saline into the recto vaginal septum. Then use a scalpel to make a three centimeter long mid line incision on the vaginal epithelium starting caudal to the allis forceps and ending at the hymenal ring.

Hold the incision open with a self retaining retractor over the perineum and four sharp stay hooks. Then use your index to bluntly dissect the recto vaginal fascia from the vaginal wall laterally toward the pelvic side walls and cranially up to the caudal aspect of the cul-de-sac. At this point, you can insert either the rectangular implant or continue with dissection to insert the implant with anchoring arms.

When a suitable space has been created for the 30 by 40 millimeter flat mesh insert a vaginal retractor into the incision and use a simple interrupted three oh polypropylene suture on the left and right sides of the most cranial aspect of the dissected recto vaginal space to suture the left and right cranial corner of the implant. Trim the residual suture material and add one additional simple interrupted suture midway along the cranial aspect of the implant. Suture the lateral edges of the implant midway onto the surrounding connective tissue, with a simple interrupted three oh polypropylene suture.

Suture the left and right caudal corners with simple interrupted three oh polypropylene sutures on the left and right sides of the most caudal aspect of the recto vaginal space. Then add one additional simple interrupted suture midway along the caudal aspect of the implant, and close the vaginal incisions with a running three oh polyglactin suture, which will be shown at the end of the video. This is another operation.

Alternatively, one can continue the recto vaginal space cranial ventrally to reach the medial aspect of the obturator foramen and also dissect the space caudolaterally to reach the caudally located coccygeus muscle. With a number 24 blade, make four one centimeter wide incisions on the vulvar side cutting through the skin and superficial muscular fascia. Make two ventral incisions on the medial aspect of the thigh, approximately four centimeters cranial from the caudal border of the sciatic arch, and three centimeters lateral from the midline.

Make two dorsal incisions at the insertion of the tail folds two centimeters medial to the tuber ischiadicum. Then place a curved trocar through one of the ventral incisions. Controlling the progression of the trocar with a finger inserted through the vaginal incision, pass the trocar through the abductor magnus muscle, the external obturator, and the medial aspect of the obturator foramen.

Take special care when pushing the trocar, as pushing the trocar in the wrong direction may cause severe injury to the vessel or nerve both of which are located in the cranial aspect of the obturator foramen. Guide the tip of the trocar to the tendonous arc of the levator ani muscle, and expose the guiding wire in the vaginal wall incision. Load the wire with the corresponding ipsilateral cranial mesh arm and pull the loaded trocar through the tissues, keeping the mesh arm tension free.

Then load the guide wire with the second cranial arm through the ventral incision on the other side of the animal and pull the trocar through the tissues, as just demonstrated. Now pass the trocar through the coccygeus muscle via one of the dorsal incisions just distal to the sacrotuberous ligament, and expose the guide wire through the vaginal incision. Grasp the dorsal arm of the mesh and pull the mesh out, keeping the arm tension free.

Transfer the second arm of mesh to the other side of the animal as just demonstrated, and adjust the mesh position by flattening and applying tension to both arms, while keeping the mesh tension free. Using simple interrupted three oh polypropylene sutures in the middle of the caudal borders, secure the mesh to the surrounding connective tissue. Then cut the arms at the skin, and use simple interrupted three oh poliglecaprone sutures to close all of the skin incisions, followed by a running three oh poliglecaprone suture to close the vaginal incision.

In this experimental animal, the cranial arms were passed through the caudal aspect of the obturator foramen. The entry point of the trocar was at the tendonous arc of the levator ani two to 2.5 centimeters caudal to the obturator canal and the obturator vessels and nerve. The gracilis muscle was moved medially to display the course of the cranial arm through the semi tendinosis and the abductor magnus muscles.

The caudal arms were passed one centimeter to caudal to the caudal aspect of the broad sacrotuberous ligament, right through the coccygeus muscle. The central part of the mesh was placed flat with its cranial section stretching retroperitoneally under the caudal end of the cul-de-sac, and its caudal section down along the recto vaginal septum. Once mastered, this type of operation can be completed in 40 minutes.

Before attempting this procedure, it is important to remember to become familiar with the ovine pelvic anatomy and to obtain surgical skills, such as blunt and sharp dissection and hemostatic techniques. Following this procedure other methods like native tissue repair can be performed. After its development this technique paved the way for researchers in the field of urogynecology to explore implant augmented pelvis organ prolapse repair in an ovine model for vaginal surgery.

After watching this video you should have a good understanding of how to dissect the ovine recto vaginal septum to insert a flat rectangular implant and to use trocars to guide the insertion of an arm anchored implant. Don't forget that working with sharp objects, such as scalpels or needles may cause accidental injury or infection and that precautions such as paying full attention during the surgery should always be taken while performing this procedure.