The Superficial Inferior Epigastric Artery Fascia Flap for Nerve Reconstruction in Rabbits

[Narrator] This video provides a step-by-step instruction on how to harvest a pedicled superficial inferior epigastric artery fascia, or C flap, to wrap it around the nerve in a rabbit peroneal nerve defect model, a validated method to revascularize nerve grafts and enhance nerve regeneration. The C flap is a pedicled flap supplied by superficial inferior epigastric vessels, including both the arteries and accompanying veins. The vessels arise from the femoral vessels in proximity of branches of the popliteal and saphenous vessels distal from the inguinal ligaments. The main trunk divides into the main lateral trunk, vascularizing the abdominal wall skin, and the smaller medial branch vascularizing the medial abdominal skin. Induce anesthesia by intermuscular administration of ketamine and xylazine. Intubate the rabbit and ventilate with isoflurane using a ventilation system. Monitor the vital parameters during surgery. Place the rabbit on its side and prepare it for sterile surgery. Ensure the leg can be maneuvered during the surgery. First, the surgical approach to the peroneal nerve. Create a 10-centimeter incision in the skin of the posterolateral side of the thigh parallel to the femur in order to expose the peroneal nerve branch of the sciatic nerve. Separate the biceps femoris muscle from the gluteus maximus and vestus lateralis muscle by dissecting the fascia plane between these muscles. Here you can appreciate the fascia plane that needs to be separated. Use a retractor to visualize and perform a blunt dissection to expose a nerve layer by layer. Ensure the fascia is released over the entire length of the nerve to create enough room for the flap. Reposition the retractor to maximize the access to the nerve when needed. Carefully separate the nerve from the surrounding connective tissue. Ligate and cut the caudal femoral artery and vein for better mobility of the nerve. If needed, place another retractor to maximize access to the nerve. Here you can appreciate the sciatic nerve and its branches. If necessary, place a microsurgery background sheath under the nerve for better visibility. Carefully isolate the common peroneal nerve branch of the sciatic nerve. This is usually the most ventral branch. If necessary, you can further isolate the branch under the surgical microscope. The nerve site is now prepared for reconstruction after raising of the adipofascial flap. Temporarily approximate the skin. Next, continue to the surgical approach to the adipofascial flap. Place the rabbit in a supine position. Starting under the xiphoid and medial to the nipple line, create a superficial 10 to 14-centimeter paramedian incision in the epidermis. Bluntly dissect the fascia from the skin, and release the incision step by step to avoid harming the fascia. Ligate small epidermal perforating branches as needed. Place single, 4-O nylon sutures in the epidermis along each side of the incision with mosquito forceps on each suture to delicately maneuver the skin while separating the skin from the subcutaneous tissues. Separate the skin from the fascia to ensure plenty of room to dissect a 14 by 10-centimeter flap in the ventral abdomen. Bipolar cauterize small epidermal perforating branches as needed. Take care to avoid damage to the pedicle while separating the skin from the fascia. If needed, further retract the skin to maximize visibility. Dissect the flap starting on the medial side, lateral from the linea alba in a cephalic direction. Elevate the fascia while dissecting to avoid harming the abdominal muscles. As you further dissect the flap, separate the superficial and deep membranous layers of subcutaneous tissue from the abdominal muscles, leaving the fascia intact. Next, continue to the transverse dissection. Further separate the skin from the fascia where needed to create more room for the dissection. Ligate the pedicle as cranial as possible and complete the transverse dissection. As you continue, further separate the superficial and deep membranous layers of subcutaneous tissues between the abdominal muscles and the fascia, leaving the fascia intact. Next, continue to the lateral dissection in cephalic direction to completely elevate the flap. After dissecting the flap, raise the flap towards the level of the bifurcation of the femoral artery in both planes, taking care not to damage the pedicle. Further separate the superficial and deep membranous layers of subcutaneous tissue between the abdominal muscles and the fascia in order to completely raise the flap for tunneling. Next, we continue to creating a tunnel for the flap. Bluntly dissect a wide subcutaneous tunnel into the inguinal region above the fascia layer. Widen the tunnel from both sides to ensure that the flap will not be constricted. Here you can appreciate the full length of the elevated flap before tunneling it towards the nerve reconstruction site. Pass the flap through the tunnel, such that the flap is rotated approximately 100 degrees clockwise about its axis, and the vessels are kept ventrally. Ensure that there is no pedicle torsion or compression in the subcutaneous tunnel. The flap is now rotated towards the nerve reconstruction site through the subcutaneous tunnel and is ready for reconstruction. After approximating the abdominal incision in layers, the nerve reconstruction site will be prepared for repositioning of the flap. Here you can appreciate the length and width of the flap as well as the bleeding of the pedicle. Re-expose the peroneal nerve reconstruction site using a retractor. Reposition the flap around the retractor. Ensure that there is no compression of the flap. Elevate the nerve with a vessel loop to reposition the flap under the nerve. Ensure that there is enough length of the flap to cover both anastomoses without compressing the nerve or the pedicle with full mobility of the leg. Next, the nerve reconstruction. First, reposition the microsurgery background sheath. Further separate the peroneal nerve branch under the surgical microscope if necessary. Six centimeters distal to the border of the external obturator muscle, excise a 25-millimeter segment of the peroneal nerve by sharp transection. Reconstruct a defect with a 30-millimeter nerve graft using 10-O nylon epineural sutures on either side of the anastomosis. Loosely wrap the C flap around the nerve with the pedicle vessels in line with the nerve covering the proximal and distal anastomoses without tension on the nerve. Trim the edges as needed. Loosely place two 4-O absorbable sutures through the edges of the flap to secure it around the anastomoses. Approximate the hind limb incision in layers. Subcutaneously administer norfloxacin, carprofen, and buprenorphine prior to recovery, and once daily for five days postoperatively. The C flap is a durable flap resulting in a total success rate of flap viability. Flap viability can be tested during sacrifice using the test of the pedicle, assessing the color of the flap, and assessing the bleeding at the edges of the flap. Postoperative flap-related complications should be monitored. Immunohistochemistry can be used to measure the presence of fibrosis and neovascularization. Micro CT scanning can be used to measure neovascularization patterns. After watching this video, you should have a good understanding on how to replicate the surgical approach for vascularizing nerve grafts using the C flap in the rabbit peroneal nerve defect model.