Retrograde gastrocnemius nerve draining vascular flap for repair of heel skin defects
I. Anatomy of application
The gastrocnemius nerve is a cutaneous nerve, and its trophic vessels provide blood supply to the surrounding skin in addition to the nerve itself. The proximal end starts from the peroneal artery. To the distal end, it forms a rich anastomosis with the penetrating branches of the peroneal and posterior tibial arteries. This provides an anatomical basis for the use of retrograde flaps.
Flap design
1.Line: the line from the midpoint between the outer ankle and Achilles tendon to the midpoint of the carpal fossa as the axis (i.e., the course of the peroneal nerve).
2. Point: 5-7 cm above the ankle is the axial point. This is mostly for the nutrient vessels of the gastrocnemius nerve in the ankle and the peroneal artery through the branch to form through the branch anastomosis
Therefore, the axial point should be changed to the site with blood flow and the axis should be modified to the line between the axial point and the midpoint of the inferior border of the carotid fossa to ensure the blood flow of the flap. Depending on the size of the wound to be repaired and the length of the tip, the flap should be designed on both sides of the axis. Depending on the shape and size of the wound, the flap is designed on the donor axis.
The flap is designed on the donor area axis according to the shape and size of the wound. The flap size should be approximately 10% to 15% larger than the trauma size, and the flap donor area should be located on the posterior side of the calf near and in the middle. The maximum flap size can be 16 cm × 9 cm.
Third, flap excision
The use of a pneumatic tourniquet, without or with partial expulsion of blood, facilitates the identification of the small saphenous vein. The flap is cut by the retrograde method
The proximal end of the flap is first cut to the deep fascia layer to reveal the proximal end of the gastrocnemius nerve and its nutrient vessels, then the skin on both sides of the flap is cut to the deep fascia layer, and the proximal end of the gastrocnemius nerve and its nutrient vessels and the small saphenous vein are ligated, and the flap is separated from the subfascial part to the tip.
The flap is lifted. Take care not to separate the fascia from the skin by fixation. The skin between the flap and the rotation point is incised at the proximal end of the flap, and the flap is separated under the dermis about 2 to 3 cm wide on each side.
With the medial gastrocnemius nerve and its nutrient vessel tip as the axis, the 1.5-2 cm wide subcutaneous fatty tissue and deep fascia on both sides are retained within the tip.
The position of the anastomotic branch is observed near the rotation point to avoid injury. In the upper part of the calf, the gastrocnemius nerve is divided into the medial and lateral gastrocnemius nerves, which are approximately 3 cm apart, with the medial gastrocnemius nerve running in the deep surface of the deep fascia.
When the flap area is small, the lateral gastrocnemius nerve may not be included in the flap or tip, which forms a retrograde flap with fascial tip of the gastrocnemius nerve trophic vessels, which is transferred to the recipient area through an open tunnel flap, and the donor wound is directly sutured or repaired with a skin graft.
IV. Surgical points and precautions
1. Increase the width of the fascial tip of the flap, not less than 3-4 cm, because there are three arteries and accompanying venous branches around the ankle joint, including the anterior tibial, posterior and peroneal arteries, which constitute the vascular network around the ankle joint.
The width of the tip increases the number of vessels in the tip, which not only ensures the arterial blood supply of the flap but also facilitates the venous reflux.
2.Ensure the width of the tip, open the tunnel and choose the appropriate rotation direction and rotation point according to the location of the wound to prevent the twisting of the tip.
3.When packing the donor wound implant and postoperative dressing, avoid pressure on the tip.
4.Prevent the stretching of the tip, and design the flap fascial tip appropriately longer to prevent the stretching from endangering the blood supply of the flap.
5, to ensure the height of the rotation point of the tip, to prevent too low damage to the peroneal artery through the branch, affecting the blood supply. Through the above measures, a larger retrograde peroneal nerve trophic vascular flap can be cut, which allows the flap to be repaired to a greater extent.
The flap can be cut to a larger size, overcoming the previous problem that the flap could not be cut to a larger size and its application was limited.
The rotation axis of the flap is the line between the midpoint of the outer ankle and Achilles tendon and the midpoint of the N fossa.
7. The rotation point of the retrograde flap should not be lower than 5 cm above the outer ankle.
Before surgery, carefully mark the rotation axis and rotation point with gentian violet, measure the distance from the rotation point to the wound, and also measure the length of the flap tip, and the part of the flap, and the size, which should be 0.5-1 cm larger than the actual defect.
8, The tip is cut with some fascia (2 – 3 cm) to prevent damage to the nutrient vessels. It is safer to use a bright transfer, and the tip must not be pressurized, and if necessary, the tip should be implanted.
9, when the flap is cut, the skin and subcutaneous and fascia should be cut together, and the fascia and skin should be intermittently sutured to prevent their separation. The proximal end of the flap should be ligated to cut the small saphenous vein and the medial peroneal nerve.
V. Pre-operative and post-operative treatment
Follow the principles of vascular surgery as much as possible, and quit smoking 2 weeks before surgery. Elevate the affected limb after surgery to improve reflux. Keep the affected limb warm to prevent small vessel spasm. For 3 weeks after surgery, prohibit ground activities and stop smoking, etc. are conducive to flap survival.
Sixth, postoperative care
1, postoperative care: postoperative braking of the affected limb, elevated 20 cm above the heart; forbid the affected limb to be placed on the edge of the bed; dorsal and plantar flap transfer to the flat position; medial and epicondylar flap transfer to the healthy side; heel flap transfer to the side prone position.
2, flap care: blood flow observation: after flap transfer, the flap capillary filling expansion, skin color is slightly red compared with the skin of the donor area, the flap is mildly swollen, capillary filling response is rapid, the time is 1~2 seconds, skin tension is moderate, and skin lines are visible. Skin temperature measurement: skin temperature is one of the indicators to evaluate the good or bad blood circulation in the capillary bed. The skin temperature should be measured regularly, positioned, and compared with the skin temperature of the fixed part of the healthy limb, and also consider the influence of room temperature, local ambient temperature and the size of the flap on the skin temperature, and stop illuminating infrared light for 2-3 minutes when measuring. The blood flow of the flap and the skin temperature should be recorded every 1 hour for 3 days after surgery, and can be stopped after 2 weeks of surgery.
3.Observation and treatment of vascular crisis: vascular crisis mostly occurs in 6~72h after surgery, therefore, timely observation and early treatment should be made. ①Vasospasm: cold, nicotine and pain can lead to vasospasm of the flap. Therefore, postoperative application of baking lamp irradiation for local warmth at 25-30℃ for 10-14 days; strengthening anti-smoking education, timely injection of analgesic to relieve pain; 1 intramuscular injection of poppy bases 30mg every 6 hours to help dilate blood vessels. ② Arterial crisis: pale or gray flap color, dry flap tissue without tension, capillary filling time is delayed or disappeared, flap temperature is more than 3℃ below normal skin, slow needle bleeding, dark red color or no blood outflow is arterial crisis. If it is caused by the compression of the vessel tip, the position should be corrected in time to release the compression; if the blood supply is insufficient due to the distortion of the vessel tip, the doctor should be notified immediately for surgical investigation. ③Venous crisis: if the flap is purple-red in color, high tension, fast capillary filling time, scattered blisters, active needle bleeding, and the color changes from dark red to bright red after bleeding and there is increased localized bleeding, it is venous crisis. Care should first observe the dressing wrapping situation, if caused by dressing wrapping too tight, should immediately loosen the too tight dressing, so that the limb is placed in the position of relaxation of the vascular tip; if the flap tension is too high, should remove part of the flap edge suture away from the tip, take blood drip therapy until the tension returns to normal; if the bleeding around the skin edge is not much, and there is a trend of natural hemostasis, does not affect the circulation, can continue to closely observe.
4, the care of the donor area: within 15 days of the dressing of the skin extraction area, it is necessary to observe whether the dressing dressing is loose and falls off, whether the wound dressing has signs of blood and ooze and whether there are signs of infection such as odor, and whether the skin feels normal.