Abstract OBJECTIVE: To summarize the method of expanding the area of the small saphenous vein-peroneal nerve trophic vascular fascial flap and to explore the characteristics of the flap blood supply and clinical application. METHODS: A retrospective analysis was performed on 26 cases of large-area flaps with an area of 16 cm×10 cm~25 cm×16 cm for repair of postoperative bone exposure with infection and bone discontinuity in calf fractures; long-term non-healing anterior tibial skin ulcers; open ankle fracture dislocation with tendon exposure; heel skin defect with Achilles tendon rupture dorsal foot skin defect with tendon bone exposure. RESULTS: At 5-37 months of follow-up, all flaps were viable except for 2 cases with a little epidermal necrosis at the distal edge, with no recurrence of infection; fracture healing; and satisfactory cosmetic and functional recovery. Conclusion: The expanded flap with reliable blood supply and no injury to important blood vessels is an ideal method for repairing skin and soft tissue defects in the calf and foot and ankle, and is especially suitable when combined with major vascular injuries in the calf. Wang Weiguo, Department of Orthopaedic Trauma, Jinan Military General Hospital, Jinan, China Keywords Skin flap; Small Saphenous Vein – Peroneal Nerve; Repair Methods and Clinical Application of enlarging Flap Supplied by Vascular Axis of Small Sapheonus Vein and Sural Nerve Abstract Objective: To sum up the methods of enlarging flap supplied by the vascular axis of the small suphenous vein Methods: A retrospective study was made on 26 cases of leg fractures with skin defect and infection, chronic ulcer or soft tissue defect in legs, heel skin defect with severed Achillis tendon and ankle opening fracture and dislocation and skin defect of dorsum of foot with exposed tendons, which were repaired with flaps from 16cm×10cm to 25cm×16cm . Results: All the flaps survived completely except 1 case with small necrosis at the distal edge. After a follow up of 5 to 37 months, all fractures were healed and no ulcer or infection. The appearances of the flaps were satisfactory. Conclusions: The enlarging flap with reliable blood supply It is an ideal method for repairing the soft tissue defect in leg, ankle and foot with the flap especially when accompanied with the main vessel impairment. Key Words Flap; Small Sapheonus Vein and Sural Nerve; Repairation In 1992 Masquelet first reported 6 cases of insular flap with peroneal nerve as the tip. However, the maximum area was only 5 cm × 3 cm, so its clinical application was limited. Since then, there have been many reports on the clinical application of dermatomal neurotrophic vascular flaps in the extremities, and in 1998, some authors concluded that the safe excision range of this flap could reach 17×12 cm through experimental and anatomical studies, and in 2001, another author proposed a safe excision range of 20×13 cm, but the clinical application was below 16 cm×10 cm. From October 2000 to August 2009, we used retrograde small saphenous vein-peroneal nerve trophic vascular flap to repair soft tissue defects in the calf, ankle, heel, and dorsum of the foot in 58 cases, of which 26 cases were larger flaps with an area of 16 cm × 10 cm to 25 × 16 cm, with satisfactory clinical results, as reported below: 1. Clinical Data 1.1 General Data The 26 cases in this group, 20 males and 6 females, aged 9 to 58 cm, had a safe cut range of 17 × 12 cm. Female 6 cases, age 9-58 years old. Injuries and sites: 6 cases of skin necrosis, defective plate exposure and infection after internal fixation of tibiofibular fracture plate; 4 cases of tibial fracture with bone scar and bone exposure; 3 cases of pretibial skin ulceration; 4 cases of pretibial skin necrosis and infection after dislocation of dorsal ankle artery, pretibial, extensor [and extensor tendon rupture; 4 cases of dorsal foot traumatic skin defect with bone joint and tendon exposure; 4 cases of heel skin defect in 2 cases, and skin defect of Achilles tendon rupture in 3 cases. The maximum flap area was 25cm×16cm and the minimum was 16cm×10cm, all of them were retrograde transfer, except for 3 cases with island flap, all of them were peninsular flap. 1.2 Surgical method The gastrocnemius nerve and its accompanying small saphenous vein were used as the central axis of the flap, and the rotation point of the tip depended on the site of the wound repaired by the flap, if necessary, according to preoperative Doppler ultrasound detection and careful intraoperative anatomical observation, the rotation point could be appropriately shifted downward, generally not lower than 5 cm above the outer ankle, in order not to damage the peroneal artery perforating the outer ankle. The upper border of the flap is usually not more than 3 cm below the plane of the peroneal tuberosity, and the width of both sides can reach 1/2 of the circumference of the calf with the peroneal nerve as the axis, the incision starts from the upper border of the flap, cut to the deep subfascial ligation of the small saphenous vein, and look for the medial peroneal cutaneous nerve at the intermuscular groove of the gastrocnemius muscle, usually the two accompanying lines walk distally, because the area of this group of flaps is large, so the width of the tip is more than 3-4 cm, and the distal side of the flap contains the medial peroneal cutaneous nerve and the peroneal nerve traffic branch two nerve. Except for two cases where the repair wound was small and made into an island flap, all other flaps were peninsula-shaped flaps, i.e., the skin and fascial tip were of equal width, and the skin was sutured to the skin edge on both sides by transferring the surface with a bright channel to avoid pressure on the tip affecting blood flow. Drainage strips were routinely left between the flap and the trauma. Patients with intra-articular infection, tendon outgrowth trauma infection, and osteomyelitis were repeatedly flushed with antibiotic solution intraoperatively, and those with more exudation were drained until the exudation was significantly reduced or basically disappeared before the drainage was removed. 2. Results All 26 cases in this group were followed up for 5 months to 37 months. Except for 2 cases of postoperative epidermal necrosis at the distal end of the flap, which healed with drug replacement, all the flaps were viable. 3 patients with osteomyelitis and other local skin ulcers, open joint infections, and tendon outgrowth infections were healed, and bone defects and osteoconnective implants were also healed. In one case of an 8-year-old child with dorsal foot skin defect, tendon and bone exposure, a deformity of the 3rd to 5th toe supination was seen at the 2-year postoperative follow-up, probably due to scar contracture under the flap. 3. Typical case 1 Patient, male, 28 years old, had an open fracture of the left tibiofibula caused by a car accident on 2000-07-13, and underwent debridement and suture plate internal fixation at a local hospital. Postoperatively, the skin of the anterior medial aspect of the left calf was necrotic, the trauma was infected, and the plate and bone were exposed. After treatment with drug changes, anti-infection and adequate drainage, debridement, plate removal, external fixation frame fixation, and trauma skin grafting were performed 4 months after surgery (at that time The skin implanted was mostly viable, but partially necrotic, and the remaining trauma was mostly closed after 2 months of drug exchange, but 0.8cm×0.5cm of bone was still left exposed. On September 10, 2001, he came to our hospital and underwent debridement of the fracture end of the anterior medial apposed bone scar of the left calf, bone grafting of the iliac bone defect, and transfer of the small saphenous vein – gastrocnemius nerve trophic vascular fasciocutaneous flap (16cm×10cm) to repair the wound after surgery. The external fixation frame was removed after 8 months, and the fracture healed well. The left ankle flexion and extension range: 90º-90º-125º, with mild claudication during walking. Typical case 2 The patient, male, 45 years old, was admitted to the hospital on 2001-4-26 with a 3-year non-healing medial anterior tibial ulcer on the lateral side of the left calf. On examination, he saw a 6-cm×5-cm skin ulcer on the left calf, with obvious skin pigmentation and hard texture, and varicose saphenous vein on the left lower limb. The skin and subcutaneous tissues around the ulcer were extensively fibrotic, hard and tough, rust colored, with multiple dilated veins, and the skin was cleared to normal skin, with a trauma area of 23cm×14cm, and a flap area of 25cm×16cm was taken to cover the trauma, and the secondary trauma was repaired with free skin implants. The stitches were removed in half a month and the wound healed in one stage, but there was swelling of the left foot after walking on the ground. After discharge from the hospital, he was instructed to gradually increase the walking time, wear elastic stockings and strengthen the calf muscles, and the swelling of the foot basically disappeared after six months of review. 4. Discussion 4.1 Measures for flap blood supply and increasing flap area The flap has four sets of blood supply systems: ① peroneal nerve nutrient vessels. The gastrocnemius nerve has multiple and constant blood sources, the arteries are stage-distributed and have extensive anastomosis with each other, the proximal part of which is issued by the well-known artery accompanied by the action vein, with a thick outer diameter and a long tip with a long distance from the nerve stem, the trophic artery of the gastrocnemius nerve comes from the myocutaneous branch of the peroneal artery, with an average of 3 branches, such as the small head of the fibula to the outer ankle is divided into 8 parts, the uppermost being the first region and the lowermost being the eighth region, each about 4.4 The medial peroneal cutaneous nerve and peroneal nerve traffic branches are supplied by the arteries from five arteries, including the myocutaneous branch of the N artery, the myocutaneous branch of the posterior tibial artery, the cutaneous branch of the tibial artery and the medial and lateral peroneal arteries. Masquelet suggests that although these small arteries have a limited blood supply and only nourish one segment of the nerve, just like one leg of a relay race, the interlacing net work of many small arteries through the mutual anastomosis of the branches, which forms a longitudinal interlacing net work, significantly expands the blood supply range and distance to nourish long segments of the cutaneous nerve and skin. The longitudinal interlacing net work significantly extends the range and distance of blood supply to the long dermal nerve and skin. In 1998, Nakajnna’s study on superficial veins and dermal nerves of the extremities found that superficial veins of the extremities, like dermal nerves, also have their own vascular system of nutrients, i.e., there are longitudinal extrinsic venocutaneous vascular system and superficial venous wall vascular network along the dermal nerve trunk. （The superficial venocutaneous vascular system has its own nutrient vascular system, namely the longitudinal extrinsic venocutaneous vascular system and the intrinsic venocutaneous vascular system along the dermal nerve trunk.) In the area where the superficial vein is closely associated with the dermatomal nerve, the paracentral vascular network of the dermatomal nerve and the superficial paracentral vascular network converge to form a common trunk, and the hair branch is associated with the dermatomal trunk vascular network, and the complicating branch nourishes the nearby skin. (3) Peroneal artery penetration branch. The perforating branches are mostly issued 4.5~12 cm above the outer ankle with an average of 3 branches. (iv) The vascular network around the ankle joint. Therefore, this flap is called the small saphenous vein-peroneal nerve trophic vascular fascial flap, which can more accurately reflect the blood supply characteristics of the flap. Protecting these blood supply systems as much as possible is the basis to ensure the normal operation of the flap blood circulation. However, traumatic tissue injury is complex and changeable, sometimes it is difficult to ensure the integrity of 4 sets of blood supply systems. In this group of cases, there were 2 cases of small saphenous vein injury, 2 cases of gastrocnemius nerve dissection, 1 case each of medial peroneal cutaneous nerve and peroneal nerve traffic branch dissection, and 1 case of lateral calf soft tissue injury resulting in peroneal artery perforator injury, but no circulatory disorder occurred after flap free, which means that as long as 3/4 sets of blood supply systems are guaranteed, the flap blood circulation will no problem. In this group, the largest flap area was 25cm×16cm, and the farthest flap was cut below the fibular tuberosity, and the farthest repair was made to the metatarsal head, and no obvious blood flow obstruction occurred, we mainly took the following measures: ① The flap was made into a peninsula shape, that is, the skin of the tip was not cut off, the skin of the tip and the subcutaneous fascia were equal in width, and Mingdao rotated the flap, which ensured the subdermal vascular network and made the tip more relaxed, so that it was not compressed and caused circulatory obstruction. The width of the tip is increased when the flap is large, generally not less than 3 to 4 cm, and there are three thick arterial branches around the ankle, such as the anterior tibial, posterior tibial and peroneal arteries, which intertwine to form the peri-ankle network, and increasing the width of the tip increases the number of vascular networks in the tip, which is not only beneficial to the arterial blood supply of the flap, but also to its venous return. In one case of this group, the anterior tibial skin ulcer had not healed for 3 years, and the area after debridement reached 23 cm×14 cm. A flap of 25 cm×16 cm in size was taken, and the flap was free to 6 cm above the outer ankle, and a thicker perforating branch was seen, which was transferred here as a rotation point. Although the soft tissues in front of the tibia were severely lesioned due to the long-term non-healing ulcer, and the skin around the flap could only reach the level close to normal tissue after debridement, the flap had good blood flow and balanced arteriovenous ratio after surgery, and the wound healed at stage I. The gastrocnemius nerve is composed of two longitudinal cutaneous nerves that converge in the lower and middle calf, which can nourish the skin as well as the blood vessels. ④ Ensure that the tip is loose and that the skin margin on both sides is appropriately freed for the Ming tract transfer, or excised if it is a scar. Choose to rotate the flap clockwise or counterclockwise according to the location of the trauma, choose the appropriate rotation point to minimize the rotation arc, and avoid pressure on the tip to prevent the blood flow of the flap when packing the trauma implant in the donor area and postoperative dressing. 4.2 Treatment of infected trauma of bone and joint, bone defect and bone scar: The survival of the flap may be affected by the toxic effect of inflammatory substances when flap transfer is performed to cover trauma with severe infection and purulent exudate before the infection is controlled. Therefore, preoperative treatment of infected wounds should be active, with timely dressing changes and selection of appropriate antibiotics, and drainage of infected wounds with a lot of purulent exudate should be enhanced by changing the body position and other measures. After the infection is controlled, choose the appropriate time for surgery. With thorough intraoperative debridement, adequate postoperative drainage, and removal of drainage when the secretion is significantly reduced, and the strong anti-infection ability of skin flaps with good blood flow, the control of bone and joint infection is not difficult. For the bone scar and bone defect, the scar should be completely removed because necrosis can occur with a slight peeling of the bone scar, and the fracture end should be cleared until the blood is actively oozing, and the bone graft should be covered with a skin flap, because the skin flap has sufficient blood supply, which is conducive to the establishment of circulation with the bone injury and is very beneficial to promote the healing of the bone graft. 4.3 Treatment of heel flap rupture and skin defect: Free flap while cutting gastrocnemius stop tendon, gastrocnemius muscle membrane, medial and lateral cephalic interval and part of muscle tissue can repair Achilles tendon defect, muscle tissue filling in Achilles tendon defect can occur muscle Achilles tendonization, histological structure and biomechanical properties are similar to Achilles tendon tissue, which can basically satisfy the need of Achilles tendon function. Three patients in our group took this method to repair the Achilles tendon and skin defects, and the functional recovery was satisfactory in the postoperative follow-up. 4.4 Treatment of postoperative foot swelling: Since the flap must cut the small saphenous vein, and some of the saphenous veins at the anterior ankle or anterior tibial trauma have been damaged, so when the flap is applied, the two major superficial veins of the lower leg cannot return blood, and in addition, the muscles of the lower limbs are relaxed after the injury and long-term bed rest after surgery, so these patients will have foot swelling in the early stage of wound healing and walking on the ground, as long as the deep veins of the lower limbs are intact and undamaged. As long as the deep veins of the lower extremities are intact and the muscle strength exercise of the lower extremities is strengthened, supplemented by wearing elastic stockings and applying intravenous pumps, the swelling of the patient’s feet can be effectively controlled after the compensatory function of the superficial veins and deep veins is gradually improved, which does not affect normal work and life. Most of the swelling of the foot disappeared or improved significantly at the follow-up of all cases in this group. The flap can be flexibly adjusted within a certain range, and the flap can be rotated clockwise or counterclockwise according to the trauma site, which is very convenient for application. The retrograde flap can repair various soft tissue defects from the mid calf to the area near the metatarsal head, and the flap can be cut in a wide and safe range, which is of great value to meet the repair of larger trauma on the anterior tibia, ankle, heel and back of the foot. In this group, the largest flap was cut to 25 cm × 16 cm without circulatory disturbance. The flap has balanced arterial and venous circulation and is resistant to infection. The flap was cut under deep fascia, superficial location, and simple operation, but when cutting larger flaps, the tip needs to be widened appropriately, sometimes slightly bloated, in addition to the need to sacrifice a cutaneous nerve, which has a certain impact on the lateral sensation of the dorsal foot. Many flaps with the major blood vessels of the extremities as the tip have to sacrifice the dermal nerve within the flap, resulting in a certain range of dermal sensory deficits. In contrast, the present flap is of greater clinical value because it sacrifices one less important vessel.