The fibula is located at the lateral side of the calf, and it is not the important load-bearing bone of the calf. Its lower one fourth participates in the composition of the ankle joint and plays a role in strengthening joint stability. The average length of fibula is about 34 cm, the upper end of fibula is expanded into the fibular head and is not directly involved in the composition of the knee joint, and it can be used in condylar reconstruction in clinics. The maximum length of fibula available for harvesting is 26 cm. The fibula has dual bone cortexes, the upper segment of its cross section is quadrilateral, the lower segment is triangular, and the appearance is constant. The average diameter of the middle segment of the fibula in Chinese people is 12.8 ± 2.4 mm in males and 11.1 ± 2.0 mm in females, respectively, which can meet the need of the implant retention. The bicortical structure can also enhance the stability of the implant.

The blood supply of the fibular osteocutaneous flap comes from the peroneal artery and its two accompanying veins. Under normal circumstances, the popliteal artery is bifurcated into the anterior tibial artery and the posterior tibial artery, and the posterior tibial artery gives off the peroneal artery; the peroneal artery and its accompanying veins run down between the flexor pollicis longus and posterior tibial muscle at the medial side of the calf. However, the blood supply of the fibula sometimes has some anatomical variations according to researches by scholars at home and abroad. Understanding these anatomical variations helps to avoid ischemic complications in feet.

The study of Wu Yongmu et al. on 100 Chinese peoples showed that the peroneal arteries are divided into four types according to different starting points: type I is given off from posterior tibial artery, accounting for 90%; types II and III are given off separately from the anterior tibial artery and the popliteal artery, each accounting for 1%; and type IV peroneal artery is absent and is replaced by the posterior tibial artery, accounting for about 8%. If the blood vessels are blindly ligated, the blood supply disorder of posterior calf muscle group may occur; at the same time, if the diameter of the anterior tibial artery is small, a phenomenon such as foot ischemia may occur. The blood supply of the fibula is characterized by the dual blood supply system of periosteum and bone marrow; namely, the fibular nutrient artery and the arcuate artery reach the bone marrow cavity, periosteum, and bone cortex of the fibula, respectively. In most cases, there is only one fibular nutrient artery; it passes through the nutrient foramen at the medial side of the fibula to enter into the bone marrow cavity to constitute the blood supply of the fibular bone marrow, providing nutrition to the bone marrow and a part of the bone cortex. There are 4–15 arcuate arteries, which are segmentally distributed along the fibula and clinging to the periosteal surface and constitute the periosteal artery network, and they are the sources of blood supply to adjacent periosteums and muscles. Even if the single source of blood supply such as the periosteum branch of the arcuate artery is retained, the fibula still can survive. This is also the anatomical basis for that multiple segmental wedge resections of the fibula flap which can be performed in clinics, and each bone segment still has sufficient blood supply.

In addition to the nutrient artery of the fibula and the muscle – periosteum vessels, it is observed that the peroneal artery and its veins also include the fasciocutaneous perforator traveling within the intermuscular space at the posterior side of calf to feed the skin in this region. Wherein, there are three thick and constant cutaneous branches at 9–20 cm below the fibular head, and the outer diameter is about 1.6 mm, which is the anatomical basis for clinical preparation of fibular flap. The in-depth studies of many scholars prove that the lateral calf skin is fed by the intermuscular space perforators of the peroneal artery; these perforators are divided into the following three types: type A, the intramuscular perforator, passes through the long peroneal muscle to reach the lateral calf skin, with no muscle branches, and is located mostly in the proximal and middle one third of the thigh; type B is also an intramuscular perforator, passes through the gastrocnemius muscle and long peroneal muscle, and gives off muscle branches before reaching the skin; and for type C, its running direction is similar to that of the type B, but it gives off the space perforator instead of the intramuscular perforator, which is mostly located in the middle and distal one third of the calf.

The study of Beppu on the distribution of blood vessel perforators in lateral calf skins of 23 patients showed that a perforator was located very constantly in the midpoint of connecting line between the fibular head and the lateral malleolus. Among the 23 patients, it was found that a perforator was located at a site within 2 cm near the midpoint in 21 patients and the blood supply provided by the peroneal artery to the proximal one third of the lateral calf skin was not constant. In the anatomies of 23 patients, the peroneal artery had no perforator supplying blood to the proximal one third of the lateral calf skin in 5 patients. While in the anatomies of 23 patients, there was at least one skin separating perforator at the middle one third of the calf. But the anatomical studies of some authors suggested that about 20% of the samples did not support the existence of the skin separating perforator and 6–25% of the samples had no muscle and muscle separating blood vessels at the same time. Therefore, it is now considered that the absolute confidence level of fibular flap is 93–94%. Although the reliability of the blood supply to the skin island is still controversial, according to Wei’s report, in which the fibular flap was used in the reconstruction of 80 cases of limbs and 27 cases of mandible, the skin island had achieved a 100% successful survival rate. The author designed the center of the island design at the junction of middle one third and distal one third of the fibula and emphasized that the intermuscular space at the posterior side of calf must be included in the skin island; the operator should not pull too much in the process of flap preparation and wound closure, so as not to damage the blood supply of the skin island. Currently, most scholars adopt the method of Fleming for preparing the skin island of fibular flap, and that is to dissect at the level under the fascia from anterior to posterior. In order to be able to adapt to and accommodate possible variation in the position of intermuscular space perforators, a longer skin island can be designed. If there is no existence of the skin separating perforator, it is required to look for the myocutaneous perforator supplying blood to the skin. If there is no myocutaneous perforator given off from the peroneal artery, it indicates a need to select another separate soft tissue flap to repair the soft tissue defects. In the patients with skin separating perforators, part of muscular sleeves of flexor hallucis longus muscle and soleus muscle should also be carried, because when converging into the peroneal artery, these perforators may pass through these muscles, but the sizes of the harvested muscle sleeves should be appropriate.

The results of the study on injecting dye into the peroneal artery indicate that the average width of stained skin area is 9.9 cm and the length is 21.4 cm. Fleming successfully divided the skin island into two parts through incising the skin instead of incising the fascia.

The sensation in lateral calf skin comes from the lateral sural cutaneous nerve, which comes from the common peroneal nerve, while the common peroneal nerve is divided into the deep peroneal nerve and the superficial peroneal nerve at the fibular neck, which control, respectively, the anterior muscle group and lateral muscle group in the calf. The common peroneal nerve gives off a pair of cutaneous nerves at the outer side of the popliteal space, namely, lateral sural cutaneous nerve and the sural communicating nerve; the lateral sural cutaneous nerve controls the lateral and posterior skins in the calf. But some scholars have reported that the large lateral sural cutaneous nerve has a great variation; 22% of people lack this nerve. The sural communicating nerve is the second sensory nerve crossing the area of fibular flap, and it combines with the medial sural cutaneous nerve into the sural nerve. In clinic, according to this dissection method, the lateral sural cutaneous nerve or sural nerve is anastomosed with the lingual nerve or inferior alveolar nerve, which may restore sensory function.

There are three types of anatomical variations:

The harvested fibular myocutaneous flap needs to be fixed with the reconstruction plate or the titanium plate, the fibula can be fixed only at the outer side of the fibula. And because the vascular pedicle of fibular flap is relatively short, the location needs to be designed near the mandibular angle as much as possible. Therefore, under normal circumstances, the repair of the unilateral mandibular body requires taking the contralateral calf as the donor site; the calf at the side with more defects will be selected as the donor site for repair of the anterior mandibular defect; the calf at the side of the cervical blood supplying vessels will be selected as the donor site for repair of the bilateral defects. The positioning can meet the requirement that the strong internal fixation is performed in lateral side, and the implanted implant in the upper margin does not damage the blood vessels.

Due to the limitation of the anatomical structure, the vascular pedicle of the fibular myocutaneous flap is generally shorter. The more distal osseo-myocutaneous flap will be harvested in clinics. Meanwhile, the mesial parts of periosteum and the vascular pedicle are stripped off downward, and the proximal middle bone segment is removed, so that the vascular pedicle may be extended. Hidalgo et al. [3] reported that a vascular pedicle of approximately 13 cm long can be obtained using this method. In addition, there is no significant difference in diameter between the proximal and distal ends of the peroneal artery and vein, so that the fibular flap can be used as a bridge flap. To repair a greater range of soft tissue defects, the tandem skin flap is formed when a free soft tissue flap is connected at the distal ends of the peroneal artery and vein on the fibular flap.

In order to meet the requirements for denture repair or requirements for implantation of bone fusion implant after surgery, the scholars at home and abroad increase the height of alveolar crest with the method of placement and fixation of double layers of fibula, so that the requirements for facial appearance and function after repair can be satisfactorily met. In addition, in China, Zhang Chenping applied the distraction osteogenesis techniques in stretching of the fibular flap, designed the vertical distraction of fibula built-in dental implant combining two technical advantages such as implantation and distraction osteogenesis, achieved the purpose of increasing the height of alveolar crest, and obtained ideal results.

If it is needed to prepare the fibular myocutaneous flap with sensory nerve, the osseo-myocutaneous flap with sural nerve can also be prepared, and the traffic branch of the nerve can be anastomosed with the inferior alveolar nerve to restore the sensation of fibular myocutaneous flap.

According to the anatomical characteristics of the lateral calf, the corresponding anatomical landmarks are marked on its outer side. The landmark points of the muscular clearance are the fibular head in the upper part of the calf and lateral malleolus in the lower part of the calf, and the connecting line between two points is the position of the intermuscular space at the posterior part of the calf. If the skin island is needed simultaneously, it can be designed as spindle shaped, and its midline is the position of the intermuscular space. Since the main perforator of the skin flap is usually located in a slightly remote location of the calf, the central point of the skin flap is typically designed at the junction of middle and distal one thirds of the calf.

After the landmark points are drawn, that is, the dissection is started after the 350 mmHg balloon or tourniquet is wrapped around the thigh (the time of usage of tourniquet is controlled within 1–1.5 h). According to the designed incision line, incise the skin and subcutaneous tissue and the fascia on the superficial surface of the long and short fibular muscles; after that, dissect at the deep surface of this fascia from anterior to posterior and toward the direction of intermuscular space; at the moment, it is easy to find the myocutaneous perforator given off from the area near the inferior margin of fibula; the position of the skin island can be redefined according to the position of the flap perforator. After that, sharply dissect along the superficial surface of the outer periosteum of fibula, and turn up the long fibular muscle, short fibular muscle, and extensor hallucis longus; the osteotomy is performed, respectively, at the proximal middle and distal middle part of the fibula, the interosseous membrane is further dissected and exposed along the medial surface of the fibula, and the distal portions of the peroneal artery and vein are dissected out through pulling the fibula and then are ligated and cut off. Afterward, the posterior margin of the skin flap is incised at the surface of the gastrocnemius muscle and the soleus muscle to reach to the deep surface of the fascia, and the dissection is performed along this surface, and the skin island with myocutaneous perforator can be formed. This skin island can be temporarily fixed on the fibular bone flap with a needle for fear that the perforator is pulled to affect the survival of the skin island. Then the bone flap is pulled outward, and the interlaced posterior tibial muscle fibers are incised along the inner side of the peroneal artery and vein toward the direction of the proximal middle part, while the branches of the peroneal artery and vein between and within the muscle fibers are ligated and cut off to the bifurcation site of peroneal artery and the posterior tibial artery. The flexor hallucis longus must be cut off in this process, only part of the muscle sleeve is retained on the fibula, the vascular pedicle is cut off, and the fibular myocutaneous flap with a peroneal artery and two accompanying veins is formed. Because of the need to protect the vascular pedicle, the tissue flap carries part flexor hallucis longus and tibialis posterior muscle sleeves.

In the preparation of fibular bone flap, in order to avoid damage to the peroneal nerve and maintain the stability of the ankle joint, about 7 cm long bone segments must be retained, respectively, at the proximal and distal ends of the fibula. Attention must be paid to protecting the deep peroneal nerve passing through the neighboring area.

If it is needed to prepare the fibular myocutaneous flap with sensory nerve, the lateral sural cutaneous nerve given off by the common peroneal nerve must be tracked toward the mesial direction before the posterior margin of the skin flap is incised. After this nerve is found, the skin island can be reached along the nerve. The sural communicating branch can be given off at this site from the common peroneal nerve, but this nerve does not control the sensory function of this skin island and can be included into the skin island for vascularized nerve transplantation [2, 13].

At present, most domestic scholars adopt the latter two methods; now the selection can also be based on the habits, experiences, and skill levels of the surgeons.