The fasciocutaneous flap from the sural region of the lower leg has been extensively investigated in respect to vascularization and the concept of neurocutaneous flaps. However, the reconstruction of heel defects remains limited and problems can occur by using these possibilities. Anatomical studies have showed a three-dimensional vascular architecture of the posterior lower leg integument from the superficial sural artery, the septocutaneous perforators, peroneal artery, and myocutaneous perforators. There is prominent longitudinal orientation or axiality of the circulation of the facial, paraneural (sural nerve), and perivenous (lesser saphenous vein) vascular plexuses. There are also 4 to 5 axial communications between this longitudinal neuro-veno-adipofascial plexus and the posterolateral septocutaneous perforators issued from the peroneal artery[12,13] With distal axial perforator perfusion, blood flow can reach a long distance in the lower-resistance longitudinal vascular plexuses and results in survival of a large flap without arterial ischemia.
Because of the anastomosis between the peroneal artery perforator and the longitudinally oriented median suprafascial sural artery, this type of flap can be based not only proximally, but also distally[1417] This flap has been designed with a long and narrow pedicle and a wide arc of rotation, because its vascular axis has the largest direct artery of the posterior calf and strongest peroneal perforator at its pivot point. This allows elevation of the skin supplied by this neurovascular axis as a flap for coverage of leg wounds, with the entire flap being axial in nature.
Recent modifications of distally based perforator sural flap overcame most of the drawbacks of the original technique. Ayyappan et al.,[11] introduced the super sural flap, harvesting all available tissues in the upper third of the leg, and just preserving 1 to 2 cm of skin from the popliteal crease. The length of the pedicle or size of the flap influenced neither congestion nor survival of the flap. Chang et al.,[18] and Zhang et al.,[19] reported their clinical experience on the transfer of distally based sural flap with a lower vascular pivot point. They demonstrated that the blood supply of the distally based sural neuro-veno-fasciocutaneous flap can be pivoted at lower perforators in the posterolateral region, which are about 3 and 1 cm proximal to the tip of the lateral malleolus. The greatest length of the flap in those series was 30 cm, and it survived completely without complications.
In our study, we designed a longitudinal S-shaped flap which its proximal end extended well beyond the conventional confines into the upper third of the leg. The width of “S” considered was about 55% of the horizontal dimension of the recipient site and its length was twice the vertical dimension of the defect. The additional 5% of flap area can compensate the probable shrinkage of flap after harvesting. In the current technique, the width of the flap was gradually increased from 1.5 cm to 3.5 cm. The inclusion of skin over the shorter pedicle facilitated better manipulation of the flap, increased margin of safety, avoided the dog-ear deformity, and reduced morbidity at the donor site. In this technique the flap is a type A fasciocutaneous flap which is innervated by the medial sural cutaneous nerve (s1–2), and the lateral nerve is not involved. All flaps survived with no complication and wound healing was complete at the donor site. Additionally, the pedicle of the flap was supported by the distal portion of the flap itself, so the tension on the pedicle and the pivot point was relieved.
In previous studies, the major disadvantage of reverse sural flap was an unsightly scar over the posterior calf when a fasciocutaneous flap was used. This problem can be avoided by taking only the fascia and covering it with a skin graft. The neurologic deficit caused by the sacrifice of the sural nerve is negligible. The distally based neurocutaneous sural flap is an excellent choice in the pediatric age group for covering defects of the lower leg and foot, where thin pliable skin is needed. The aesthetic outcome of the flap transfer might be unsatisfactory, especially in females and children.
In our modifications, this shape of the flap relieved the tension on the suture line and prevented the possibility of scar contracture deformity. The surgical defect of the donor site could be closed primarily, as skin graft was not necessary. Therefore, the duration of aesthetic reconstruction and hospital stay decreased. Rehabilitation started sooner and patients were quite satisfied.
In conclusion, this modified S-shaped sural flap can be applied safely and reliably for reconstruction of foot and ankle defects with favorable aesthetic outcome. Regarding the simplicity of the dissection and flap transfer and low morbidity rate it seems that this modified technique could be a good choice in complex defects of the lower limb. However, it needs further investigations.