Septocutaneous Vascularized Sural Nerve Free Flap for Simultaneous Reconstruction of Nerve and Thin Soft-Tissue Defects

Combined extended nerve and soft-tissue defects, e.g., after high-voltage injuries, require nerve reconstruction and adequate well-vascularized soft-tissue coverage. Vascularized nerve grafts are indicated for defects longer than 10 cm. The authors described a new technique combining a free vascularized sural nerve graft (Doi 1984) with a fasciocutaneous posterior calf flap (Walton) proximally based on the superficial sural artery.

An anatomic study on 26 cadaver legs (Thiel-fixated and silicone injected) was carried out. The flap design with its cutaneous expansion is centered in the midline of the proximal posterior calf. Dissection is started medially, including the posterior calf fascia overlying the gastrocnemius muscle, continues to the midline, including the sural nerve and superficial sural artery with its septocutaneous perforators. The preparation can be extended as far laterally as necessary, with the option of including the lateral cutaneous sural nerve. The vascular pedicle and the nerves are dissected to their origin in the poplitea.

Twenty-six flaps were dissected. In 13 cases, the medial sural artery was the nourishing vessel; in 12 instances, blood supply came from the popliteal artery directly, and once from the lateral sural artery. The average diameter of the pedicle artery was 2.4 mm (range: 1–4 mm) located, on average, 1.5 cm proximal to the popliteal crease. Pedicle length measured 4.5 cm on average. A comitant vein was present in 21 cases with an average diameter of 2 mm; in 5 cases, a separate deep or superficial vein was dissected.

The sural nerve was accompanied by the superfial sural artery, 18.6 cm on average. When the lateral cutaneous sural nerve was included, 35.3 cm of vascularized nerve could be gained. Adding the non-vascularized segments of both nerves, the total nerve length represented 57 cm on average.

One clinical case was presented, comparing the septocutaneous vascularized sural nerve free flap with a non-vascularized sural nerve graft for reconstruction of the median and ulnar nerves.

The ideal indication for this flap is a combined soft-tissue and nerve defect longer than 10 cm, requiring a thin, pliable coverage. It offers reliable blood supply with constant septocutaneous perforators, pedicle size, and two nerves. Flap donor-site morbidity is low, and loss of sensibility corresponds with conventional sural nerve grafting.