Reconstruction of lower limb defect with a variant sural neuro-fasciocutaneous flap: A case report

Abstract

Introduction: The sural neuro-fasciocutaneous flap is widely used for reconstructing skin defects in the lower calf. Variations of the sural nerve in the calf are infrequent, which may require a variation in the traditional surgical procedure.

Case presentation: A 76-year-old male patient had soft tissue defect of the right lateral ankle and lower leg caused by an accident 18 years ago. He had exposed bones and had osteomyelitis. He underwent two primary operations, and finally, we used a sural neuro-fasciocutaneous flap to effectively cover the defect. We observed that the course of the sural nerve was atypical during the surgery, and we adjusted the flap axis laterally to bring the lateral sural cutaneous nerve inside the flap to improve the success rate of the surgery. The flap entirely survived, and there was no sensory impairment in the calf. The patient was discharged from the hospital after 10 days.

Clinical discussion: Some type of variant of the sural nerve makes the flap harvest without the neurovascular component of the sural nerve and the cutaneous chain, which might decrease flap survival. Moving the flap axis laterally and bringing in the lateral sural nerve or peroneal communicating nerve offers an adequate blood supply to the vascular territory and the flap region.

Conclusion: In patients with sural nerve variants, the procedure does not have to follow the traditional theory of the sural neuro-fasciocutaneous flap. Preoperative and intraoperative protection of the sural nerve variant should also be considered.

Keywords: Case report; Lateral calf defect; Reconstruction; Sural neuro-fasciocutaneous flap; Variant.

Fig. 1

The patient's course of treatment. a: Preoperative view of the right lateral calf defect. b: Preoperative DR image of the right ankle (frontal view). c: Preoperative DR image of the right ankle(lateral view). d: Filling the defect with bone cement in the first-stage of surgery e: Preoperative markings for second-stage operation (lateral view). f: Preoperative markings for second-stage operation (posterior view). g: Intraoperative flap harvest and coverage. Black arrow: sural nerve penetrating into the muscle. h: intraoperative dissection of the medial sural cutaneous nerve. Black arrow: raised sural nerve, not penetrated from the Achilles tendon i: Immediate postoperative result. The donor site was closed by grafting excess “dog ear” skin from the upper calf. j: The postoperative result was cosmetically and functionally acceptable. k: Appearance at 6 months postoperatively.

Fig. 2

Intraoperative adjustment of the flap axis. A: The conventional preoperative marking of the procedure. B: The actual intraoperative marking of the procedure. The axis was displaced laterally to bring the lateral sural cutaneous nerve into the flap. Yellow dashed line: normal sural nerve route and flap design axis; Red dashed line: pedicle area of the flap; Blue triangle: the ineffective donor site of the flap; Red star: Point of insertion of the lateral sural cutaneous nerve into muscle. LHGM - lateral head of gastrocnemius muscle; MHGM - medial head of gastrocnemius muscle; AT - Achilles tendon; PLM - peroneus longus muscle; SN - sural nerve; MSCN - medial sural cutaneous nerve; LSCN - lateral sural cutaneous nerve.

Fig. 3

Classification of sural nerve variations. SCN - sciatic nerve; TN - tibial nerve; CPN - common peroneal nerve; SN - sural nerve; MSCN - medial sural cutaneous nerve; LSCN - lateral sural cutaneous nerve; PCN - peroneal communicating nerve; LDCN - lateral dorsal cutaneous nerve.