Utility of Proximally Based Sural Fasciocutaneous Flap for Knee and Proximal Lower Leg Defects

The proximally based sural fasciocutaneous flap is an ideal alternative for reconstruction of soft tissue defects around the knee and on the proximal half of the lower leg. Its advantages include a thin sensate flap, good aesthetic outcomes, and reduced donor site morbidity. However, there have been limited reports regarding its clinical application. This study presents the use of the proximally based sural fasciocutaneous flap in 18 cases. Materials and Methods. The series consisted of 18 cases (10 males) with an average age of 38.6 years and with a median follow-up time of 16 months. The defects were located around the knee in 3 cases and on the proximal half of the lower leg in 15 cases. The pivot point was between 1.5 cm and 2 cm distal to the popliteal skin crease and the fasciocutaneous pedicle was between 3 cm and 4 cm wide. The flap size ranged from 8 cm² x 7 cm² to 16 cm² x 12 cm², and the pedicle length ranged from 12 cm to 18 cm. The anatomical structures consisted of the superficial and deep fascia, the sural nerve, lesser saphenous vein, and superficial sural artery with an islet of subcutaneous cellular tissue and skin. Results. All 18 flaps survived. No arterial and venous crisis occurred postoperatively in any case. All donor sites had one-stage closure with split-thickness skin grafts and all the grafted skin survived without further surgical treatment. Functional deficits were not detected in any of these cases. Conclusion. The proximally based sural fasciocutaneous island flap is reliable and suitable for reconstruction of soft tissue defects around the knee and on the proximal half of the lower leg with more versatility.

  Soft-tissue defects around the knee and on the proximal lower leg are common due to trauma and postoncologic excision.¹ There are various options available for reconstruction of such defects, usually including local muscle flap, fasciocutaneous flap, free flap, and cross-leg flap.^2-4 Generally, a local muscle flap yields a bulky appearance and muscular function is damaged; a free flap requires excellent microsurgical technique, which limits its wide application in the authors’ clinic; and a cross-leg flap inevitably brings about severe discomfort. While an island fasciocutaneous flap based on located perforator or fascial feeder vessels provides satisfactory coverage, as well as satisfactory cosmetic and functional outcomes,^5,6 there have been limited clinical reports regarding proximally based sural fasciocutaneous island flaps for such reconstructions.^1,3,7

  This study evaluates the clinical outcomes of using a proximally based sural fasciocutaneous island flap for reconstruction of traumatic soft-tissue defects around the knee and on the proximal lower leg.

  Between December 2009 and December 2012, 18 patients (10 males) at the Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology (Wuhan, China) underwent surgery for soft-tissue defect reconstruction using a proximally based sural fasciocutaneous flap. All patients gave written, informed consent, and the study was approved by the ethical committee of the hospital. All surgeries were performed by the corresponding author. The average age of the patients at the time of surgery was 38.6 years, and the median follow-up time was 16 months (range: 4-24 months). Defects were located around the knee in 3 cases and on the proximal half of the lower leg in 15 cases. Road traffic accident was the cause of the soft-tissue defects, including acute soft-tissue necrosis in 12 cases and postoperative internal hardware exposure in 6 cases. Associated risk factors were diabetes, advanced age, cigarette smoking, and high blood pressure. The flap size ranged from 8 x 7 cm² to 16 x 12 cm² and the pedicle length ranged from 12 cm to 18 cm (Table 1).

  Surgical Technique. Patients were positioned prone or lateral and a tourniquet was placed in the proximal thigh and pressurized without exsanguination. The venous congestion could facilitate the identification and dissection of the neurovascular structures. A radical debridement of the recipient region should be performed before flap transplantation.

  Anatomically, the proximally based sural fasciocutaneous island flap consisted of an islet of skin and subcutaneous fat, the superficial and deep fascia, sural nerve, lesser saphenous vein, and the superficial sural artery. The flap circulation mainly depended on the median superficial sural artery, which mostly originated from the popliteal artery.

  Initially, a line was drawn on the posterior calf to indicate the course of the sural nerve and adjacent lesser saphenous vein, usually extending from the midpoint of the lateral malleolar tip and Achilles’s tendon to the midpoint of the popliteal skin crease. The donor site was centered on this line, which also roughly marked the course of the pedicle. The pivot point of the pedicle was usually set on the line 1.5 cm to 2 cm distal to the popliteal skin crease, where it was about 1.5 cm away from its origin of the sural artery. A skin islet was drawn by 15% enlargement of the dimension of defects in the form of a paddle, with 2 cm increment of pedicle length and with about 3 cm pedicle width (Figure 1).

  Thereafter, the entire flap was dissected and elevated from distal to proximal. Initially, the skin and subcutaneous fascia were dissected distally to incorporate the deep fascia, the ligated lesser saphenous vein, and the sural nerve together. The lesser saphenous vein is always superficial, but the sural nerve penetrates the deep fascia at the midpoint of the lower leg and then follows a course between the 2 heads of the gastrocnemius muscle. The proximal neurovascular structures should be always carefully dissected so as not to damage them, especially the proximal sural nerve. Sometimes, the central axis of the flap and its pedicle were adjusted so as to include the sural nerve, the lesser saphenous vein, and the nearby sural artery when any of the neurovascular structures significantly diverged from the course line. Interrupted suture between the skin and the subcutaneous deep fascia was required to prevent sliding of both layers. Finally, the entire flap was elevated between the deep fascia and the aponeurosis of Achilles’s tendon or gastrocnemius muscular fascia on the posterior calf until reaching the pivot point.

  A blunt dissection near the pivot point should be carefully performed so as not to damage the incorporated median sural artery. Once the flap was entirely evaluated, the tourniquet was deflated and the flap circulation was checked. Occasionally, a hot pack with warm normal saline was used to relieve spasm of the vessels incorporated in the pedicle. After verifying good circulation of the flap, an open tunnel was incised and, through the tunnel, the flap and its pedicle were transposed laterally or medially to the recipient defects by careful rotation over the pivot point, avoiding both torsion and tension. After attachment to the recipient defects, the flap was sutured with no tension. 

  The donor sites were all closed in one stage with split-thickness skin graft. The vacuum sealing drainage technique was routinely used to achieve effective compression to the grafted skins. The drainage strips were put around the flap and its pedicle to allow bleeding. Generally, external supports were not used due to possible compression to the flap, however, patients were not permitted to vigorously move their knee joints during the first 5-7 days following surgery. The drainage strips were taken away 48 hours postoperatively and the vacuum sealing drainage dressing was removed 7-10 days postoperatively.

  Case 1. A 34-year-old man was involved in a traffic accident and sustained closed tibial medial and lateral plateau fractures (Figure 2). One week after the injury, he underwent an open reduction and internal fixation surgery. Skin and soft-tissue necrosis around the incision occurred postoperatively and the internal hardware was exposed in the upper tibia. A radical debridement was initially performed and, as a result, a 12 cm x 7 cm soft-tissue defect occurred in the proximal tibial anterior-medial facet. A proximally based sural fasciocutaneous flap (14 cm x 8 cm in size and 16 cm pedicle length) was performed to reconstruct such defects. The donor site was closed with split-thickness skin graft. The flap and the grafted skin survived without any complications, and at about 3 weeks postoperation the defects healed completely. At the last follow-up, 24 months postoperation, the patient was satisfied with the clinical outcomes.

  Case 2. A 48-year-old woman with diabetes and high blood pressure was involved in a road traffic accident, resulting in severely bruised skin on the proximal lower leg (Figure 3). A huge absess formed locally and, subsequently, necrosis of the involved skin and subcutaneous soft-tissue occurred. Initially, radical debridement was performed and resulted in an 18 cm x 13 cm soft-tissue defect, including a 7 cm x 8 cm exposure of the proximal tibial anteromedial facet. A 15 cm x 9 cm proximally based sural fasciocutaneous flap was designed. The flap was laterally transferred to cover the exposed bone and the remaining defects were closed with split-thickness skin grafts. The donor site was closed in one stage with split-thickness skin graft. The defects healed without complications about 3 weeks postoperation. At the last follow-up, 24 months postoperation, the patient was very satisfied with her clinical outcomes.

  In this series, the size of soft-tissue defects ranged from 6 cm² x 6 cm² to 18 cm² x 13 cm² and the size of island skin flaps ranged from 8 cm² x 7 cm² to 16 cm² x 12cm². The pivot point was 1.5 cm - 2 cm distal to the popliteal skin crease and the pedicle length ranged from 12 cm to 18 cm. The lowermost border of the flap reached the distal fourth of the lower leg. The mean operation time was 80 minutes, with a range from 60-110 minutes.

  All the donor sites were closed in one stage with split-thickness skin graft. There were no arterial or venous crises postoperatively in any cases. All 18 flaps survived and yielded satisfactory coverage. No morbidity of the donor site or functional deficits of the knee and ankle were detected, and no infection and tip or marginal necrosis was observed in any of the cases. None of the patients required additional surgical treatments. In all cases, the sensory loss of the dorsolateral aspect of the foot inevitably occurred; however, this was well tolerated by the patients. All patients were satisfied with both the aesthetic appearance and functional outcomes of the flaps at the last follow-up visit (median follow-up time 16 months). The presence of risk factors, such as diabetes, high blood pressure, advanced age, and cigarette smoking, seemed not to adversely affect the final clinical outcomes.

  Reconstruction of knee and proximal lower leg soft-tissue defects is a challenging operation. There are several methods available including local muscle flap, perforator-based flap, free flap, cross-leg flap, and axial pattern fasciocutaneous flap. The results of the local muscle/musculocutaneous flaps usually yield unsatisfactory cosmetic effects, appearing bulky, fatty, and disfigured, as well as damaging the normal muscular function. Both the perforator-based propeller flap and free flap procedures are associated with microsurgical technique difficulties.^8,9 The cross-leg flap brings inevitable discomfort since the contralateral healthy leg must be fixed together with the injured leg for approximately 3 weeks, requiring a 2-stage pedicle division and prolonged immobilization. Therefore, these methods are not always satisfactory.

  The proximally based sural fasciocutaneous island flap displayed some advantages for reconstructing soft-tissue defects of the knee and lower leg, due to the thin, pliable, long arc of rotation and functional and aesthetic superiority of this technique over other available flaps.³ In the authors’ experience, this proximally based fasciocutaneous flap had excellent reach, covering around the knee joint and on to the proximal half of the lower leg with a flexible and long, rotated pedicle. There was no morbidity of donor sites and only minimal damage to the limb. In addition, this technique provided an excellent aesthetic appearance with a thin and sensate flap, and there was little restriction on the movement of the involved knee joint.

  Anatomically, the flap and its pedicle consisted of the superficial and deep fascia, the sural nerve, short saphenous vein, and superficial sural artery together with an islet of subcutaneous cellular tissue and skin. The blood circulation of the flap mainly depended on the constant median superficial sural artery, which usually originates from the popliteal artery. The median superficial sural artery crosses the popliteal fossa and travels between the heads of the gastrocnemius muscle. It pierces the deep fascia somewhere in the upper two-thirds of the lower leg. After piercing the fascia, the median superficial sural artery travels just medial to the lesser saphenous vein toward the lateral malleolus.¹⁰ The artery courses alongside the sural nerve to the distal one-third of the leg, either terminating or anastomosing with the supramalleolar branch of the peroneal artery and posterior tibial artery. The musculocutaneous perforators from the gastrocnemius muscle provide a second source of anterograde blood flow that may provide equal or greater blood flow to the skin and fascia of the sural angiosome.¹¹ Based on constant anterograde flow irrigation, although much less common than distally based sural fasciocutaneous island flap, the proximally based sural fasciocutaneous flap is the preferred operative alternative for reconstruction of soft-tissue defects of the knee and lower leg defects.

  In 1985, Moscona et al¹² first described an islanded fasciocutaneous flap of the posterior calf for knee defect reconstruction as a random pattern flap deriving blood supply from the fascial plexus, and failed to recognize the contribution of the median superficial sural artery.¹² Following that report by Moscona and colleagues, the proximal posterior calf region was mainly developed to make free flaps based on the superficial median, medial, or lateral sural artery^5,13-15 and there have been few reports regarding the local pedicled fasciocutaneous flap for reconstruction of the knee and proximal lower leg.

  Satoh et al¹⁶ used posterior calf skin in the form of a sural fasiocutaneous flap in 17 clinical cases as pedicled, island, and free flaps. They concluded that the island sural fasiocutaneous flap was particularly versatile for the reconstruction of the soft-tissue defect around the knee joint. Cariou et al¹⁷ proposed an elaborate posterolateral sural fasciocutaneous island flap with proximal aponeurotic or adipofascial pedicle in 9 patients and found that the skin cover of the knee was considered to be of excellent quality, stable, and sensitive. Furthermore, Suri et al¹ and Cheon et al³ used the proximally based sural fasciocutaneous or adipofascial flap to repair the soft tissue defects in 10 and 37 cases, respectively, and there were no complete failures in their series except for minor tip necrosis, grafted skin necrosis, and superficial infection. They concluded the proximally based sural artery flap was reliable for soft tissue reconstruction around the knee and on the proximal lower leg. In the current study, the authors also harvested proximally based sural fasciocutaneous island flaps for soft-tissue reconstruction around the knee and on the proximal lower leg. The final clinical outcomes were satisfactory and encouraging due to good appearance, clinical function, and only minor complications. These results were similar or superior to that of the distally based sural flaps in the literature.^1,3,16,17 The accompanying arteries of the lesser saphenous vein were considered an additional source of cutaneous branches to the posterior skin of the leg.^18,19 It was beneficial to the flap circulation to keep the lesser saphenous vein intact. Because the lesser saphenous vein always has a suprafascial course along the entire leg, it was very easy to identify through the loose fascia when elevating the flap. The authors always kept the actual course of the lesser saphenous vein as the central axis of the flap and its pedicle, despite the previously drawn axis. Accordingly, the medial and lateral borderlines of the flap were changed. The lesser saphenous vein, sural nerve and the superficial sural artery were always included in the flap and its pedicle. The authors believe this procedure helps preserve blood supply of the flap, which is critical for the circulation of the pedicled flaps, and greatly affected their survival in this series. All the cases in this study were related to acute traumatic injury;however, soft-tissue defects of the knee and proximal lower leg due to chronic infection, postoncologic excision, and total knee arthroplasty are not uncommon. The proximally based pedicled flap may also be a good choice for reconstruction of these defects. The disadvantages of this proximally based sural fasciocutaneous island flap include sensory loss in the dorsolateral aspect of the foot, and the scarring of grafted skins in the donor site yielding inferior cosmetic appearance. In the authors’ experience, these problems were considered minor and were well tolerated by patients.

  This proximally based sural fasciocutaneous island flap was reliable and efficient to reconstruct soft-tissue defects around the knee and on the proximal lower leg with more versatility than other flap techniques the author has used. The procedure is relatively easy to learn and this flap is an ideal alternative coverage for soft-tissue defects such as those described in this study.

The authors are from the Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Address correspondence to:
Haitao Pan, MD, PhD
Department of Orthopaedics
Union Hospital
Tongji Medical College
Huazhong University of Science and Technology
Wuhan 430022, China
panhaitao2000@gmail.com

Disclosure: The authors disclose no financial or other conflicts of interest.