Can Great Toe Pedicle Flaps Have An Impact For Complicated DFUs?

Diabetic ulcers, particularly those located in the forefoot region, pose an interesting challenge for the foot surgeon. When these ulcers occur in the neuropathic patient with adequate circulation, the pedicle flap of the great toe can serve as a useful tool for ulcer management.

   Frequently, ulcerations located on the plantar aspect can be difficult to treat because of their late clinical presentation. The presentation often involves large skin and soft tissue defects, extension to bone and insufficient local tissue for closure. Often, local simple treatment options have failed.

   Full thickness soft tissue defects can lead to exposure of deep structures including the flexor tendon, plantar plate or the metatarsophalangeal joint (MPJ). When left exposed for a period of time, these structures can become desiccated or infected. Often, the wounds have not responded to a trial of offloading or have healed with an unstable scar and are now subject to recurrent ulceration due to being on a weightbearing surface. For that reason, plantar wounds that have received split thickness skin grafts have the tendency to break down.

   Therefore, reconstructive options for midfoot and forefoot ulcerations should be reliable in terms of withstanding weightbearing forces. Since further delay results in worsening of the ulcer, the use of the pedicle flap of the great toe has become an interest over the last few years for soft tissue coverage of diabetic ulcerations of the forefoot.

Key Advantages Of The Great Toe Pedicle Flap

The use of the great toe pedicle flap has several advantages. The primary advantages include tissue based on a known and reliable vascular supply, increased mobility as opposed to a local flap, and avoidance of microvascular anastomosis.1

   Given that the flap is based on a known vascular supply, there are a couple of flap design options. It can be a peninsular axial or island-based flap. A peninsular axial flap is one in which the skin covers the pedicle. An island flap affords greater mobility because its pedicle solely consists of the supplying blood vessels. One can use this surgical procedure for smaller defects of the sole, generally defects that are 3.5 cm in diameter or smaller.

   Another consideration with flap procedures is donor site morbidity. With the great toe pedicle flap, the donor defect is from a non-weightbearing surface, which does not significantly alter the structure or function of the foot. The donor tissue is more durable, which is beneficial for plantar defects. Since the sole typically consists of sensate glabrous skin with fibro-fatty subcutaneous padding, the selected procedure, when healed, should withstand the plantar and shear pressures associated with weightbearing.

   Another advantage is the increased mobility of these flaps due to their defined circulation, which can be based upon the dorsal, plantar or both neurovascular bundles. As a result, they can be proximally or distally based.

   Contraindications to performing the great toe pedicle flap include vascular insufficiency, infection, poor quality skin, edema and non-adherence.

Emphasizing The Importance Of Preoperative Vascular Assessment

Due to variation in vascularity, appropriate preoperative vascular assessment with Doppler examination is crucial. In a pedicle flap, blood supply moves through an intact base or stalk. In preparation for selecting a graft, one should perform mapping of the digital arteries to the great toe with a handheld Doppler.

   The anatomy of the dorsal and plantar circulation varies from patient to patient.2 Typically, the anatomy of the great toe consists of the first digital metatarsal artery from the dorsalis pedis artery or the plantar digital artery via the lateral plantar artery. Communicating branches from the dorsal and plantar system are by way of the pedal arch. The dorsalis pedis becomes the first interosseous artery and divides into the first and second metatarsal to communicate with the lateral plantar artery. The digital arteries can be less than 1 mm thick and visualization best occurs with loupe magnification.

   Typically, the pivot point is at the common digital artery. However, in cases in which additional length is needed, one can trace the digital artery of the first web space to the dorsalis pedis artery after the first dorsal interosseous muscle divides to permit visualization. When arterial inflow is antegrade or one is planning to utilize the great toe pedicle flap as a free flap, the surgeon can further dissect the pedicle to the anterior tibial artery. Further discussion of the free flap is beyond the scope of this article.

   The blood supply to the great toe depends on the arterial anastomosis of the medial plantar artery, lateral plantar artery or first dorsal metatarsal artery. If all of these vessels are patent, then all three supply flow to the great toe.

   Occasionally, increased mobility is required for coverage of distal forefoot defects. One should also assess retrograde flow to the great toe. If one places the Doppler over the lateral plantar artery with occlusion of the dorsalis pedis artery and the signal is audible, this signifies antegrade flow from the posterior tibial artery to the lateral plantar artery.3 An inaudible signal at the lateral plantar artery represents retrograde flow from the dorsalis pedis artery. However, this flap variation is contraindicated when the plantar circulation is absent.

   Detailed angiography can occur as part of the preoperative workup for flap design if the clinical scenario warrants further investigation. Multiple views of the foot are helpful for visualizing digital arteries, the presence or absence of dorsal-plantar communication, or any vascular anomalies. The dorsal venous network supplies an abundance of vascular choices for outflow.

Pertinent Considerations With Flap Design

One must thoroughly investigate both the recipient and donor sites. If infection is present, appropriate treatment is a major component that contributes to flap survivability. Antibiotic therapy can control bacterial load. Surgical debridement is necessary to remove any non-viable or infected tissue. Surgeons should properly prepare the wound and delay soft tissue reconstruction until all signs of inflammation and infection have resolved. When excising the plantar ulceration, the surgeon should do so with caution so as not to injure the metatarsal artery and its digital branch to the side of the toe donating the flap.

   Some considerations in flap design include the size of the donor defect, the depth of the recipient defect and the amount of mobility required to achieve closure. This includes examining the size and depth of the recipient site along with the type of exposed tissue (subcutaneous tissue, muscle, tendon, capsule or bone). If deep structures are exposed, then the recipient wound base may require some granulation tissue formation. The condition and characteristics of the donor site are equally as important. The donor skin and tissue must be healthy to ensure flap take.

   The lateral hallux is the first choice of donor site since it has a larger flap area and digital vessels. Other typical donor sites include the other digits. The next commonly utilized site besides the great toe is the second toe. The depth of tissue involvement can include fasciocutaneous or osteocutaneous tissue. The clinical indication for harvesting bone is an osseous defect or exposed joint. Vascularized bone graft is helpful for wound closure of deep defects or when performing an arthrodesis in complex or revisional cases.

   The clinical indication for harvesting bone is usually when there is an osseous defect or exposed joint in which vascularized bone is helpful for wound closure of deep defects or arthrodesis.

   Close the donor site primarily by skin graft, local flap or syndactylization of toes. The flap can be based on the dorsal or plantar circulation. Advantages to the flap based from the plantar arterial network include potentially less functional abnormality since the dissection does not require transection of the deep transverse metatarsal ligament. Typically, this ligament supports the metatarsals in the transverse plane.

   A pedicle flap is limited by the arc of rotation so one must carefully measure the location of the donor site in relation to the recipient site. Too much tension or stretch on the pedicle flap can lead to flap failure. Measuring and tracing the ulceration with a paper template can allow one to outline the flap dimensions on the donor toe. The nail and nail bed are not included. It is helpful to perform an intraoperative Doppler exam of the digital artery. One surgical pearl to prevent injury to the digital vessels during dissection is to include a layer of protective padding and preserve the fat pad or subcutaneous tissue encasing the neurovascular bundle.

   One can close the donor site primarily by skin graft, local flap or by syndactylization of toes. If necessary, the surgeon can achieve tissue laxity by undermining the tissue at the recipient site, which then permits for secondary motion.

A Guide To Postoperative Care

A non-adherent dressing covers the wound. For the graft to successfully take, the amount of apposition to the recipient site is important.

   The more apposition the great toe pedicle flap has, the higher the chances of graft survival. Carefully secure the flaps down to the recipient site. Ensure adequate hemostasis prior to securing the flap. The use of drains can prevent hematoma and seroma formation, both of which can contribute to graft failure. Elevation of the lower extremity reduces fluid collection and edema, which may impair healing.

   Consider general offloading principles to protect the site from pressure and shear forces. This can be in the form of splinting and immobilization. Immobilizing the affected area to prevent these forces for four to six weeks is typical.

   After grafting, resume proper wound care and infection control to ensure flap survival. An infected wound or flap can lead to necrosis and ultimately failure of flap take.

   Currently, evaluation of flap perfusion relies on close postoperative physical examination. Clinical signs to watch out for include skin color, temperature, turgor and capillary refill time. The use of an arterial Doppler can assess direct flow to the flap over a specific region. One can investigate the patency of the vascular supply or whether there is thrombosis of the digital artery supplying the flap.

In Summary

A successful pedicle flap requires comprehensive pre- and postoperative care, proper patient selection, a strong understanding of anatomy, and recognition and management of complications. Plastic surgery techniques like the great toe fillet flap are an effective tool for podiatric surgeons for coverage of tissue defects.

   Dr. Shum is a third-year resident with the Cedars Sinai Medical Center Podiatric Medicine and Surgery Residency Program in Los Angeles.

   Dr. Belczyk is a Fellow of the American College of Foot and Ankle Surgeons, and is board certified in both foot surgery and reconstructive rearfoot/ankle surgery by the American Board of Podiatric Surgery. He is a consultant physician at the Amputation Prevention Center at Valley Presbyterian Hospital in Van Nuys, Calif.

   Dr. Rogers is the Associate Medical Director of the Amputation Prevention Center at Valley Presbyterian Hospital in Los Angeles. He is the Chair of the Foot Care Council for the American Diabetes Association. Dr. Rogers has more than 50 publications in press or in print on diabetic foot disorders including several book chapters.

   Dr. Andros is the Medical Director of the Amputation Prevention Center at Valley Presbyterian Hospital in Los Angeles. He is a board-certified vascular surgeon with over 40 years experience and is a renowned specialist in the revascularization of diabetic limbs. Dr. Andros serves as the Co-Director of the Diabetic Foot Global Conference and is a member of the American Diabetes Association and the Society for Vascular Surgery.

   Dr. Lee is a consultant physician at the Amputation Prevention Center at Valley Presbyterian Hospital in Van Nuys, Calif. She is board certified in general and vascular surgery.

References
1. Granick MS, Newton ED, Futrell JW, Hurwitz D. The plantar digital web space island flap for reconstruction of the distal sole. Ann Plast Surg. 1987; 19(1): 68-74.
2. Kelikia AS and Sarrafian, S. Sarrafian’s Anatomy of the Foot and Ankle: Descriptive, Topographic, Functional. Lippincott Williams & Wilkins, Philadelphia, third edition, 2011, p. 342.
3. Attinger CE, Evans KK, Bulan E, Blume P, and Cooper P. Angiosomes of the foot and ankle and clinical implications for limb salvage: reconstruction, incisions, and revascularization. Plast Reconstr Surg. 2006; 117(7Supp):261S-293S.

   Editor’s note: For further reading, see “Plantar Skin Flaps On Diabetic Ulcers: Are They Worth It?” in the March 2004 issue of Podiatry Today or “Pertinent Insights On Plastic Surgery And The Diabetic Foot” in the March 2011 issue.