A Guide To Closure Techniques For Open Wounds
The soft tissue envelope of the foot resists severe mechanical stresses on a daily basis and protects the underlying structures from injury. However, an injury to the foot or a chronic ulcer can cause a defect in the soft tissues and presents a daunting challenge for the foot and ankle specialist. When the defect is on the sole of the foot, the injury may be disastrous. Historically, soft tissue lesions have been treated conservatively via various techniques of offloading, local wound care, molded shoes, inserts and orthoses. While some wounds lend themselves well to non-operative treatment, there are many wounds that either refuse to close or close with a resultant scar that is so unstable that recurrence of the ulcer is all but assured. Since the 1980s, there has been an emerging body of literature reporting on outcomes from reconstruction of the soft tissues of the foot. Historically, these procedures were the domain of the plastic surgeon, but as the training of foot and ankle surgeons has increased in duration and scope, these procedures are now being taught in a podiatric surgical fellowship. The ability of a surgeon to close a wound, which has been open for months and sometimes years, gives new hope to many patients and their families, whose lives revolve around the long-term treatment of these wounds. The majority of foot and ankle wounds are seen in the diabetic population, and many of the comorbidities associated with diabetes (such as peripheral vascular disease, Charcot neuroarthropathy and the loss of protective threshold) make it quite challenging to close wounds in these individuals. Since many of the ulcers are linked to acquired deformities associated with Charcot neuroarthropathy, one must integrate soft tissue reconstruction and the management of Charcot deformities into any treatment plan. Competency in using multiplanar external fixators is essential in treating these complex patients. How Do Skin Grafts Facilitate Closure? Soft tissue reconstruction of the foot and ankle includes the use of skin grafts, local flaps and pedicle flaps. The use of free flaps, once essential in the treatment of defects of the hindfoot and ankle, has waned with the advent of reverse flow neurocutaneous flaps harvested from the lower leg. Let’s begin by taking a closer look at skin grafts. Skin grafting provides fast and easy coverage of wounds. Split thickness skin grafts are harvested tangentially and include the epidermis and, depending on the thickness, elements of the dermis. You would use a power instrument called a dermatome to harvest the graft. Postoperatively, you would cover the donor site with Vaseline impregnated gauze that is allowed to slough as epithelialization progresses beneath it. The graft’s survival is dependent on its rapid revascularization. Inosculation of skin grafts by vascular buds usually begins by the fifth postoperative day and proceeds until venous drainage of the graft has been established (usually by the second week). During the first 48 hours postoperatively, fibrin is laid down between the graft and the bed. Doing so helps anchor the graft to the donor site. The axiom is thin split thickness grafts “take” better than full thickness grafts because the thinness of the graft allows for easier imbibition and a more rapid inosculation. To prevent slough, you must ensure close adherence of the skin graft to the recipient site and protection from shear.1-3 When it comes to the diabetic foot, split thickness skin grafts are used frequently in nonweightbearing areas or to cover donor sites of locally raised flaps. However, one should avoid using skin grafts in areas that are subjected to significant stress. Also keep in mind that a split thickness skin graft will not prevent contraction of a wound. Full thickness skin grafts are harvested by excision and include the epidermis and dermis. Using full thickness grafts will prevent the wound from undergoing further contraction. Full thickness skin grafts are usually harvested from areas where there is a skin redundancy. These areas include the flexor surfaces of joints, such as the wrist, the sinus tarsi or the inguinal fold. One may also harvest full thickness skin grafts from the lateral thigh. When you take a full thickness skin graft, you should close the donor site primarily. Skin grafts will fail if there is active bleeding or transudation below the graft. This can lead to a hematoma or seroma and prevent adherence of the graft to the bed. You can apply full thickness skin grafts to muscle, fat or vascularized tendon sheath. Keep in mind that bare tendon and fascia, which are relatively avascular, will usually not be able to sustain the viability of a skin graft. As we noted earlier, you should ensure post-op protection of the skin graft from shear until the graft has been completely inosculated. Should You Consider Local Flaps? Local flaps are areas of tissue that are raised and mobilized to close wounds in immediately adjacent areas. These flaps are composed of tissues similar to those that were lost and provide durable coverage.4-6 Using these flaps with the resultant primary closure enables you to avoid the dysfunctional plantar scars that develop when one allows wounds to close secondarily.7 Local flaps are vascularized by random blood vessels and they include skin and subcutaneous tissue.8 You may use local flaps to cover bone, tendon and underlying connective tissue. Flaps are described by the nature of their movement from their donor sites to their recipient sites. These movements are advancement, transposition and rotation. Flap designs used on the sole have been borrowed from other anatomic areas of the body. The skin in those anatomic regions is more mobile than that of the sole of the foot, so applying these flaps to the foot is somewhat limited by the weightbearing soft tissue and its relative lack of mobility. In order to compensate for the lack of elasticity in the soft tissue of the sole, surgeons often resect bone for reasons of deformity or osteomyelitis. Doing so creates soft tissue laxity and permits flap movement that would otherwise be unavailable. A local flap’s viability is based on its ability to relocate without tension. The flap should be equal to or greater in durability and mobility than the original skin.9 If donor sites require split thickness skin grafting, you should limit them to the arch and other areas of low functional demand. There is an extensive subcutaneous neurovascular plexus on the sole. This is the result of collateralization between the maleollar and tarsal arteries with perforators from the medial and lateral plantar arteries. Therefore, one can safely raise flaps from a transverse position in the heel and midfoot.10 One can create plantar flaps via undermining in the suprafascial plane. When it comes to the extent of undermining of a flap, one should do enough to permit movement but avoid excessive dissection as this may jeopardize a flap’s viability. Be sure to preserve vessels that perforate the flap. The postoperative care of each local flap is extremely important and requires close observation. Remember, each diabetic patient who undergoes reconstruction will heal at his or her own pace so you should avoid premature suture removal. Key Pointers On Advancement, Rotation And Transposition Flaps Advancement flaps involve the linear movement of skin and subcutaneous tissue. These flaps are of great value in closing wounds on the forefoot. The blood supply to the skin in this region is derived from a series of perforators, so one can create islands of skin and subcutaneous tissue and move them in any direction within the limits of the perforating vessels. A careful release of the mooring ligaments and preservation of the vascular pedicles will permit surface movement of up to 1.5 cm in any direction. For larger defects, one may design two flaps of similar dimensions and advance them toward each other. These flaps are designed so their trailing edge is a teardrop shape. This facilitates the closing of the donor site primarily in a V to Y fashion. One may use rotation flaps to close midfoot wounds, especially those associated with a Charcot deformity. Rotation flaps can be subfascial or suprafascial. One can elevate them from the nonweightbearing arch and rotate them to the heel.11 Be aware that rotation flaps’ donor sites usually do not require coverage with a skin graft. These flaps allow for broad exposure to the underlying bone and provide easy access for ostectomy of fusion within the midfoot. Primary closure of a rotation flap usually results in a “dog ear,” which one can resolve by performing a triangular excision. Transposition flaps are similar to rotation flaps except these flaps are tongue-like in shape and generally have narrower bases than rotation flaps. The surface area of a transposition flap is less than the surface area of a rotation flap covering a defect of the same size. Transposition flaps are also more likely than rotation flaps to require split thickness skin grafts to close their donor sites, especially in the plantar arch. Transposition flaps are more capable than rotation flaps of covering larger wounds in the plantar hindfoot because the coverage of the donor site by a split thickness skin graft augments the total surface area. A number of modifications to the standard transposition flap have been described and many have been utilized in the foot. These modifications include rhomboid flaps, bilobed flaps and Z plasties. Why Pedicle Flaps Are Advantageous Unlike local random flaps, pedicle flaps are defined as areas of tissue that have an identifiable neurovascular supply. These flaps may be in the form of an island, in which the skin is circumscribed, or a peninsula, in which the skin is continuous with the surrounding tissue. The development of these flaps, which are based on a specific neurovascular axis or stalk, has greatly improved the reconstructive surgeon’s ability to repair defects in the foot. Most of the pedicle flaps used in foot and ankle surgery have the advantage of being harvested from non-weightbearing tissue so failure of one of these flaps does not create a larger defect on the plantar surface of the foot. Pedicle flaps may be fasciocutaneous, adipofascial or muscular in nature. Because the foot and lower leg have a rich collateral network of vessels, pedicle flaps may be developed with an antegrade (anatomic) blood flow or with a retrograde flow. Retrograde flow occurs when the normal flow in both the arteries and veins are reversed, due to a pressure gradient created by collateral vessels. This allows one to develop a flap from a proximal donor site on the foot or lower leg and move it to a more distal location. What You Should Know About Other Types Of Flaps Digital artery island flaps. Replacing soft tissue defects on the hand with neurocutaneous islands taken from the sides of the fingers has been described by Littler, Atasoy and others.12-16 The successes from these operations eventually led to similar flaps being developed to cover defects on the foot.17-18 Surgeons commonly use the lateral surface of the great toe and the medial surface of the fifth toe for these flaps because the metatarsal arteries, which give rise to their digital arteries, are inherently the longest and provide the easiest dissection and a greater arc of rotation.19 Flaps taken from the sides of the toes can be used to resurface the forefoot primarily. Once these adipofascial flaps are inset, they move with the surrounding tissue, thereby avoiding strain at the interface of the flap and the surrounding tissue. Instep flaps (medial plantar artery flaps). Flaps raised from the instep are supplied by the collateral flow of the dorsalis pedis and cutaneous perforators from the medial plantar artery. In the absence of an intact medial plantar artery, one may raise this flap as a medially based peninsula, making such a flap a random transposition or rotation flap. If there is a patent medial plantar artery, the surgeon may raise these flaps with either antegrade or retrograde flow. If the flaps are distally-based (retrograde), they can be used to resurface the forefoot while a proximally-based pedicle will allow for proximal rotation to close defects of the heel.20-23Reverse flow sural artery neurofasciocutaneous flaps. These flaps are useful in covering defects on the lower leg and heel, areas which had previously required free muscle flaps. One may raise islands of tissue from the posterolateral surface of the leg, based on the arteries that accompany the median branch of the sural nerve and the arterial commitantes of the lesser saphenous vein. These vessels anastomose with a series of septocutaneous perforators from the peroneal artery. This facilitates retrograde filling of the flap.24-27 One may close the donor site primarily or with a skin graft, depending on the size of the flap. Muscle flaps. Muscles have been used to provide bulk to a defect. They can also provide well-vascularized coverage to exposed bone. Type II muscles that have a major pedicle on which the flap is based, and several minor ones, are used for this purpose.28-29 After mobilization of the muscle, one can inset it into the defect and cover it with a split thickness skin graft. In the foot, the abductor hallucis, the abductor digiti minimi and the flexor digitorum brevis are commonly used to cover defects of the medial heel, the lateral heel, and the plantar heel and midfoot respectively. One may raise the extensor digitorum brevis on the lateral tarsal artery and use it to cover defects on the dorsum of the foot. Why Thorough Debridement Is Essential Chronic wounds contain necrotic tissue, fibrin, colonized bacteria and byproducts of tissue metabolism, all of which conspire to prevent wound healing. Before making any attempt at wound reconstruction, a thorough debridement is required to convert a chronic wound into a clean acute one. One must sharply remove all non-viable tissue and this will often make a large wound even larger. It is not uncommon for a patient to be brought back to the operating room several times for debridements before you determine that the wound is ready for closure. Failure to convert a wound into a clean wound essentially guarantees failure of any subsequent reconstruction. In Conclusion Protocols are changing for the treatment of chronic wounds of the foot and ankle. While offloading and local wound care remain valuable adjuncts, they are being replaced by soft tissue reconstruction. The foot and ankle surgeon’s role in this area has grown as the treatment paradigm has shifted. Dr. Jolly is the Chief of Podiatric Surgery and is the Director of the PGY-4 Fellowship in Reconstructive Foot and Ankle Surgery at New Britain General Hospital in New Britain, Conn. He is also a Clinical Professor of Surgery at the Des Moines University School of Podiatric Medicine and Surgery, and is the President-Elect of the American College of Foot and Ankle Surgeons. Dr. Blume is Clinical Assistant Professor in the Department of Orthopaedics and Rehabilitation at the Yale School of Medicine. He is also a Fellow of the American College of Foot and Ankle Surgeons and is the Director of Limb Preservation at the Yale New Haven Hospital in New Haven, Conn. Dr. Zgonis is a Fellow in Reconstructive Foot and Ankle Surgery at the New Britain General Hospital in New Britain, Conn. He is also a PostDoctoral Research Fellow within the Department of Orthopaedics and Rehabilitation at the Yale School of Medicine in New Haven, Conn.
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