Lower Extremity Microsurgical Reconstruction

CME Lower Extremity Microsurgical Reconstruction Lior Heller, M.D., and L. Scott Levin, M.D. Durham, N.C. Learning Objectives: After studying this article, the participant should be able to: 1. Understand the indications for the use of free-tissue transfer in lower extremity reconstruction. 2. Understand modalities to enhance the healing and care of soft tissue and bone before free-tissue transfer. 3. Understand the lower extremity reconstructive ladder and the place of free-tissue transfer on the ladder. 4. Understand the specific principles of leg, foot, and ankle reconstruction. 5. Understand the factors that influence the decision to perform an immediate versus a delayed reconstruction. Free-tissue transfer using microsurgical techniques is now routine for the salvage of traumatized lower extremities. Indications for microvascular tissue transplantation for lower extremity reconstruction include high-energy injuries, most middle and distal-third tibial wounds, radiation wounds, osteomyelitis, nonunions, and tumor reconstruction. The authors discuss the techniques and indications for lower extremity reconstruction. (Plast. Reconstr. Surg. 108: 1029, 2001.) Microsurgery for extremity reconstruction began more than three decades ago with the introduction of the operating microscope for anastomosis of blood vessels, as described by Jacobson and Suarez. 1 Microsurgical repair of digital arteries and digital replantation began in the 1960s, 2,3 and microsurgical composite tissue transplantation began in the 1970s. Microsurgeons expanded their efforts from achieving tissue survival to include the improvement of function and appearance in the 1980s. In the 1990s, the emphasis shifted to outcome by providing coverage and facilitating function. In the new millennium, free-tissue transfer using microsurgical techniques is now routine for the salvage of traumatized lower extremities. 4 6 Functional composite free flaps, such as the dorsalis pedis with extensor tendons, or innervated flaps, such as the innervated myocutaneous gracilis transplant, represent stateof-the-art reconstruction in which several reconstructive functions are performed in one procedure to achieve a functional limb. These advances, together with the possibility of prefabrication or pre-expansion of flaps, have enabled reconstruction surgeons to approach more challenging cases of reconstruction of the lower limb with resultant improved outcomes. The use of free-tissue transfer represents the highest rung on the reconstructive ladder, and it may be applied in combination with lower rungs on the ladder, such as skin closure, skin grafting, or rotational flaps (Fig. 1). Indications for microvascular tissue transplantation for lower extremity reconstruction include high-energy injuries, most middle and distal-third tibial wounds, radiation wounds, osteomyelitis, nonunions, and tumor reconstruction. SELECTION OF TISSUE TRANSPLANTATION The selection of the free flap for lower extremity reconstruction is based on several factors. Free flaps can be categorized into two different types of transplants. The first is the isolated transplant of tissue, such as muscle, skin, fascia, or bone. Usually a composite replacement is chosen; this is a more sophisticated flap. Composite flaps provide more than one function. Examples include myocutaneous, osteocutaneous, or innervated myocutaneous flaps. The type of tissue deficiency, its volume, and the wound surface area will determine the type of flap to be selected. Tissue transplants are selected with regard to do- From the Division of Plastic, Reconstructive, Maxillofacial, and Oral Surgery, Duke University Medical Center. Received for publication July 6, 2000; revised March 5, 2001. 1029

1030 PLASTIC AND RECONSTRUCTIVE SURGERY, September 15, 2001 FIG. 1. The reconstructive ladder. STSG, split-thickness skin graft; HBO, hyperbaric oxygen therapy; VAC, vacuum-assisted closure; 1, primary; 2, secondary. nor-site morbidity, recipient-site requirements, vascular pedicle length, and the anticipated aesthetic result. For example, a myocutaneous latissimus dorsi flap would not be transplanted to the dorsum of the foot because of its bulk and the fact that the donor tissue does not match the dorsum of the foot. Other flaps, such as an isolated skin flap (radial forearm flap or lateral arm flap), would be considered better transplants. Similarly, to fill dead space after sequestrectomy of an infected tibia, a lateral arm flap (a small skin flap of 5 7 cm) would not be selected because of a lack of bulk and the fact that muscle flaps are generally more effective in the treatment of osteomyelitis than are skin flaps. The decision to include a skin paddle with muscle flaps is based on the need for contouring or for monitoring the perfusion of the flap. The next consideration is whether dead space needs to be filled. If a flap is used purely for resurfacing (such as the dorsum of the hand so that tendon reconstruction can be performed), a large bulky flap is not required. However, if there is significant dead space, a large muscle flap, such as the latissimus dorsi, should be considered. Osseous free flaps are transplanted to reconstruct structural defects, such as intercalary bone defects resulting from trauma, tumor, or infection. Not all flaps are selected to replace missing tissue. There are instances in which tissue coverage exists but is insufficient in texture and quality, such that the existing soft-tissue envelope needs augmentation. Some free flaps are performed for purely aesthetic reasons, such as resurfacing extremities. This is an unusual use of free-tissue transfer, and it is only selected in certain cases. TRAUMA In attempts to salvage massive lower extremity injuries, soft-tissue coverage is no longer a limiting factor due to the recent advances in microvascular composite tissue transfer. Broader categories of patients are now consid-

Vol. 108, No. 4 / LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION 1031 ered potential candidates for limb salvage. The main indications for salvage of a severely damaged limb include any limb in a child or, in adults, limbs with intact sensibility. Nerve injuries do not preclude salvage, but they should be distal enough to permit the return of some function (primarily sensory) within a reasonable amount of time. Conversely, complex lower limb injuries with nerve damage are frequently considered for amputation, because the return to a functional status with an appropriate prosthesis fitting is usually more rapid. 7 Advanced age should not be a contraindication to the microvascular limb salvage procedures. Careful preoperative patient evaluation and perioperative monitoring can effectively decrease morbidity and mortality rates to those found in younger patients. Lower extremity microvascular reconstruction can be performed safely and successfully in the elderly patient. 8 The initial treatment should include debridement of the devitalized and contaminated tissue and stabilization of fractures. Patients with severe limb injury will often have sustained, major vascular injury in the area of the trauma. Leg perfusion should be assessed clinically and, if needed, an arteriogram should be considered if the zone of injury is large and in the region of potential microvascular anastomosis. The necessity of angiography, however, especially after trauma, is subject to debate. The large experience gained in reconstructive microsurgery has enabled us to become familiar with the vascular anatomy in all regions of the body and to overcome unpredictable intraoperative findings. A meticulous clinical evaluation (with Doppler mapping) can give valuable information without the need for routine recipient-site angiography. 9 The concept of zone of injury refers to the inflammatory response of the soft tissue of the traumatized lower limb that extends beyond the gross wound and results in perivascular changes in the blood vessels. These changes include increased friability of the vessels and increased perivascular scar tissue, which can contribute to a higher failure rate, especially in lower limb free-tissue transplantation, presumably due to a higher rate of microvascular thrombosis. 10 Most surgeons avoid the zone of injury by extensive proximal dissection of the recipient vascular pedicle, and some of them use vein grafts in lower limb reconstruction. Isenberg and Sherman 11 demonstrated that clinical acceptability of the recipient pedicle (vessel wall pliability and the quality of blood from the transected end of the vessel) is more important than the distance from the wound. Park et al. 12 tried to develop an algorithm for recipient vessel selection in free-tissue transfer to the lower extremity. On the basis of their experience, the most important factors influencing the site of recipient vessel selection were the site of the injury and the vascular status of the lower extremity. The type of flap used, method, and site of microvascular anastomosis are less important factors in determining the recipient vessels. 12 TIMING FOR LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION The timing of definitive wound management (such as free-tissue transfer) in the injured extremity is usually determined by factors such as the general condition of the patient and the condition of the wound. The bacterial status of the wound, type of fracture, different types of tissues involved in the injury, and the exposed structures are factors that influence the timing of wound closure. Early aggressive wound debridement and soft-tissue coverage with a free flap within 5 days reduced postoperative infection and decreased flap failure, nonunion, and chronic osteomyelitis. 13,14 Godina 15 emphasized the pathophysiology of high-energy trauma and the emergency (during the first operation) or the importance of radical debridement and early tissue coverage within the first 72 hours. Lister and Scheker 16 reported the first case of an emergency free flap transfer to the upper extremity in 1988, and they defined the emergency free flap as a flap transfer performed either at the end of primary debridement or within 24 hours after the injury. 16 Yaremchuk et al. 17 recommended that flaps be transferred between 7 to 14 days after injury and after several debridements. The argument in favor of this approach is that the zone of injury, which may often not be apparent at presentation, can be determined by serial debridement performed in the operating room over several days. Acute coverage by day 5 to 7 is generally accepted as having a good prognosis in terms of decreased risks of infection, flap survival, and fracture healing. When deciding to perform primary closure with a free flap, two keys factors should be considered: the presence of an exposed vital

1032 PLASTIC AND RECONSTRUCTIVE SURGERY, September 15, 2001 structure and the risk of infection. A vital structure is defined as one that will rapidly necrose if not covered by adequate soft tissue. 18 The decision of what constitutes a vital structure depends on circumstances. Tissues such as vessels, nerves, joint surfaces, tendons, and bone denuded of periosteum may lose function and may create an environment resulting in infection when left exposed for long periods of time. In the decision-making process, the surgeon must consider the risk of leaving the vital structure exposed, its functional importance, and the probability of differential recovery of function considering primary or delayed primary coverage. The risk of infection is the second important factor that should be considered because it may jeopardize the limb, the quality of the functional recovery, or the free flap. As the risk of infection increases, the wisdom of primary closure with a free flap is reduced. Debridement of the wound is the most powerful tool of the surgeon to reduce the risk of infection in the wound. If radical debridement is not possible, a primary free flap transfer should not be considered. Another perspective is that the capability to perform free-tissue transfer allows the surgeon increased freedom to perform radical debridement and may actually reduce the risk of infection. 19 Factors such as the mechanism of injury, the elapsed time, and the degree of contamination of the wound should be considered to evaluate the degree of wound infection more accurately. In an acute, sharp, noncontaminated injury, when closure would be routinely performed if there were no skin loss, there seems to be little reason not to consider an emergency free flap. The choice of flap to be used for wound coverage is determined by the size of the wound, the type of tissue deficit, the state of the wound (colonization and amount of cavitation), the location of the injury, and the length of the pedicle needed. The anastomosis should be done in a safe zone, where recipient vessels have not been damaged by the initial trauma. This is not always possible, but it is recommended. It is usually possible to perform anastomosis outside the zone of injury, either proximal or distal to the zone of injury. Reconstruction of the traumatized leg can be challenging due to the fact that both bony stabilization and soft-tissue coverage are required for a successful functional outcome. Free-tissue transfer using microsurgical techniques has allowed surgeons to salvage traumatized extremities in patients who would formerly have required amputation. 4,5,6 ORTHOPEDIC SEPSIS Osteomyelitis is now a treatable disease. The classic treatment of osteomyelitis includes thorough debridement of infected bone and necrotic tissue, appropriate antibiotic therapy and, if necessary, subsequent closure of the resultant dead space with well-vascularized tissue. 20 The management of dead space after sequestrectomy relies heavily on the technique of free-tissue transfer. 23 Free muscle flaps provide coverage for the debrided bone and soft tissue, obliterate dead space, improve vascularity, and enhance leukocyte function. 21,22,24 Advances in skeletal reconstruction and fixation have improved the treatment of patients with osteomyelitis and large (greater than 6 cm) segmental bone defects. In the past, despite successful treatment of osteomyelitis, some patients required amputation due to chronic nonunions. Now, once the bone infection is treated, vascularized bone transplants 25,26 or bone lengthening using the Ilizarov technique facilitate reconstruction and provide structural stability for limb function. 27 Distraction osteogenesis (i.e., the Ilizarov technique) is the process of bone transfer relying on the principle of callus formation and distraction after corticotomy. Local muscles were traditionally used to treat chronic osteomyelitis, and free flaps have been described more recently for this use. Local gastrocnemius and soleus muscle flaps are still used to cover smaller wounds on the upper and middle thirds of the leg, respectively. However, local muscle flaps will not reliably cover defects larger than 25 cm 2 or those on the distal third of the leg, ankle, or foot. For these defects, free muscle transfers are preferred. The advantages of using the free muscle flaps, such as the latissimus dorsi, 28 serratus anterior, 29 and rectus abdominis, 30 instead of local pedicled muscle flaps, such as the gastrocnemius muscle, are that free flaps provide greater bulk (filling larger wounds), have longer pedicles (increasing flexibility in muscle positioning), and carry larger diameter vessels (facilitating the microanastomoses).

Vol. 108, No. 4 / LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION 1033 TUMORS Over the last decade, microsurgical techniques have been increasingly used to reconstruct bone and soft-tissue tumors in the lower extremity. Specifically, with the emphasis placed on limb salvage after compartment resection rather than amputation, microsurgical techniques have allowed the orthopedic oncologist and reconstructive surgeon to work together, resulting in limb preservation. Specifically, in soft-tissue sarcoma, where entire compartments are resected, microsurgical transplantation replaces components of both muscle and skin to maintain limb contour and aid in healing. For example, a large anterior compartment resection for a malignancy may expose the tibial cortex. Microsurgery is the only reconstructive option for wound closure. A flap such as the latissimus dorsi muscle could be used to cover the tumor defect. This muscle can also be innervated to assist in dorsiflexion of the foot. The radiated wound, particularly after the treatment of soft-tissue sarcomas, has a high incidence of wound complications after attempted primary closure. Radiated wounds generally have a poor vascular supply, making surgery through these wounds difficult and prone to breakdown. Importing well-vascularized tissue into the wound results in more rapid wound healing and may improve local circulation in radiated areas. For this reason, many centers have adopted the policy that immediate microsurgical reconstruction be performed after tumor extirpation. The results of immediate microsurgical transfers in these cases have been well substantiated and have led to decreased hospital time, decreased costs, decreased morbidity, and increased rate of limb salvage and high patient satisfaction. 31 The traditional treatment for high-grade sarcomas of bone, such as osteosarcoma, was amputation before the advent of free-tissue transfer. Limb salvage surgery has become a viable alternative for many patients due, in part, to the development of more effective perioperative chemotherapy. The success of limb salvage in these patients primarily depends on wide resection margins and the addition of perioperative chemotherapy. The current management of soft-tissue sarcomas or osteogenic sarcomas stresses more conservative resection and limb-sparing operations. Local flaps generally do not provide adequate coverage, and freetissue transfer is often the only option. This type of resection creates complex composite defects of bone and soft tissue that require the use of composite flaps in the reconstructive process, such as an osteocutaneous fibula flap for an intercalary bone defect that also has an accompanying overlying skin defect. 32 Approaching these cases with a multidisciplinary team facilitates the planning of the surgical resection, oncologic treatment, and reconstruction timing. Operative details such as incisions, design of skin flaps, exposure, and preservation of the recipient site vessels should be carefully planned with the ablative surgeon. It is usually possible to establish the soft tissue and bony requirements of the wound early in the operation and to begin the flap harvest concurrent with the tumor resection. If oncologic margins are not predictable, then it is best to complete the resection before beginning dissection of the free flap. 33 Flaps are indicated to cover neurovascular structures (particularly if radiated), bone devoid of periosteum, and allografts or tumor prostheses that cannot be covered with local tissues. Sometimes blood supply to local flaps may be killed during tumor resection. Patients who undergo secondary reconstruction can be subdivided into two groups. The first includes those who undergo tumor resection and develop acute wound complications such as skin flap necrosis in the early postoperative period. These patients may require debridement and free flap coverage within the first or second postoperative week. It is safe to let questionable areas demarcate before surgery. Patients who present later with impending allograft or prosthesis exposure should undergo surgery as soon as possible to avoid infection of the implant or allograft. The second group of patients require reconstruction several months or years after primary tumor resection. Some of the patients in this group present with chronic unstable soft-tissue coverage, wound dehiscence, prosthesis infection, and prosthesis failure or limb growth that compromises soft tissue. Although free-tissue transfer adds extra time and technical complexity to the tumor operation, it may also lead to a decrease in amputation rates by decreasing wound complications. In addition, it allows the oncologic surgeon to obtain adequate margins of resection, which may favorably influence amputation rates by contributing to a decrease in local recurrence.

1034 PLASTIC AND RECONSTRUCTIVE SURGERY, September 15, 2001 DYSVASCULAR AND DIABETIC FOOT Nonhealing wounds of the extremities are common in patients with diabetes and peripheral vascular disease. The magnitude of the problem is enormous, with statistics indicating that 14 percent of diabetic patients are hospitalized an average of 6 weeks per year for foot problems and more than 80 percent of amputations are in diabetics. Even the contralateral limb is at risk in these patients for further ulceration, and there is a 50 percent chance of loss of this leg within 5 years. 34 The approach to these patients involves a close collaborative effort among the orthopedist, the peripheral vascular surgical team, and the microsurgical team to optimize the ability to obtain a rapid and accurate diagnosis and to assess the vascular problem, the most appropriate and timely plan for wound care, and the most reliable revascularization. The results of macrovascular and microvascular anastomoses are comparable to those in nondiabetic patients undergoing the same procedure. 35 Diabetic patients have higher local morbidity and a high incidence of reoperation. Patients treated with cutaneous free flaps have lower morbidity than patients treated with muscle free flaps. 36 The cutaneous radial forearm free flap is an excellent option for treating relatively small wounds of the foot because it provides tissue with a lengthy vascular pedicle and a donor site that can often be closed primarily. Despite the global set of underlying medical problems in this type of patients, mortality rates are not higher in cases in which microsurgery reconstruction procedures are done alone or in combination with vascular reconstruction. 37 The general trend today is that once the extremity has been revascularized, the most appropriate method of reconstruction can be carried out for defects of the foot in a well-vascularized limb. For these patients, in whom the macrovascular blood supply is intact and who have apparent compromise but large, unhealthy, colonized wounds involving major soft tissue or involving tendon or bone, free flap coverage is indicated. Free-tissue transfer techniques are ideal in these situations because (1) they are able to resurface any size defect; (2) they allow aggressive resection of the wound to get rid of colonized, fibrotic, unhealthy tissue; (3) the flap actually helps revascularize the defect; and (4) the defect is replaced with healthy, nondamaged tissue. Diabetic and dysvascular patients require a high degree of vigilance to avoid problems, both locally and systemically, with much closer observation of the donor sites and recipient sites to preclude a higher rate of wound healing problems. Because many diabetic/dysvascular patients having a free flap are candidates for amputation before flap transfer (which is often offered as a last option before limb loss), these procedures do not increase the rate of limb loss; instead, they can only increase the limb salvage rate. It is important to examine the results of lower extremity limb salvage as it relates to ambulatory function. Salvage of a nonuseful limb in such patients is of little value in their overall management. Likewise, heroic attempts at salvaging a limb are not indicated if the operation puts excessive stress on the patient (such as a patient with cardiovascular disease). A high degree of success can be achieved only by extremely careful patient selection. In the face of systemic difficulties, one must also exercise proper judgment and abort attempted reconstruction to insure patient survival. Chronic venous ulcers can be also treated with microsurgical transfers. In appropriate patients with a localized disease, a dual surgical approach including wide excision of the ulcer and surrounding liposclerotic tissue bed and replacement by a free flap containing multiple competent microvenous valves with a normal circulation may improve the underlying pathophysiology. Free flaps can increase the blood supply to compromised areas and provide coverage of exposed bones, joints, or tendons. This can be accomplished in one reconstructive procedure with excellent long-term results. In patients with complex ischemic or infected wounds from diabetes, free-tissue transfer as an adjunct to lower extremity vascular reconstruction can help in obtaining a salvageable functional limb, thus presenting a viable alternative to amputation 38,39 ILIZAROV TECHNIQUE New evidence suggests that a simultaneous Ilizarov procedure and microsurgical tissue transplantation is even a higher rung on the reconstructive ladder. In combination with microsurgical transplants, the Ilizarov procedure may provide the best reconstructive option for extremity reconstruction. The combined versatility of modern free-tissue transplantation and the Ilizarov method has taken limb salvage to

Vol. 108, No. 4 / LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION 1035 the next level. Four possibilities for combined Ilizarov procedure and microsurgery exist. The first is the use of the Ilizarov technique with an external fixator for bone stabilization in cases of open fractures. In these cases, adequate bone stock is present and will consolidate, usually without a bone graft, provided soft-tissue coverage is achieved. The request for coverage may occur after the orthopedic traumatologist places the Ilizarov frame and recognizes the need for augmentation of the soft-tissue envelope. Trends toward a multidisciplinary approach in lower extremity trauma care involve orthopedic and plastic surgeons coordinating their efforts at the time of initial evaluation of the patient. This will allow the planing of emergent or early coverage (within 3 days) and proper pin and ring placement. In these cases, free-tissue transfer provides only coverage, and the frame provides definitive fracture care with options for progressive dynamization by frame disassembly, decreased rigidity, and increasing load to allow bone healing to occur. The second combination of Ilizarov technique with microsurgery is the application of the Ilizarov procedure after flap placement to correct an evolving deformity, such as in the treatment of nonunion or malunion. Although the Ilizarov method can treat deformities or malunions without free-tissue transfer, there is a large group of patients who undergo initial stabilization with plates or conventional external fixators who then undergo flap coverage and, after the soft tissue heals, the bone does not heal or begins to heal with an axial deformity due to weight-bearing. If this is recognized early, the Ilizarov technique can be used to align, acutely or gradually, the nascent malunion after replacing the initial external fixator. If this occurs late, with bone healing in malalignment, the Ilizarov method can be used to realign the limb after an osteotomy through the malunion. In large segmental defects, the Ilizarov technique can be used to treat the initial fracture by stabilization, followed by callous distraction after the soft tissue is healed. In cases of bone loss, the bone defect can be filled by two methods acutely shortening the bone, then gradually lengthening it to restore the original bone length or bone transport to gradually fill the defect. 40,41 Acute shortening and subsequent lengthening at a site distant from the fracture is indicated in cases requiring nerve or vessel repair. Another advantage is that fracture fragments can be reduced and stabilized under direct vision because these fractures with bone loss always have a soft-tissue defect in this area. Disadvantages of this technique are that in treating tibial fractures with bone loss, the fibula should also be shortened, usually by an osteotomy through a separate incision. In addition, blood vessels and nerves may be kinked by the shortening. Free flaps are often used to reconstitute the soft-tissue envelope used in these cases. The surface area and the volume of free flaps are diminished, so the morbidity of the donor site is decreased. For example, in a large soft-tissue injury with an open tibia fracture, the latissimus dorsi may have been previously selected for coverage. But by acutely shortening the limb and decreasing the soft-tissue defect, a gracilis or slip of serratus may be harvested. This fulfills the soft-tissue requirements and usually involves an easier flap with less morbidity. Bone transport using the Ilizarov method (distraction osteogenesis) is the fourth technique used to fill bone and soft-tissue defects. This technique maintains the length and alignment of the extremity. The bone defect is filled by first performing a corticotomy at a site proximal, distal, or both proximal and distal to the defect. The defect is gradually filled by an internal lengthening, which is accomplished by transporting the osteotomized segment toward the defect at a rate of 0.5 to 1 mm/day. Several advantages of the bone transport method exist compared with acute shortening. Theoretically, almost no limits exist regarding the amount of bone loss that can be filled with this technique. The length and alignment of the extremity are maintained throughout treatment, allowing maximum function and, in the lower extremity, complete ambulation. The soft tissues attached to the transport segment are also transported toward the defect, allowing closure of some soft-tissue defects without the use of flaps or grafts. 42 Perhaps the most significant disadvantage is that subsequent surgical procedures may be needed as docking occurs to reshape the ends of the fragments and graft with autogenous bone. To accelerate bone union, Green advocates trimming the ends and adding an autogenous bone graft. 40,43 The Ilizarov method may be used as a definitive fixation technique for vascularized bone grafts that are used for bone defects that ex-

1036 PLASTIC AND RECONSTRUCTIVE SURGERY, September 15, 2001 ceed 6 cm. The osteoseptocutaneous fibula is our first choice, and it has been the work horse flap in such cases. Internal fixation, such as plates or intermedullary nails, to secure intercalary vascularized fibular grafts can be avoided with the Ilizarov technique. In instances of osteomyelitis, the soft tissue can be managed with free-tissue transfer and the Ilizarov can be used to bridge unstable defects requiring conventional or vascularized bone grafts. Similarly, in instances of tumors requiring large intercalary resections, the Ilizarov method can be used as a holding device for allograft and vascularized fibular combinations. Technical points, such as the configuration of the flap with its vascular pedicle, should be taken into consideration and carefully planned in terms of the future movement of bone and soft tissue. The vascular pedicle and anastomosis site should be located in the tissue that moves together with the transferred flap to avoid undue forces on it. 44 FREE VASCULARIZED BONE GRAFTS Current indications for free vascularized bone grafting are broad. Vascularized bone grafting offers significant advantages in bone defects larger than 6 to 8 cm in length resulting from trauma or infection requiring extensive sequestrectomy. 45,46 Other indications include refractory nonunion, with failure of conventional techniques, and congenital pseudoarthrosis of the tibia or forearm. 47 Future applications may include the transfer of a vascularized epiphysis to reconstitute limb growth 48 and the transfer of free vascularized allografts. 49 The transfer of vascularized bone has had a considerable impact in lower extremity reconstruction. The fibula, iliac crest, and (occasionally) ribs are the vascularized bones most often transferred to repair posttraumatic leg defects. MICROSURGERY FOR AMPUTEES Once amputation is inevitable, the main objective of surgery is to preserve a functional stump. Free-tissue transfer is a valuable tool in preserving the length and restoring the contour of the lower limb stump. Parts from the amputated limb, such as calcaneal-plantar unit, and classic free flaps, such as the latissimus dorsi, scapula, and anterior lateral thigh flaps, can be used to achieve a good, rapid rehabilitation of the patient. 50,51 The free fillet flap principle was described as a part of the spare part preservation. 52 This strategy allows the harvesting of flaps without additional donor site morbidity. This strategy can be applied on the basis of an immediate use of the flaps 53 and a multistaged reconstruction with banking of the free flaps. 54 Recently, this technique was also applied in cases of tumor resection to achieve defect coverage that emphasized the use of free fillet flap. 55 MONITORING Monitoring free-tissue transfer is essential to assure transplant success. Many different monitoring devices and techniques have been used with varying levels of success. There is no ideal flap monitoring system, but improving the existing monitoring techniques and a better understanding of the information they give will help improve the salvage rate in cases that develop complications. Clinical evaluation remains the gold standard by which all methods of monitoring need to be compared. This involves observing skin color, temperature, capillary refill, and bleeding characteristics. Changes are often initially subtle and, by the time they are clinically apparent, salvage of the flap may be impossible because of irreversible tissue damage. The standard practice in our center is routine monitoring of patients using a laser Doppler; this is usually done in the intensive care unit for the first 24 hours because this is when the problems most frequently occur after freetissue transfer. We usually monitor the numbers and the general trend of the values, which in our opinion can indicate a problem at an earlier stage. FLAP COMPLICATIONS AND MANAGEMENT Acute complications occur usually in the first 48 hours and include venous thrombosis, arterial thrombosis, hematoma, hemorrhage, and excessive flap edema. Arterial insufficiency can be recognized by decreased capillary refill, pallor, reduced temperature, and the absence of bleeding after pinprick. This complication can be caused by arterial spasm, vessel plaque, torsion of the pedicle, pressure on the flap, technical error with injury to the pedicle, a flap harvested that is too large for its blood supply, or small vessel disease (due to smoking or diabetes). Management of arterial compromise requires prompt surgical intervention to restore the blood flow. 56 Pharmacological inter-

Vol. 108, No. 4 / LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION 1037 vention includes vasodilators, calcium blockers, and anticoagulants for flap salvage presenting with arterial insufficiency. 57 Venous outflow obstruction should be suspected when the flap has a violaceous color, brisk capillary refill, normal or elevated temperature, and produces dark blood after pinprick. Venous insufficiency can occur due to torsion of the pedicle, flap edema, hematoma, or tight closure of the tissue over the pedicle. Venous outflow obstruction can result in extravasation of the red blood cells, endothelial breakdown, microvascular collapse, thrombosis in the microcirculation, and flap death. Given the irreversible nature of the microcirculatory changes in venous congestion that occur even after short periods of time, the surgeon must recognize venous compromise as early as possible. These complications can occur alone or in any combination. Clinical observation and patient monitoring (such as with laser Doppler) should alert the surgeon to complications; the surgeon must then decide between conservative and operative intervention. Conservative treatment may include draining the hematoma by the bedside release of a few sutures to decrease pressure. In cases of venous congestion, leeches may be helpful if insufficient venous outflow cannot be established, despite a patent venous anastomosis. The leeches inject a salivary component (hirudin) that inhibits both platelet aggregation and the coagulation cascade. The flap is decongested initially as the leech extracts blood and is further decongested as the bite wound oozes after the leech detaches. 56 The donor site should be given the same attention as the recipient site during the postoperative period. Complications of the donor site include hematoma, seroma, sensory nerve dysfunction, and scar formation. FLAP FAILURE AND MANAGEMENT Occasionally, free flaps fail, despite early return to the operating room for vascular compromise. Options for management include the performance of a second free-tissue transfer, noting the technical or physiologic details that led to initial failure. Most of the time, freetissue transfers fail due to technical errors in judgment, which can include flap harvest, compromise of the pedicle during the harvest, improper microvascular technique during anastomosis, improper insetting resulting in increased tissue tension and edema, and postoperative motion of the extremity resulting in pedicle avulsion. Although rare, avulsion does occur. The next decision made by the operating surgeon regarding the management of the patient is based on several factors. Obviously, if a patient requires a free flap in the first place, a second free flap should be considered. If a decision is made not to redo the flap, it could be left in place using the Crane principle in hopes that underlying granulation will be sufficient such that skin grafting can be performed once the necrotic flap is removed. The Crane principle is based on the fact that a local flap or a free-tissue transfer that necroses in part or totally can act as a biological dressing or eschar over a wound bed. If there is no infection, then the eschar can be left on the wound bed with hopes that some healing can occur underneath the eschar. This would be in the form of granulation tissue that may form under the eschar. Ultimately, the eschar could be removed and, with an appropriate granulation bed, the wound can be skin-grafted, thus obviating the need for another free-tissue transfer. By observing the wound, if such a bed is not produced, then a second flap must be considered. 58 We prefer not to leave the necrotic flap in place because the flap can become a source of sepsis and further compromise local tissues. Necrotic, nonviable flaps should be removed, and a temporary wound dressing, such as a bead pouch or wound vacuum-assisted closure, should be used. Occasionally, when flaps fail in severely compromised extremities, consideration can be given to amputation in that the morbidity of a second free-tissue transfer and perhaps the resultant extremity state renders the extremity less favorable for salvage and more favorable for amputation. If a second free flap is considered, obvious errors that lead to flap compromise need to be recognized. It may be prudent to obtain an arteriogram, evaluate the coagulation profile, and research other issues that lead to failure. INFORMED CONSENT AND MEDICAL/LEGAL ISSUES Informed consent for free transfer should include an explanation of the principles of microsurgical tissue transplants and the advantages and disadvantages of the procedure. The patient should understand the risk of vascular thrombosis, flap failure, loss of limb, and nerve injury. The risks include continued infection,

1038 PLASTIC AND RECONSTRUCTIVE SURGERY, September 15, 2001 persistent nonunion, and limb losses, with or without a successful flap. No guarantees should be given regarding the surgical outcomes. The possibility for salvaging a significantly compromised extremity can be offered using microsurgical techniques, either with or without a successful free flap. Limb amputation after freetissue transfer can be performed for reasons of pain, sepsis, or persistent bone instability. AESTHETIC CONSIDERATIONS AFTER LIMB TRAUMA The final stage of the reconstructive ladder involves the issue of aesthetic restoration of the limb. Not infrequently, patients are traumatized by scars, skin grafts, and bulky free flaps, and consideration should be given to the psychological comfort of the patient in addressing these issues. The reconstructive ladder could involve the use of staged excision of scars, scar revision, dermabrasion, and tissue expanders to expand the normal skin, recruiting dermal and epidermal elements, followed by transposition of these expanded skin segments to stage out or eliminate unsightly scars. In some instances, even free-tissue transplantation can be performed for aesthetic recontouring of limbs, which can be of major psychological benefit to patients and may even allow further reconstruction, if necessary. FUTURE TECHNOLOGY: PREFABRICATION AND ENDOSCOPIC HARVEST The recently developed endoscopicallyassisted flap harvest through small incision(s) aims to circumvent the disadvantages of the traditional harvesting techniques. 59,60 Besides, this minimally invasive approach also offers several potential theoretical advantages over traditional harvesting techniques. Magnified visualization of the operative field through the video monitor can help surgeons achieve better intraoperative hemostasis with less postoperative bleeding. Small incisions can potentially result in better wound healing, less nursing care, and less postoperative pain at the donor site. However, these benefits of a minimallyinvasive endoscopic technique must be weighed against the increased complexity of operating room setup, which leads to an increased operative time and cost. Because of lack of tactile sensation and two-dimensional video monitor visualization, the endoscopic technique requires a learning curve after traditional surgical training. Furthermore, donor site morbidity in the endoscopically assisted and traditional techniques must be compared to determine whether this new trend is justified. Recent studies comparing traditional and endoscopic harvesting of latissimus dorsi flaps revealed no statistically significant differences in the amount of intraoperative bleeding, the incidence of postoperative hematoma and seroma, and the incidence of donor-site wound infection, as assessed by the surgeon. However, a patient questionnaire revealed that although it did not reach statistically significance, endoscopically assisted harvest of the latissimus dorsi muscle resulted in less pain and allowed earlier and better movement of the upper extremity at the donor site. The patients attitude and feeling about the scar and overall satisfaction were also higher in the endoscopic group. 61 The search continues for new methods that will result in faster and easier microvascular anastomosis. Thus, staplers may have a more important role in microsurgery in the future. They shorten the operating time and have been proven safe. 62 The vessels suitable for this technique should be chosen carefully, and the surgeons using this technique should also be experienced in conventional microsurgery. We expect that the time-consuming procedure of microvascular surgery using interrupted sutures will be replaced by the use of running sutures. Furthermore, refinements in laser welding and the development of new glues may lead to the replacement of sutures by these techniques. The operating microscope itself may also vanish in time. Many microsurgeons prefer to use high-magnification loupes, with which they are able to achieve good results. 63,64 Furthermore, advances in video technology now enable the surgeon to view a microsurgical field on a monitor in three dimensions without the need to look through the microscope eyepieces. 65 Flap prefabrication allows for custom flaps to be constructed on the basis of what is required for a specific defect. The exploration of this new frontier may increase the possibility of reconstructive capabilities and decrease the donor morbidity of classic reconstructions. Current clinical methods of flap prefabrication are based on one or more of the following fundamental principles of reconstructive surgery: (1) delay or expansion; (2) grafting (pretransfer flap grafting of flaps is necessary when complete graft take is mandatory to the success

Vol. 108, No. 4 / LOWER EXTREMITY MICROSURGICAL RECONSTRUCTION 1039 of the reconstruction and when post-transfer grafting is neither feasible nor practical); and (3) vascular induction using staged flap transfer. This third method is based on the wellestablished principle of staged flap transfer, for which the vascular carrier is the contemporary microvascular refinement of the old wrist carrier. The concept is that a small flap of muscle, fascia, omentum, or even an arteriovenous bundle or fistula can become a vascular carrier and can be induced to provide an alternative blood supply through neovascularization to a larger block of tissue after a relatively short staging period. 66 A fourth method of flap prefabrication makes use of recent advances in cell biology to induce the transformation of a flap from one tissue type to another. An application of these advancements can be found in bone and joint reconstruction, which is still most commonly performed with less than ideal alloplastic materials and remains a formidable challenge, despite advances in free-tissue transfer. With the possibility of inducting mesenchymal tissue to differentiate into bone, a simple muscle flap may be molded and transformed into a vascularized bone graft of the desired shape and size. 67,68 COST AND OUTCOME The time-consuming and costly nature of these expensive and sophisticated procedures versus straightforward amputation cannot be ignored. Although the exact cost of leg salvage is difficult to determine, even in highrisk groups of patients such as diabetic patients, salvage may be less expensive than the combined cost of hospitalization, prosthesis fitting, rehabilitation, and disability payments. Some groups have assembled cost estimates and made initial inroads into outcomes and measurements of the cost-effectiveness of reconstruction procedures. 69,70 The versatility and vascularity of free-tissue transfers have made them indispensable tools in lower limb reconstruction. Although free flap procedures can provide definitive treatment in a single operation, they are expensive and require specialized practitioners. The cost of microsurgery in treating the spectrum of eligible patients has not been defined. Clearly, a reduction in complication rates would reduce the cost of these procedures. Currently, efforts are underway to reduce free flap costs at all stages of care by shortening the operating time with the use of new devices, shortening the monitoring time postoperatively, and even exploring the possibility of using an outpatient monitoring system in selected patients. 71 In this area of managed care and capitation, expensive procedures are often targeted in cost-containment efforts. Free flap procedures are costly, but they are also effective. 72 L. Scott Levin, M.D. Division of Plastic, Reconstructive, Maxillofacial, and Oral Surgery Duke University Medical Center Durham, N.C. 27710 levin001@cmc.duke.edu REFERENCES 1. Jacobson, J. H., II, and Suarez, E. L. Microsurgery in anastomosis of small vessels. Surg. Forum 11: 243, 1960. 2. Buncke, H. J., Jr., and Schulz, W. P. Experimental digital amputation and replantation. Plast. Reconstr. Surg. 36: 62, 1965. 3. Kleinert, H. E., Kasdan, M. L., and Romero, J. L. 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Vascularized bone autografts: Experience with 41 cases. Clin. Orthop. 174: 87, 1983. 47. Chen, C. W., Yu, Z. J., and Wang, Y. A new method of treatment of congenital tibial pseudoarthrosis using free vascularized fibular graft: A preliminary report. Ann. Acad. Med. Singapore 8: 465, 1979. 48. Nettelblad, H., Randolph, M. A., and Weiland, A. J. Free microvascular epiphyseal-plate transplantation: An experimental study in dogs. J. Bone Joint Surg. (Am.) 66: 1421, 1984. 49. Doi, K., Akino, T., Shigetomi, M., et al. Vascularized bone allografts: Review of current concepts. Microsurgery 15: 831, 1994. 50. Malikov, S., Dubert, T., Koupatadze, D., et al. Lower limb stump reconstruction with a functional calcaneoplantar unit free flap: A series of 16 cases. Ann. Chir. Plast. Esthet. 44: 163, 1999. 51. Shenaq, S. M., Krouskop, T., Stal, S., et al. Salvage of amputation stumps by secondary reconstruction utilizing microsurgical free-tissue transfer. Plast. Reconstr. Surg. 79: 861, 1987. 52. Chiang, Y. C., Wei, F. C., Wang, J. W., et al. Reconstruction of below-knee stump using the salvaged foot fillet flap. Plast. Reconstr. Surg. 96: 731, 1995. 53. Weinberg, M. J., Al-Qattan, M. M., and Mahoney, J. Spare part forearm free flaps harvested from the amputated limb for coverage of amputation stumps. J. Hand Surg. (Br.) 22: 615, 1997. 54. Jennings, J. F., Murphy, R. X., Jr., Chernofsky, M. A., et al. Amputation stump salvage using a banked freetissue transfer. Ann. Plast. Surg. 27: 361, 1991. 55. Cordeiro, P. G., Cohen, S., Burt, M., et al. The total volar forearm musculocutaneous free flap for recon-