Free tissue transfer is a powerful tool for the reconstructive surgeon, but it has limitations. Free tissue transfer affords the opportunity to recruit uninjured specialized tissues into a wound not only to provide coverage but also potentially to return function. This procedure requires an extensive team of specially trained surgeons, nurses, technicians, and a complement of costly, specialized equipment.11,47,48
The key to success of free tissue transfer is the placement of multiple lumen-inverting sutures to oppose endothelium and exclude from the anastomosis local thromboinducive tissue, namely the adventitia. Trauma to the endothelium during the microsurgical anastomosis must be avoided, and endothelium with preexisting injury due to the war injury must be excluded.
The site of anastomosis should ideally be entirely free of trauma and inflammation. As previously discussed, very often the zone of injury extends well into the leg and even the thigh. In such cases, free tissue transfer may be considered too risky and thus abandoned in favor of another form of wound management. Plain films should be scrutinized for evidence of deep penetration of debris far beyond the foot and ankle even when only relatively minor skin wounds are found on examination. The authors routinely use computerized tomographic angiography (CTA) to determine whether potential recipient vessels have sustained trauma. On several occasions, the site of microanastomosis was changed or free tissue transfer was not performed, due to the discovery of vessel injury on CTA. End-to-side arterial anastomosis is performed when possible to avoid sacrificing a main artery. However, end-to-end anastomosis is chosen if the recipient artery is small and the vascular status of the foot is such that sacrificing a main artery would not be too detrimental.
As the patient is brought into the room and positioned, 300 mg of aspirin is given per rectum. Postoperatively it is continued orally at 325 mg daily for 1 month. Detailed attention is given to patient positioning. Harvesting and insetting the flap at the recipient site is typically time consuming, requiring the patient be protected from accidental vessel, nerve, and skin compression. Arterial monitoring is often performed by the anesthesia provider. If this is done before arrival in the operating room, time is saved. The patient arrives in the operating room hemodynamically optimized, but is typed and cross-matched for possible transfusion. Due to the need for access to the donor and recipient sites, the patient may remain very exposed after prepping and draping. Therefore, arranging blanket and warmer cover for the patient without compromising the surgical fields is very important. The table and patient are positioned with thought to where the microscope will be brought in and to where 2 microsurgeons will operate. The surgeons should be in a comfortable sitting position; rarely the microvascular anastomosis must be done with the surgeons standing. The patient’s position may be reversed on the operating table to prevent the main post from interfering with the surgeons’ legs. Prophylactic antibiotics are given at the beginning of the procedure and at routine intervals thereafter. The operating room personnel ideally are familiar with the technique and requirements of performing microvascular free flaps. This knowledge includes the ability to prepare the necessary instruments, equipment, and fluids so that they are readily available when needed. If a monitor is available to connect to the microscope, all individuals in the room may observe the microscopic part of the case, which will allow them to anticipate needs and avoid inefficiency resulting from boredom and distraction.
Two surgical teams with 2 trained and credentialed microsurgeons are preferred, not only to minimize surgical time for the patient but also to minimize surgeon fatigue. This teamwork is particularly important in facilities that perform high volumes of free tissue transfers. While the donor site is dissected, any preliminary surgery on the recipient site is performed, such as final débridement, bone stabilization, and preparation of the recipient vessels. After the flap is fully mobilized but the pedicle has not yet been divided, and preliminary recipient site preparation has been performed, the 2 surgical teams each take staggered breaks as needed. During this time the remaining team can complete irrigation and débridement, set up the microscope and the microscopic field, further prepare the recipient vessels, and begin closing the donor site. Several minutes before division of the flap pedicle at the donor site, approximately 5000 units of heparin are given intravenously, adjusted according to patient size and weight.
The authors have begun using a continuous tissue oxygenation monitoring system for monitoring the flap post surgery (ViOptix Tissue Oximeter, ViOptix Inc, Fremont, CA). Use of this device entails affixing a sterile probe to a skin paddle of the flap and connecting the probe to a monitor. The monitor measures tissue oxygenation continuously, and provides a constant display of absolute value as well as a running time-based graph. The device is extremely helpful in giving early warning of flap compromise, long before a problem is detected by change in color, temperature, or Doppler signal; its use expedites operative exploration and correction of the problem. In addition to postoperative monitoring, the tissue oxygenation monitor is used during the surgical procedure to give real-time information about the status of the flap during harvest and inset. A baseline tissue oxygenation level is determined after completely mobilizing the flap from the donor site and isolating the pedicle, but before division of the pedicle. This value sets the expectation for tissue oxygenation once the anastomosis is completed. Inadvertent compromise of tissue oxygenation during insetting of the flap and closure of the wound over the pedicle can be immediately identified and addressed.49,50
For muscle flaps, inclusion of a skin paddle is necessary for use of this monitoring device.
After free-tissue transfer, the patient is monitored hourly in the intensive care unit. The tissue monitor and hourly checks are maintained for at least 4 days. If external skeletal fixation is applied, balanced suspension is frequently used to elevate the extremity just above heart level. Balanced suspension is advantageous because it allows the patient to reposition his leg and whole body with minimal effort, as the weight of the leg is counterbalanced. A warming blanket set at medium-high temperature is applied to the extremity to promote vasodilation. The room temperature is set per patient comfort. Intake of nicotine (all tobacco products as well as nicotine patches), caffeine, and chocolate are forbidden due to their vasoconstrictive properties. However, the scientific literature provides strong recommendations only for nicotine.51
Hemoglobin levels are maintained to prevent signs and symptoms of anemia. In case emergent flap exploration is needed, the patient is kept NPO on the first postoperative day, as most cases of flap compromise occur in the first 24 hours post anastomosis. Following this a supplemented regular diet is resumed as soon as possible. In addition to daily aspirin, anticoagulation therapy is administered when indicated for prophylaxis against deep venous thrombosis. Intravenous heparin and Dextran 40 are not routinely given in the postoperative period.
Any sign of vascular compromise is addressed aggressively, with a very low threshold for emergent operative exploration. Bedside troubleshooting is done to rule out faulty monitoring equipment, constrictive dressings, a clogged drain, and compromised limb position; if present these issues are addressed. The operating room is notified and instructed to prepare for the case as if an entirely new flap were to be performed. While operative exploration is arranged, consideration should be given to releasing skin sutures if it is suspected that the skin itself or a wound hematoma is compressing the pedicle. Once in the operating room, the artery and vein are inspected, and the problem is identified and remediated. Although time is of the essence, the microsurgeon must carefully and methodically identify and correct all problems. If needed, all anastomoses are taken down, previously sewn vessels are trimmed to fresh tissue, and the microanastomoses are redone, using vein grafts if needed.
In cases of significant venous congestion, the thrombolytic agent alteplase has been focally infused into the arterial system of the flap (1 mg/5 mL for a total of 3–5 mg) at the time of operative exploration. This infusion has been done only when restoration of adequate venous return is not achieved after its root cause has been identified and corrected. If possible, the alteplase is infused through a side branch of the arterial pedicle, without taking down the anastomosis if it is otherwise pristine and patent.52
Medicinal leeches have been extremely valuable in treating certain cases of venous congestion of free and pedicled flaps.53,54
However, leeches are used in addition to operative exploration. Leeches are only recommended for small flaps. On occasion, a small Fogarty catheter may be used to extract a clot from some flaps; this should be done judiciously to prevent intimal damage to the vessels, which would promote repeat thrombosis.
Below the authors review flaps they have commonly used in free-tissue reconstruction of war wounds to the foot and ankle. Most frequently the authors have used the anterolateral thigh free flap. Other flaps commonly used have included the rectus abdominis muscle free flap and the latissimus dorsi muscle free flap. The authors have not used the lateral arm free flap, the radial forearm free flap, or the gracilis muscle free flap for reconstruction of the foot and ankle due to their satisfaction and experience with the aforementioned. However, these latter flaps are described, and should be considered according to the individual circumstances of the patient and the experience of the surgeon.
Anterolateral Thigh Free Flap
The use of the anterolateral thigh free flap has increased dramatically in recent years due to its recognized reliability, potential size, relative ease of harvesting, and minimal donor morbidity.55,56
Harvesting the flap with the patient in the supine position is an attractive feature of this flap that must not be underappreciated, particularly in the multiply injured war-wounded patient. Although it can become rather thick in obese individuals, this flap generally provides a pliable source of fascia and skin, with a vascular pedicle of 10 to 13 cm in length and up to 2 to 3 mm diameter. Especially in men, it can be quite pileous. The size of this flap can be very large, up to 15 cm in width and 25 cm in length. Primary closure of the donor site is usually possible with flap width up to 8 cm.
The anterolateral thigh free flap is based on a myocutaneous perforator through the vastus lateralis muscle in 84% of cases. Otherwise it is based on a septocutaneous perforator coursing between the vastus lateralis and the rectus femoris muscles. The perforator vessel or vessels generally derive from the descending branch of the lateral circumflex femoral artery, which courses between the vastus lateralis and the rectus femoris, or from a direct branch of the lateral circumflex femoral artery distinct from the descending branch (). Branches of the femoral nerve will be encountered when raising this flap and should be preserved. A portion of the vastus lateralis can be harvested with this flap for use in filling a wound cavity. Although anatomic variation in the anatomy of the skin perforators can make the harvesting of the flap tedious and stressful, experience has demonstrated that the patient surgeon can expect a satisfactory pedicle. Before circumferentially raising the flap, however, the presence of an arterial perforator must be absolutely confirmed.57
The authors always counsel the patient that both thighs may have to be explored for an acceptable flap, but have not as yet had to resort to this. Care must be taken when dissecting the pedicle to avoid muscular branches of the femoral nerve. When combined with a strip of the fascia lata, an Achilles tendon can be reconstructed. A sensate flap can be made by including the anterior branch of the lateral femoral cutaneous nerve and suturing this to a sensory nerve at the recipient site ( and ).
Fig. 11 Vascular pedicle of the anterolateral thigh flap. 1, descending branch of the lateral circumflex femoral artery; 2, musculocutaneous perforator; 3, rectus femoris muscle. 4, vastus lateralis muscle; 5, muscular branch of femoral nerve; 6, lateral femoral (more ...)
Open ankle fracture with extensive soft tissue loss.
Inset of free anterolateral thigh flap to open ankle fracture with split-thickness skin graft to surrounding avulsion injury.
Latissimus Dorsi Muscle Free Flap
The latissimus dorsi muscle free flap is a predictable, reliable, and adaptable option for the reconstructive surgeon.55,58
This flap is large and is relatively easy to harvest with predictable, large diameter vessels. The flap is based on the thoracodorsal artery, which is a branch of the subscapular artery, and has a length of 6.0 to 11.5 cm from its branch-off of the subscapular artery to its entrance into the muscle (). The thoracodorsal is a large artery that has only one large vena comitans. Immediately on entering the muscle, it splits into medial and lateral branches. The flap can be made bilobed, based on the medial and lateral branches of the thoracodorsal artery, augmenting its ability to resurface complex wounds. The thoracodorsal nerve travels with the artery and vein, and must be dissected and ligated, unless only a partial flap is raised and some residual functional muscle is intended. In its course the thoracodorsal artery typically gives rise to 2 arteries, which must be ligated: the angular artery to the lateral border of the scapula and a branch to the serratus anterior muscle. There is some variability in the origin of these arteries, however. The entire muscle typically will survive off of the thoracodorsal artery and vena comitans. However, the distal margins of the flap are also supplied segmentally by intercostals and lumbar arteries, and occasionally necrosis of the distal edges of the flap occurs.
Fig. 14 Vascular pedicle of the latissimus dorsi muscle flap. 1, latissimus dorsi muscle; 2, searratus anterior muscle; 3, teres major muscle; 6, axillary artery and vein; 7, subscapular artery and vein; 8, thoracodorsal artery, vein, and nerve; 9, circumflex (more ...)
Patients have minimal deficit after harvesting of the latissimus dorsi because of the compensatory action of adjacent muscles; namely, the pectoralis major and the teres major. The latissimus dorsi muscle itself can measure up to 40 cm in length and 20 cm in width, and have a thickness of about 0.8 cm. Combining the length of the pedicle and the length of the muscle itself, the overall reach of the latissimus dorsi muscle free flap can be over 40 cm, which can be a distinct benefit when a wide zone of injury needs to be traversed to obtain coverage of a foot and ankle. A skin paddle up to 20 cm in width and 40 cm in length can be raised with the muscle. Any skin paddle wider than 10 cm will likely need secondary skin grafting of the donor site. The skin paddle will have significant excursion and mobility relative to the underlying latissimus muscle, which may result in ulceration with shoe wear and if it is used on weight-bearing surfaces. Furthermore, because of its multisegmental cutaneous sensory innervation, it is not possible to obtain sensate coverage with this flap. Also, the adipose layer is often thick in this area, and results in a bulky flap. If such circumstances are a concern, then a split- or full-thickness skin graft placed over the muscle may be a better, more durable choice than lifting a skin paddle with the graft. However, even if later excised and skin grafted, a small skin paddle can be lifted with the muscle flap for the purpose of flap monitoring, as it is simpler to monitor a skin paddle than muscle.
To avoid a skin contracture across the shoulder joint, the surgeon should not incise into the axillary skin. The pedicle may be developed by elevating and dissecting under the axillary skin. If an incision into the axillary skin is necessary to safely develop the pedicle, a zig-zag incision is recommended. Two to 3 large round drains are placed in the harvest site, sutured to the skin, and placed on bulb suction. To minimize seroma formation at the donor site, the drains are kept in place until the drainage is less than 10 mL per 8-hour shift per drain for 4 consecutive shifts.
A relative drawback of the latissimus dorsi muscle free flap is the challenge that arises in patient positioning for the procedure. The patient must be positioned in such a way to permit a technically sound microvascular anastomosis. This procedure must be accomplished without sacrificing access to the recipient wound so the flap can be properly inset. Both of these need to be performed while placing the patient in as close as possible to a lateral decubitus or prone position to allow harvesting of the latissimus flap. The surgeon should also consider that the lateral decubitus position may be physiologically disadvantageous in the multi-injured patient.
Rectus Abdominis Muscle Free Flap
The rectus abdominis muscle free flap is also a reliable and predictable flap.55,59
Either the deep superior or deep inferior epigastric artery can be used to supply the free tissue transfer. The deep inferior epigastric artery, arising from the external iliac artery, is generally chosen for free-tissue transfer because it is larger and longer, and it provides a more favorable network of perforators to the skin, should a myocutaneous flap be fashioned. The deep inferior epigastric artery provides a pedicle length ranging from 7.1 to 14.7 cm and its diameter is approximately 2 mm (). This artery has 2 venae comitantes. Just as the latissimus dorsi myocutaneous flap has multisegmental cutaneous sensory innervation, the skin over the rectus musculature is segmentally innervated by the intercostal nerves. However, it also has segmental motor innervation so the flap can neither maintain motor function nor be sensate. The average dimensions of this flap are 30 cm in length, 6 cm in width, and 0.6 cm in thickness. The dimensions of this flap have obvious implications with respect to utility compared with the latissimus dorsi muscle flap. The effective reach of the flap is sizeable, yet not as great as the latissimus dorsi muscle flap. If great length is needed to reach a site of microanastomosis out of the zone of injury, either the latissimus dorsi muscle free flap or the rectus abdominis muscle free flap may satisfy. However, when there is a large zone of injury that must be spanned, yet the remote wound is relatively small, then the breadth of tissue supplied to the target by the latissimus dorsi muscle free flap may be more than needed; in these cases the rectus abdominis muscle free flap may be more suitable.
Fig. 15 Vascular pedicle of the rectus abdominis muscle flap. 1, posterior layer of the rectus sheath; 2, rectus abdominis; 3, inferior epigastric vessels; 4, anterior layer of rectus sheath; 5, superior epigastric vessels, ligated. (From Masquelet AC, Gilbert (more ...)
The function of the rectus abdominis musculature is to flex the vertebral column and to supply strength to the abdominal wall. Morbidities of harvesting this muscle are potential weakness of trunk flexion and abdominal herniation. The patient frequently has significant reservations to the procedure because of the misperception that a cosmetic deficit of losing “half of their 6-pack abs” will result. A significant relative advantage of the flap is the ease of patient positioning and harvesting.