By Timothy Thomason, M.D. 
One of the most important advances in reconstructive surgery for head and neck cancer has been the development of techniques for microvascular tissue transfer. This technique involves harvesting flaps of healthy tissue with their blood supply from remote sites in the body and implanting the tissue in the recipient wound bed. The blood vessels associated with the donor graft are anastomosed with recipient vessels in the wound bed. The first reported free tissue transfer was vascularized jejunum performed by Siedenberg in 1959. Panje performed the first free flap for oropharyngeal reconstruction in 1976. The fibula free flap was used for mandible reconstruction by Hidalgo in 1989. Today the most common free flaps in head and neck reconstruction are the radial forearm, the rectus abdominis, and the fibula. Other important flaps include the anterolateral thigh, latissimus dorsi, scapula, and the iliac crest.
There are numerous advantages with free tissue transfer compared with traditional pedicled flaps or non-vascularized grafts for reconstructive surgery. A wide variety of tissue types including skin, muscle, fascia, and bone are available for transfer. Large bulky flaps may be used for large defects and thin pliable flaps for smaller defects. The variety of tissue type and size allows for optimization of function and cosmesis. A second surgical team can often harvest the donor flap at the same time as the cancer resection. The vascularized tissue tolerates post-operative radiation. Also, if the patient has already had radiation in the head and neck region then non-radiated donor tissue can be moved into the recipient wound bed. Because the vessels may be re-connected with any suitable-sized recipient vessels, numerous spatial orientations are possible for the donor flap. Another big advantage for vascularized bone flaps is the possibility of later acquiring osseointegrated dental implants. Although the operative times are longer with microvascular reconstruction, there is usually no need to stage procedures. Finally, the success rates for free flaps are generally greater than 90%. Disadvantages with this technique include longer operative times, the requirement of significant technical expertise, and donor site morbidity. Nevertheless, free flaps should be considered in many patients with significant defects after cancer resection in the head and neck. This discussion will focus on the radial forearm, rectus abdominis, fibula, and anterolateral thigh free flaps.
General Considerations
Once a flap is removed from the donor site, the insetting of the flap begins. If the flap contains an epithelial surface then interrupted horizontal mattress sutures are used for re-approximation with recipient tissue. The orientation and position of the flap should allow for a tension-free vascular anastomosis without any kinking of the vessels. Recipient vessels should be identified during the cancer resection. The facial artery is often used for reconstructions involving the oral cavity or pharynx. Other branches of the external carotid may also be used if necessary. The recipient vein(s) may be the internal jugular (end-to-side) or external jugular (end-to-end) veins. Use of an operating microscope is necessary for the vascular anastomosis. A microvascular set is used that contains non-traumatic vessel clamps, jeweler's forceps, microvascular scissors, vessel dilators, and a microvascular needle driver. Either the artery or the vein may be done first depending on the surgeon's preference. First, the adventitia is removed from the ends of the vessels. Then, the lumen of the vessel is dilated and irrigated with heparinized saline to remove any clots. The anastomis is performed with simple interrupted 9-0 nylon sutures. The vascular clamps are released and the flap is examined for adequacy of perfusion. Papaverine may be sprayed on the pedicle after anastomosis to help with vasodilation. Drain placement and closure of the incisions must be done without traumatizing the vessels. A Doppler is used after release of the vascular clamps and a corresponding place on the skin is marked with a suture. The Doppler signal should be identified through the skin after all incisions are closed.
Free flaps require long operative times so patients with significant co-morbidities may not be suitable candidates for these procedures. The flaps must be monitored closely for signs of ischemia after surgery. Arterial insufficiency will result in a pale, cold flap without a detectable Doppler signal. Venous insufficiency will result in an edematous, purple-appearing flap that may have a detectable Doppler signal. In either case, the flap may not survive unless the condition is reversed. In such a situation, the patient should be promptly taken back to the operating room for exploration of the pedicle. Simple measures to improve perfusion post-operatively include treating anemia with transfusion, avoiding use of vasopressors, and keeping the flap warm with a warming blanket. Usually, patients are kept in intensive care units for a minimum of two days after surgery. The flap should be checked by a physician or ICU nurse every hour for at least twenty-four hours after surgery.
Radial Forearm Free Flap
The radial forearm free flap (RFFF) allows for the transfer of a large amount of thin, pliable, well-vascularized skin. This flap was first described by Yang, et al, in China in 1981 (1). It is most often harvested as a fasciocutaneous flap although a section of radial bone may be harvested with it as well. The RFFF is excellent for reconstruction of oral cavity, oropharyngeal, and hypopharyngeal defects, such as those found after hemiglossectomy or laryngectomy with partial pharyngectomy (see Figures 1-4). The RFFF may be fashioned into a tube for total pharyngoesophageal defects (Figures 5, 6). Another common use is for reconstruction of total or subtotal lower lip defects. Advantages with this flap include the large amount of thin, pliable skin that is available. The flap is relatively easy to raise and has reliable vasculature. Disadvantages include the need for a split-thickness skin graft and the unsatisfactory appearance of the forearm scar.
The flap should be taken from the non-dominant hand and a pre-operative Allen's test is necessary to establish the presence of adequate collateral blood supply to the hand. It is best to avoid any needle sticks or blood pressure measurements on the donor site arm before surgery. The arm is prepped and a tourniquet is applied to the upper arm. The approximate size of the defect is measured and a rectangular flap is outlined on the anterior-lateral surface of the forearm. This flap should be centered over the course of the radial artery. The radial artery with its two vena comitantes comprise the vascular pedicle for this flap. The cephalic vein may also be incorporated if more than one venous anastomosis is desired. The lateral antebrachial cutaneous nerve may be used to provide a sensate flap. The incision is extended towards the cubital fossa for exposure of the vessels. The incisions are carried down through the fascia overlying the forearm muscles on all sides of the rectangular flap except the proximal side. The vessels are located distally and ligated. Care must be taken to avoid injury to the superficial branch of the radial nerve to prevent dorsal hand numbness post-operatively. The flap is raised in a sub-fascial plane. The vascular pedicle with its septocutaneous perforators are identified between the bellies of the brachioradialis and flexor carpi radialis muscles. The pedicle is dissected in a distal to proximal direction to the origin of the radial artery as the brachial artery bifurcates into the radial and ulnar arteries. It is important to leave the paratenon intact to provide suitable tissue for skin grafting. The wound is closed with a split-thickness skin graft and a splint is placed on the forearm for protection.
Rectus Abdominis Free Flap
The rectus abdominis flap was originally used as a pedicled flap for breast reconstruction. However, with the advent of microsurgical techniques the flap has become quite useful as a free flap for reconstruction in the head and neck. The rectus abdominis free flap (RAFF) provides a large amount of muscle and skin for reconstruction of large defects. A second surgical team can harvest the flap with the patient in the supine position at the same time as the cancer resection. It is excellent for reconstruction after lateral temporal bone resection, total glossectomy (Figures 7, 8), or maxillectomy with orbital exteneration. Advantages for this flap include reliable large caliber vessels and the large amount of bulk that is available for transfer. Also, the donor site can almost always be closed primarily without the need for a skin graft. One disadvantage is the possibility of later developing an abdominal hernia at the donor site.
The flap is usually taken as a fusiform flap in the paramedian position. Prior inguinal surgery is a contraindication for this flap. The size of the defect is measured and the appropriately sized flap is marked on the abdomen. The flap should include the periunbilical skin as this area contains important perforators that provide axial blood supply to a large amount of abdominal skin. The incisions are carried down through skin and subcutaneous tissue. The linea alba and linea semilunaris are medial and lateral landmarks, respectively. The inferior deep epigastric artery and vein comprise the vascular pedicle for the flap. The vessels are identified on the deep surface of the rectus abdominis muscle. The flap is raised in a superior to inferior direction and the vessels are dissected out to their origin off the external iliac artery and vein. The posterior rectus sheath should be left intact. The anterior rectus should should be closed primarily or with mesh to prevent a ventral hernia. A suction drain is left in the wound to prevent hematoma.
Fibula Free Flap
The fibula free flap was first used for mandible reconstruction by Hidalgo in 1989 (2). It is the most common free flap for mandible reconstruction today. The flap provides up to twenty-five centimeters of vascularized bone with or without a skin paddle. The vascular pedicle includes the peroneal artery and vein. Preoperative imaging of the vessels of the lower extremity is indicated to identify those patients who have insufficient collateral blood supply to the foot. If the patient's blood supply to the foot is dominated by the peroneal artery then a FFF from that leg is contraindicated. If neither leg has sufficient vessels then another bone flap, such as the iliac crest flap, should be used. The FFF is popular for several reasons. It can be harvested by a second surgical team. It provides a long segment of bone that can actually be cut into smaller segments to re-create curvature of the mandible. Osseo-integrated dental implants can often be placed post-operatively. Disadvantages include the somewhat tenuous blood supply of the skin paddle and the need for a skin graft to close the donor site if a skin paddle is harvested.
The flap may be taken as an osteocutaneous flap or simply a bone flap without skin. Figures 9 and 10 show a CT scan and surgical specimen of a neuroblastoma involving the mandible in a child. Figures 11 and 12 show the harvested fibula flap on a titanium reconstruction bar. To raise the flap, first the head of the fibula and the lateral malleolus are identified and a line is drawn between them. If skin is to be harvested then perforators are identified with a Doppler 15-25 cm distal to the fibula head. The skin paddle should include several identifiable perforators for the best result. The incision is made at the anterior edge of the skin paddle and extends superiorly towards the fibula head for exposure of the pedicle. The incision is carried down through the fascia of the peroneus muscles. These muscles are then retracted anteriorly and the dissection continues to expose the intermuscular septum. This septum divides the peroneus longus and soleus muscles and attaches to the lateral surface of the fibula. Cutaneous perforators are usually located within this septum. Next, the incisions is made along the posterior border of the flap and carried down through the fascia overlying the soleus muscle. The soleus muscle is then retracted posterioly and dissection proceeds towards the intermuscular septum from the posterior side. If no perforators were identified from the anterior side then a one-centimeter cuff of soleus muscle should be taken with the flap so that any musculocutaneous perforators can be saved.
At this point, bone cuts should be made. The proximal bone cut should be no less than 6 cm from the fibular head to insure that the peroneal nerve is not injured. Distally, the cut should be made at least 8-10 cm above the lateral malleolus to prevent instability in the ankle joint. After the bony cuts are made the segment of fibula will be more mobile. The bone is then rotated posteriorly to expose the attachments of the peroneus longus and brevis muscles. These muscle attachments on the fibula are divided, leaving a 2-3 mm cuff of muscle on the bone so that periosteum is not injured. This exposes the anterior intermuscular septum which is then divided in a similar fashion. Next, the attachments of the extensor digitorum, extensor hallucis longus, and tibialis anterior are separated from the fibula in the same manner. This will expose the interosseous membrane, which is then divided 2-3 mm from the fibula. This will expose the tibialis posterior muscle. The peroneal vessels will be just posterior to the tibialis posterior muscle. Next, the peroneal vessels are identified at the site of the distal osteotomy and ligated. The flap is raised from a distal to proximal direction with careful identification of the peroneal vessels as well as protection of the posterior tibial vessels. The attachments of the tibialis posterior are divided as the peroneal vessels are traced proximally towards the bifurcation of the peroneal and posterior tibial vessels. The last muscles attachments are from the flexor hallucis longus and brevis muscles. These are divided with direction visualization of the pedicle. The pedicle may be left intact while the contouring of the reconstruction plate and any other fibula osteotomies are performed. The pedicle vessels are ligated when the flap is ready to be inset in the recipient site. The wound is closed with a skin graft over the site from which the skin paddle was harvested. The remaining incisions are closed primarily with a suction drain in place. A lower leg splint is left in place for five days.
Post-operatively, the flap should be closely monitored for signs of vascular insufficiency. If the skin paddle appears well-vascularized then the underlying bone is assuredly well-perfused as well. If the skin paddle is not well-perfused, it may be due to poor cutaneous perforators and the underlying bone may be well-perfused. A nuclear medicine bone scan can determine the state of perfusion of the bone if necessary. The patient should ambulate in a non-weight bearing fashion as soon as possible. Weight-bearing should begin when the splint is removed on post-operative day number five.
Anterolateral Thigh Free Flap
The anterolateral thigh free flap (ALTFF) was described in China by Song, et al, in 1984 (3) and used for head and neck reconstruction by Koshima, et al, in 1993 (4). The flap is based on the descending brach of the lateral circumflex femoral artery and its two vena comitantes. The ALTFF provides a large amount of skin and a variable amount of muscle. The thickness of the flap is intermediate between the RFFF and RAFF and is variable depending on how much vastus lateralis is taken with the flap. Thicker flaps may be used for total glossectomy or lateral temporal bone defects (see Figures 13-16). Thinner flaps are well-suited for oropharyngeal or hypopharyngeal reconstruction. Advantages of the ALTFF include its versatility, large caliber vessels, and low donor site morbidity.
The flap is contra-indicated in patients with prior injury or surgery in the region of the upper thigh. The entire leg should be prepped and draped. Like the free flaps discussed above, a second surgical team may harvest the flap at the same time as the cancer resection. The anterior-superior iliac spine and lateral border of the patella are marked and a line is drawn between these two points. The midpoint of this line is measured and a circle with a three-centimeter radius is drawn around this point. Next, a Doppler is used to locate cutaneous perforators within this circle. At least three perforators should be identified. The flap design should incorporate the circle with these perforators. The size of the defect is measured and the flap is designed to match this size. Usually, the flap is designed as a fusiform flap with the long axis centered on the line between the anterior-superior iliac spine and the lateral border of the patella.
The incision is made at the anterior border of the flap and carried down through the fascia of the rectus femoris muscle. Subfascial dissection is continued laterally towards the intermuscular septum between the rectus femoris and vastus lateralis muscles. At this point the vascular pedicle should be identified. The lateral circumflex femoral arterty branches off the common femoral artery and divides into ascending, descending, and transverse branches. Usually, the cutaneous perforator(s) will originate from the descending branch although occasionally they will come from the transverse branch. Sixty percent of patients will have musculocutaneous perforators that pass through the vastus lateralis. The remainder of patients will have septocutaneous perforators that pass through the intermuscular septum between the vastus lateralis and rectus femoris. After suitable vessels are identified the lateral incision can be made through skin and fascia latae. If musculocutaneous perforators were present then a cuff of vastus lateralis should be taken with these perforators. At least one perforator is necessary for flap survival. The pedicle vessels are then dissected proximally to the origin of the descending branch (or less commonly the transverse branch). Muscular branches of the pedicle vessels should be carefully ligated to prevent post-operative bleeding. Care must be taken to avoid injury to the femoral nerve that innervates the vastus lateralis. The donor site can usually be closed primarily unless a very large flap was taken, in which case a skin graft is needed. A suction drain is placed in the wound bed prior to closure. The patient should have full weight-bearing status on post-operative day one.
Summary
Free flaps have become indispensable for reconstruction of complex defects after cancer resection in the head and neck. Their versatility in terms of size and tissue type allows for optimal function and appearance. Success rates are high for these procedures, although they do require microvascular expertise, longer operative times, and intensive post-operative care. Nevertheless, free flaps will continue to be important tools for the reconstructive surgeon in the region of the head and neck.
References
1) Yang G, Chen B, Gao Y and others: Forearm free skin flap transplantation [in Chinese], Natl Med J China 61:139, 1981.
2) Hidalgo DA. Fibula free flap: a new method of mandible reconstruction.
Plast Reconstr Surg. 1989 Jul;84(1):71-9.
3) Song YG, Chen GZ, Song YL: The free thigh flap: A new free flap concept based on the septocutaneous artery. Plast Reconstr Surg 1984; 37: 149.
4) Koshima Koshima I, Fukuda H, Yamamoto H: Free anterolateral thigh flaps for reconstruction of head and neck defects. Plast Reconstr Surg 1993; 92: 421-430.
Free flap descriptions were taken in large part from the following sources:
Bailey, B. Atlas of Head & Neck Surgery-Otolaryngology. Second Edition, 2001. Chapters 276, 278, and 279.
Cumming, C. Otolaryngology-Head & Neck Surgery. Fourth Edition, 2005. Chapter 6.
Winslow CP and Wax MK. Emedicine. Tissue Transfer, Fibula. . Updated March 23, 2006.
Leach JL and Myers LL. Emedicine. Free Tissue Transfer, Lateral Thigh and Anterolateral Thigh. Updated July 15, 2005.
