Reconstructive Surgery: Free Fasciocutaneous Flaps and Bone-Containing Flaps
Free flap reconstruction has become an integral part of the multidisciplinary care of head and neck cancers and the preferred reconstructive technique at many major medical oncology centers to repair complex defects of the head and neck. Current experience demonstrates that microvascular free tissue transfer frequently allows for reliable, single-stage, and immediate reconstruction in this patient population. The success rates for microsurgical procedures have greatly improved over the past few decades. Many centers have reported free flap success rates greater than 96%, and in some expert hands, close to 99%, making this operation one of the most reliable procedures in reconstructive surgery. However, because the use of these flaps permits advanced tumors to be more aggressively treated by surgery in a patient population with a high prevalence of coexisting diseases, complications are not uncommon and flap failures do occasionally occur.
Many aspects of resective surgery should be modified when a microsurgical transfer is anticipated, but once the resection is complete, attention focuses on analysis of the component parts of the defect. The complexities of the methods of reconstruction follow a “reconstructive ladder”, beginning with simple split-thickness skin grafts at one end, proceeding to free tissue transfer at the other. Ascent of this ladder does not always imply a superior result because in the appropriate circumstances, for instance, a skin graft may provide the best functional and cosmetic result. When compared with pedicled locoregional flaps, these procedures prove more complex and demanding in terms of equipment, cost, and surgical experience.
The method of reconstruction with free flaps must be preselected depending upon the estimate size and shape of the defect and the structures involved and what donor site tissue is most appropriate. Thorough preoperative planning should also evaluate potential alternative methods of reconstruction.1
Controversy still exists about whether microvascular reconstruction is functionally superior to pedicled reconstruction of comparable defects. Intuition suggests that revascularized free-tissue transfer is functionally superior because it allows the reconstructive surgeon to customize reconstruction of defects of the head and neck. Free flaps can be designed to provide epithelium, subcutaneous tissue, muscle, and bone in proportions that closely resemble the missing tissue.2
Despite the best preoperative care, meticulous surgical technique, and attentive postoperative management, complications frequently arise in the patient with head and neck cancer. Many of these individuals are elderly with concomitant medical problems and pose a constant challenge for those involved in their care. About 20% of the patients will have perioperative medical complications, with pulmonary, cardiac, and infectious complications predominating,3 and with multiple complications occurring in 10%.4 Most of the medical literature suggests that comorbidity is likely to be the most important factor in determining the risk of perioperative complications. Early recognition of the symptoms and signs of complications can prevent amplification of existing problems. However, a perioperative mortality of 1 to 3% must be expected.
In some series, age remained a statistically significant predictor of medical complications,3,4 but other investigators have concluded that age should not be considered when deciding whether a patient is an acceptable candidate to undergo a free flap reconstruction. Previous radiotherapy could increase the rate of complications for some authors but it is not a contraindication for free flaps.
The purpose of this chapter is to focus on the major surgical complications in free flap reconstructions and how they are best avoided or treated once they occur. It is beyond the scope of this chapter to review specific complications such as fistulas, dehiscences, or stenosis, because they do not only occur in free flaps and are usually multifactorial.
Fasciocutaneous flaps are tissue flaps that include skin, subcutaneous tissue, and the underlying fascia. Circulation to a fasciocutaneous flap is based on the prefascial and subfascial plexuses. They can be raised without skin and in some cases can include bone tissue.
Fasciocutaneous free flaps are gaining widespread popularity for the reconstruction of head and neck defects and in many units these flaps are used in preference to enteric free flaps (jejunum, omentum), especially in pharyngolaryngoesophageal reconstructions. This popularity is mainly because of the low donor site morbidity compared with the potential complications following opening the abdominal cavity.
Many different fasciocutaneous free flaps have been described for head and neck reconstruction. In this chapter we will focus mainly on the most widely used, such as the radial forearm, the anterolateral thigh, the scapular–parascapular, and the fibular osseocutaneous free flaps. Others free flaps that are much less used will not be reviewed, such as the ulnar forearm, lateral arm, lateral thigh, rectus abdominis, or osseocutaneous such as iliac crest.
The subject of this chapter is reviewing surgical complications in fasciocutaneous and osseocutaneous free flap reconstructions in head and neck as follows:
Complications at donor site
Complications at receiving site
Free flap failure
– Causes for free flap necrosis
– Microvascular technique and recipient vessels
– Managing flap failure
– Salvage reconstruction following flap loss.
Complications at Donor Site
The selection of donor tissues should first meet the needs of the defect. Beyond that, when the other choices are equal, the donor site morbidity should be kept to a minimum. Attention should be given to the donor site in terms of aesthetics and functional morbidity. Potential donor site sequelae and complications must be evaluated and taken into account in thorough preoperative planning.
Radial Forearm Flap
In the case of the radial forearm flap donor site morbidities are generally minor. The worst complication is the unrecognized lack of crossover circulation between the volar and palmar arches. This situation, seen in ~ 15% of the patients, must be identified preoperatively by the Allen test. If ulnar perfusion is inadequate, an alternative flap must be formed. In the rare event that this flap has to be chosen despite this anatomical variant, then reconstruction of the radial artery is mandatory.
When the distal radius is used as an osseous donor site, the complication of forearm fracture must be prevented with an adequate technique of osteotomy. When bony defects larger than ~ 10 cm are anticipated, reconstruction may require another free flap (i.e., fibula) or other reconstructive procedure.
Skin grafts are required to cover the donor site defect in the majority of patients so other potential complications are delayed healing of the skin graft, hypertrophic scar formation, sensory nerve damage, or minor functional deficits ( Fig. 29.1 ). To prevent exposure, adhesions, or even rupture of the superficialis dissected tendons, peritenon should be preserved.
Another possibility is the closure of the radial forearm free flap donor site defect with an ulnar rotation-advancement flap that can avoid problems of delayed healing, tendon adhesion, and wrist stiffness ( Figs. 29.2 and 29.3 ). However, the procedure required significant skin mobilization with the potential disadvantages of denervation of the volar forearm and temporary lymphedema.
Anterolateral Thigh Flap
The anterolateral thigh flap has become one of the preferred free flaps in the head and neck because of its minimal donor site morbidity. Scars on the thigh are well accepted, even if skin grafting is needed (rarely) ( Fig. 29.4 ). Contraindications to harvesting the anterolateral thigh flap include previous surgery or injury to the upper thigh compromising the pedicle. Morbid obesity may make the flap too thick and compromise the vascularity. In hypopharynx reconstruction, our experience is that the anterolateral thigh flap seems to have a lower fistula rate even than the radial forearm flap.
Scapular/Parascapular Free Flap
The scapular/parascapular free flap even as osseocutaneous flap has proven to be excellent as a donor site.1 The exception is when very large skin flaps are required, so that the skin graft closure needed leaves a poor donor site. The harvest of the scapular bone usually has no problems and decreased shoulder mobility can be avoided with a proper postoperative physical therapy. To prevent seromas, suction drains must be placed for several days.
Fibula Free Flap
Fibula free flap harvest is associated with a high rate of complications. Abnormalities of the lower leg vascular anatomy may preclude safe harvest of the fibula. Patients with peroneus magnus or impaired circulation to the leg should not undergo fibula transposition.
Caution is advised in patients who have had extensive leg trauma or surgery before planning fibular surgery. Patients who are diabetic and have significant venous stasis or peripheral edema, poor circulation or healing, or cutaneous ulcers are poor candidates for this type of flap and an alternative reconstruction must be evaluated. The skin paddle may not be ideal for intraoral reconstruction because it is rather thick and orientation of the skin on the bone can make reconstruction difficult. Some authors have suggested that skin grafting may result in higher complication rates, because of poor graft take of the donor site wound bed. The peroneal nerve can be damaged during the dissection because it passes around the neck of the fibula. From a functional standpoint, most studies have shown that all or nearly all patients are able to successfully perform their activities of daily living without significant limitations. Reported long-term donor site morbidity has been variable, with some studies reporting no long-term morbidity and others suggesting that the majority of patients experience long-term problems with joint stiffness and instability, muscular weakness, or gait abnormalities. However, complications requiring surgical intervention are rare, and the vast majority of patients have no long-term functional limitations.
Complications at the Receiving Site
Vascular occlusion or pedicle thrombosis remains the primary reason for free flap loss. The majority of flap failures occur within the first 48 hours with venous thrombosis being more common than arterial occlusion. Several authors have investigated the causes and timing of flap failure summarizing venous problems (35 to 80%) as the most common etiology of flap failure followed by arterial problems (30 to 45%), hematoma (20 to 30%), and recipient vessel problems (10%). Late flap failures (i.e., > 48 hours) were most often the result of infection or mechanical stress around the anastomosis. It can be estimated that 15% of patients require a return to the operating theater within 7 days for compromised flap or hematoma.
Free Flap Failure
Loss of vascular perfusion is the main complication associated with free flaps. The irreversible failure of reperfusion through a microvascular anastomosis is termed the “no reflow phenomenon” and has as its basis ischemia and endothelial cell swelling, luminal occlusion, and the release of toxic free radicals with ongoing distal soft tissue damage and necrosis. Free flap failure can lead to functional and cosmetic morbidity, as well as result in additional operative procedures, prolonged hospital stay, and increased health care costs. Moreover, free flap failure in some situations may increase the risk of lethal complications such as rupture of great vessels. All series report a certain incidence of flap failure ranging from 0 to 10%.5 Early detection of flap compromise through careful monitoring and appropriate surgical revision can lead to significant improvements in overall success rates.
Even some authors in a retrospective study, with some bias, try to examine the predictive value of intraoperative physiologic variables in head and neck reconstructive surgeries. The results show that higher intraoperative maximum heart rates are associated with lower rates of mortality and major complications. There were no other independent predictors of morbidity and mortality in their patients.6
Causes for Free Flap Necrosis
There are many different causes for thrombosis or occlusion of the vascular pedicle. Technical errors with flap design and elevation, vessel suturing, tissue handling, or geometry of the pedicle may result in thrombosis. Extrinsic compression of the vascular pedicle by tight wound closure, tapes around the neck, or wound hematoma may also compromise the flap by obstruction of venous out-flow ( Fig. 29.5 ).
When the signs of vascular compromise occur some of the following measures should be immediately undertaken: reposition the patient to relieve possible vascular pedicle compression, remove compressive dressings, release tight sutures, or assess hydration of the patient. If these maneuvers at the bedside are not successful, immediate re-exploration in the operating room is critical.