Midface Reconstruction





Introduction


Reconstruction of the midface, particularly of the maxilla, following tumor removal is a significant challenge because of its complex three-dimensional architecture and important role in facial esthetics and function. The goals of reconstruction include: (1) maintaining midfacial height, width, and projection; (2) creating a stable platform for mastication and dental restoration; (3) separating the oral cavity from the nasal cavity; (4) preserving a patent nasal airway; (5) supporting the soft tissues of the face, including the nose, lips, cheeks, and eyelids; and (5) restoring the bony orbit to avoid changes in orbital volume and globe position that may result in eye exposure or impaired vision, or provide stable wound closure for the exenterated orbit.


In the past, maxillary reconstruction mainly involved prosthetic obturation. This option results in immediate dental restoration without further surgery but, in larger defects, as well as in cases where radiation-associated tissue contracture occurs, instability, poor retention, and oronasal leakage of air, liquid, and food may occur. Furthermore, results of prosthetic obturation are disappointing or unacceptable in extensive midfacial defects, such as those that involve the orbital floor. The advent of microsurgery has permitted primary single-stage reconstruction of these complex facial defects, avoiding the use of a prosthesis as well as various combinations of local and regional flaps that have poorer esthetic and functional results and higher complication rates.


Reconstructive Approach


One of the biggest challenges associated with reconstructing the maxilla is that the defects created by oncologic resection are highly variable. Several classification systems have been proposed, each with its strengths and weaknesses. According to Archibald et al, the ideal maxillary treatment algorithm should “use a functional approach that defines the defect-related challenges, prioritizes the reconstructive goals, and identifies how and to what extent each of the microsurgical free flaps could meet these goals.” Therefore, rather than memorizing a specific classification system, it is more important to understand the critical structures that need to be addressed during the reconstruction and base the surgical approach on these needs. These structures include: the palate and alveolus, the orbital floor, and the orbital contents. , This chapter will examine each of these areas.


Reconstruction of the Palate and Alveolus


Posterior Defects


Palatoalveolar defects that are unilateral and posterior to the canine tooth are well suited to reconstruction by a number of techniques. Prosthetic obturation can give excellent results for such defects. , The obturator is stabilized by both canine teeth, which have very long, stable roots, and the contralateral molars. An obturator is usually the simplest solution for these defects, requiring no further surgery, and, therefore, no donor site morbidity ( Fig. 25.1 ). The maxillectomy wound is either packed or a temporary prosthesis is placed and secured to the wound. Once healed, an obturator is fabricated by a maxillofacial prosthodontist. Another advantage of obturation is that the maxillectomy cavity can be inspected for local cancer recurrence under direct vision by removal of the prosthesis. However, some patients experience problems with fit causing leakage of foods and liquids during eating or air during speech production due to tissue contracture, particularly those who have been irradiated. Periodic refitting and replacement is also required for the life of the patient, which is another relative disadvantage.




Fig. 25.1


Examples of palatal obturator prostheses. (A) Obturator created for a large right hemimaxillectomy defect, stabilized with adhesive to the remaining edentulous left maxilla. (B) Obturator created for a smaller left posterior palatoalveolar maxillary defect, stabilized using clasps that hook around the remaining teeth.


Posterior palatoalveolar defects can also be reconstructed with various autologous tissue flaps. The temporalis muscle pedicled flap can be transposed into the oral cavity to reconstruct these defects. , The muscle is harvested using a hemicoronal incision and removal of the mandibular condyle facilitates transposition into the oral cavity. The main disadvantage of this technique is that it often leaves a noticeable donor site depression, although this can be minimized by leaving the anterior one-third to one-half of the muscle in situ or by placing an implant (e.g., porous polyethylene) or filler (e.g., delayed autologous fat grafting) in the donor site. The temporalis muscle can also be used to reconstruct midpalatal defects that do not involve the alveolus at all.


The majority of posterior palatomaxillary defects in the author’s practice are reconstructed with soft tissue free flaps. Bony free flaps are also suitable but do not offer significant advantages for most patients, unless osseointegrated implants for dental restoration are desired. Most patients that are referred for flap reconstruction have rejected the idea of an obturator or have tried one and been unsatisfied. The anterolateral thigh (ALT) flap, rectus abdominis myocutaneous (RAM) flap, and radial forearm fasciocutaneous free flap (RFFF) have been most frequently described for soft tissue reconstruction of posterior palatoalveolar defects. , , , The ALT free flap is most commonly selected in the author’s practice because of its long pedicle, minimal donor site morbidity, and ability to adjust flap thickness by inclusion of vastus lateralis muscle to increase thickness or microdissection to thin the flap ( Fig. 25.2 ). The RAM flap is often excessively thick in most patients, while the RFFF is usually avoided because it is thin and does not obliterate the maxillary sinus, creating an air space superior and inferior to the flap, theoretically raising the risk for fistula formation.




Fig. 25.2


(A) A left posterior palatoalveolar defect. (B) An anterolateral thigh (ALT) free flap after dissection, measuring approximately 5×5 cm. (C) Postoperative appearance several months following reconstruction with the ALT free flap.


The pedicle of the flap is tunneled from the oral cavity to the neck where a microvascular anastomosis is performed to the facial artery and vein, which are exposed with a short incision made 1–2 fingerbreadths below the inferior border of the mandible. When creating this tunnel, care is taken not to divide the parotid duct as a hole is made in the buccinator muscle and a 2–3 fingerbreadth-wide subcutaneous pathway to the recipient vessels is dissected. Alternately, the superficial temporal vessels can be used as recipient vessels. The ideal reconstruction is level with the remainder of the hard palate or slightly higher. This allows space for a prosthesis for dental restoration if the patient later desires one. A bulky or ptotic flap does not permit fitting of a dental prosthesis.


Hemipalatoalveolar Defects


A number of techniques have been advocated for maxillary defects that involve around half of the palate and alveolus. At many centers, patients are treated with a prosthetic obturator for these defects. The difficulty with obturators for hemipalatoalveolar defects is that there is a limited amount of teeth and alveolar arch to create stable fixation of the prosthesis. Metal clasps used for fixation of the prosthesis can eventually cause loosening of teeth because of the high torque forces exerted when masticating with an unstable obturator. Soft tissue contracture around the obturator can also cause distortion of the facial features, such as elevation of the upper lip and deviation of the nose toward the side of the defect. Fewer patients can be successfully treated with an obturator following hemipalatomaxillectomy than posterior maxillectomy. ,


Some authors have advocated soft tissue free flap reconstruction, for example with a RAM free flap. , This flap is a highly reliable flap and will create a watertight seal between the oral and nasal cavities. The bulk of the flap is used to restore the shape of the cheek. However, in the author’s experience, soft tissue flaps tend to contract and descend with time, particularly when postoperative radiation is given. This can result in unilateral loss of midfacial projection and facial symmetry. Additionally, the nose will start to deviate toward the side of the maxillectomy unless the portion of the maxilla adjacent to the external nose (sometimes referred to as the piriform rim) is preserved. Retention of a dental prosthesis following soft tissue reconstruction tends to not be stable for the same reasons obturators are often unstable.


The radial forearm osteocutaneous, scapula, iliac crest, and fibula free flaps have all been proposed for bony reconstruction of hemipalatomaxillectomy defects. The bone portion of the radial forearm osteocutaneous flap is osteotomized and rigidly fixed with titanium miniplates to reconstruct the alveolar arch, restoring anterior maxillary projection. , The skin paddle is used to reconstruct the oral palatal side and can be wrapped around the bone so that there is a skin paddle on the nasal side, de-epithelializing the intervening skin to which the lip is attached (so-called “radial forearm sandwich flap”).


The scapula is also a popular choice for hemimaxillectomy reconstruction. In most descriptions the scapular bone, either perfused by the circumflex scapular artery or the angular branch of the thoracodorsal artery, is oriented such that the flat surface lies roughly in the coronal plane and the relatively lateral edge of the scapular bone rests inferiorly. One problem with this orientation is that it may be difficult to accurately restore the subtle nuances in maxillary shape. However, the lateral edge of the bone is often, though not always, thick enough to accommodate placement of osseointegrated implants for dental restoration. The bone can also be oriented transversely, taking advantage of the triangular shape of the scapular tip (scapular angle) to restore anterior maxillary projection, though the bone is usually not thick enough for osseointegrated implant placement in this orientation and rigid fixation is more challenging.


The iliac crest free flap, based on the deep circumflex iliac artery, in contrast provides ample thickness and height for osseointegrated implant placement. , The thick cortex of the bone also helps with implant retention, compared to the scapula, which tends to have a thin cortex and proportionately more medullary bone. In most cases, the bone is oriented vertically so that the flat surface faces roughly coronally, where the anterior maxillary wall was previously. The difficulty with the iliac crest is that, in many patients, the skin paddle is very thick and requires revision surgery for debulking. A very bulky flap can occlude the airway and require prolonged tracheostomy use. Alternately, the internal oblique muscle can be used to close the palatal defect, requiring either skin grafting of the muscle surface or allowing muscle to mucosalize spontaneously, or a thin fasciocutaneous free flap, such as the RFFF, can be used in combination with the iliac crest bone.


The author’s preferred method for reconstruction following hemipalatomaxillectomy is to use the fibula osteocutaneous free flap. , The fibula osteocutaneous flap has a thin skin paddle such that most patients are not at risk for airway occlusion when that skin paddle is used to restore the palatal mucosa. The main advantages, however, are the long length of bone that can be osteotomized to mimic the complex shape of the maxilla and the height and width of the bone that make it a good substrate for placement of osseointegrated implants. Also, because the donor site is distant from the head, simultaneous flap harvest and bone shaping can be performed with the maxillary resection, saving considerable operative time.


The ipsilateral fibula is typically used for maxillectomy defects to orient the lateral surface of the fibula superficially for titanium plate fixation and the skin paddle inferiorly to reconstruct the palate while the pedicle of the flap comes to lie posteriorly and laterally ( Fig. 25.3 ). A small amount of muscle is left adherent to the bone and the nasal surface is allowed to mucosalize spontaneously. If the resection is extended to include the malar eminence of the maxilla (superior portion of the maxilla), an additional segment of bone is used to restore this area. The mean height of the lateral surface of the fibula is approximately 18 mm, which roughly corresponds to the height of the premaxilla (mean of 20 mm) and the malar bones (mean of 22 mm). Because the premaxilla is inferior to the malar bones in the cranial–caudal dimension, the bones need to be offset from each other, either by angling a “single-barrel” reconstruction ( Fig. 25.4 ) downward or positioning the fibular segments in a “double-barrel” configuration ( Fig. 25.5 ). The facial or superficial temporal blood vessels are used as recipient blood vessels. Vein grafts are commonly needed to reach the recipient blood vessels.




Fig. 25.3


(A) A left hemimaxillectomy defect, that extends to the midline. (B) Reconstruction of the hemimaxillectomy defect with a fibula osteocutaneous free flap. The fibula height is very close to the height of maxillary bone in the malar region as well as the height of the premaxilla. The fibula skin paddle is used to close the palatal mucosal defect. (C) Postoperative appearance demonstrating excellent facial symmetry.

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May 23, 2021 | Posted by in General Surgery | Comments Off on Midface Reconstruction
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