Successful outcome after surgery should provide the patient with durable locoregional control of the disease and minimal functional deficit. This depends on meticulous planning with accurate mapping of both surface and deep extent of the tumor. The anatomic extent of the surgical defect must be anticipated in all dimensions, and the need for reconstructive effort considered prior to surgery.
The approach chosen must afford good exposure, both for accurate and complete resection of the lesion but also for reconstruction of the defect. Incisions must be planned to provide optimal access while minimizing cosmetic defects. Appropriate modifications may be required when treating indi viduals who have had previous radiation therapy or surgery. The following is a general description of the commonly used approaches to tumors of the oropharynx, but obviously the one used for a particular patient will depend as much on the factors described as the surgeon's individual preference.
Transoral excision may be appropriate for very select, small, superficial cancers with well-defined margins located in the anterior portion of the oropharynx. Early tumors of the tonsils, faucial arches and the soft palate may be safely resected using either diathermy or transoral endoscopic laser, and a discontinuous neck dissection may be combined if indicated.14 The resultant mucosal defect may be closed primarily, skin-grafted or left to epithelialize. All other tumors that require resection of bone, or those that are located more posteriorly, mandate more extensive access.
Anterior (supra- or transhyoid) pharyngo-tomy has been used to approach selected small lesions of the tongue base, posterior pharyngeal wall and for low-grade salivary gland tumors.15 The oropharynx is accessed by either transecting or excising the hyoid bone (transhyoid approach) or displacing it inferiorly (suprahyoid approach) (Figure 6-8). After resection of the tumor inferiorly from the neck, the resultant defect is closed primarily. The main drawbacks of the procedure are that the vallecula is entered blindly and access is very limited.
A lateral pharyngotomy approach may be used for small lesions of the posterior and posterolateral pharyngeal walls. The oropharynx is entered through the mucosa of the superior aspect of the pyriform sinus after carefully retracting the superior laryngeal nerve. Exposure, however, is limited superiorly by the lower border of the mandible, and this approach is applicable in only selected instances.
The anterior midline labiomandibuloglosso-tomy approach (Figure 6-9) may be used to resect locally limited lesions of the base of the tongue. Through a midline lip-splitting incision, a median mandibulotomy is carried out and the tongue is bisected anteriorly in its relatively avascular midline to access the region of the base. After resection of the tumor, the surgical defect is closed primarily and the bisected halves of the anterior tongue are sutured back in layers, usually resulting in excellent postop
erative function. The operation is, however, not advisable if excision of the tumor is likely to result in a substantial soft-tissue defect with a tongue remnant of doubtful viability.
The mandibulotomy approach with paralin-gual extension, the so-called mandibular swing provides the best exposure for resection of most tumors of the oropharynx.16 The site of the mandibular osteotomy directly influences the exposure obtained at surgery and the functional results of the procedure. Table 6-3 describes the salient features of the 3 types of mandibulotomy that have been in common use. We prefer to use the paramedian mandibu-lotomy when extensive access is required to the oropharynx. This operation causes minimal disrup tion of the anatomy of the region and results in fewer functional deficits postoperatively as compared to the other two types of osteotomy.
For a paramedian mandibulotomy, the lower lip is split in the midline and the incision carried over into the ipsilateral gingivolabial sulcus to just beyond the canine tooth. Bilateral flaps are raised for a short distance, dissecting in the plane above the periosteum and taking care to limit dissection to the point where the mental nerve exits the mental foramen. We prefer to use an angled osteotomy (Figure 6-10) that creates a single notch and provides good stability with very little risk of fracture. An oscillating power saw with the thinnest available blades is essential for accurate bony cuts and to prevent
Figure 6-9. Anterior midline labiomandibuloglossotomy.
Table 6-3. SALIENT FEATURES OF THE 3 TYPES OF MANDIBULAR OSTEOTOMY
Site of osteotomy Exposure Dental extraction Inferior alveolar nerve and vessels Division of genial muscles Mechanical stability
Fixation of osteotomy
Postoperative radiation therapy
Through the body/angle of mandible
May be necessary
Must be transected
Poor due to unequal pull of muscles on the two mandibular segments
May require intermaxillary fixation which interferes with maintenance of postoperative oral hygiene
Osteotomy lies within the lateral portal— increased risk of complications
In the midline Good
One central incisor Can be spared
Miniplates or stainless steel wire
Lies outside the lateral portal—safe
Between lateral incisor and canine Good
Not required Can be spared
Not required-only the mylohyoid needs division Good
Lies outside the lateral portal — safe excessive bone loss. The vertical limb of the osteotomy is carried down to a level just beyond the dental apices between the lateral incisor and canine teeth, and the cut is then angled medially. This is possible without extracting the teeth or exposing or damaging their roots because of their diverging configuration (see Figure 6-10). After the osteotomy is complete, the mucosa and muscles of the floor of the mouth are incised posteriorly right up to the anterior pillar of the soft palate. The floor-of-mouth incision must be placed more toward the tongue than the alveolus so that there is an adequate mucosal cuff attached to the alveolus. This step is vitally important to accurate watertight closure of the incision. The lingual nerve and the styloglossus muscle cross
the field, and once they are transected the mandible can be swung out laterally to expose the oropharynx (Figure 6-11).
After resection of the tumor and reconstruction of the defect, the mandibulotomy can be fixed using either stainless steel wires or miniplates with comparable stability.17 Pre-localizing the fixation drill holes on the intact mandible, before the osteotomy cuts are actually made, and fixation in more than one plane are probably more important to accurate dental occlusion and stability than the actual mode of fixation itself. If miniplates are preferred, 2 plates are used across the osteotomy, one on the anterior surface and the other is contoured to fit the inferior edge of the mandible (Figure 6-12). Slight discrepancies in dental occlusion tend to correct themselves spontaneously as the fracture site matures and moulds to the stresses of chewing postoperatively. The lip and neck incisions are then closed in layers over suction drains as usual.
The base of the tongue may be difficult to assess for the extent of a tumor due to its normal nodular-ity—careful palpation is vital to ensure adequate margins as excision proceeds. Advanced tumors of the tongue are associated with diffuse infiltration, and surgical margins have been reported positive by some authors in as many as one-quarter of the cases.18 Frozen-section evaluation of the margins and the base of excision can therefore only minimize the chances of incomplete resection. Partial glossec-tomy may be oncologically adequate for limited
tumors of the base of the tongue, and postoperative functional outcome depends upon the orientation of the resection, the volume of tongue resected, the method of repair, as well as the mobility, sensitivity and the shape of the tongue remnant. Substantial defects of the tongue must therefore be adequately and appropriately reconstructed (Figure 6-13).
Access to posterior pharyngeal wall lesions may require transhyoid or lateral pharyngotomy, median labiomandibular glossotomy or paramedian mandibu-lotomy. Early lesions rarely involve the prevertebral fascia and the intervening avascular retropharyngeal space usually provides a good plane of cleavage during surgical dissection. Superficial lesions that involve only part of the pharyngeal circumference can be excised safely while preserving the larynx.19 Reconstruction of the defect requires thin, pliable tissue such as a split-thickness skin graft or a free radial forearm flap. For more advanced tumors, resectability depends on ascertaining that the under-
lying prevertebral fascia is not involved, a question that is most often resolved only at surgical exploration. Locally advanced pharyngeal wall tumors that involve a substantial portion of the circumference usually require a total laryngopharyngectomy with restoration of pharyngeal continuity using free jejunal transfer or other reconstructive options.
As described above, the mandibulotomy approach provides excellent access to all sites within the oropharynx, and there can be no excuse for resecting the uninvolved mandible solely to gain access to the tumor. Tonsillar or lateral pharyngeal wall tumors that abut against the periosteum of the mandible need marginal resection of the ascending ramus of the mandible (Figure 6-14). More advanced tumors are resected by combining soft-tissue resection en bloc with mandibulectomy, the so-called commando operation (Figure 6-15). Appropriate bony recon-
struction of segmental mandibular defects combined with osseointegrated dental implants is necessary for restoration of useful masticatory function.
Early lesions at some sites such as the soft palate and the posterior pharyngeal wall are at low risk for nodal metastases, and the clinically negative neck in these patients may be safely observed. In all other patients, elective treatment of the N0 neck must be considered. In general, if the primary tumor is treated with radiation therapy, the neck is included in the fields, and if surgical treatment is chosen for the primary, a selective neck dissection is carried out. The uninvolved neck in well-lateralized lesions of the tonsil and tongue may be treated unilaterally, but both sides need treatment in lesions approaching or involving the midline. Dissection of levels II, III and IV generally encompasses the majority of nodes at risk in the clinically N0 neck. Grossly suspicious nodes should be subjected to frozen-section analysis and the dissection extended to include the remaining levels as appropriate. Clinically involved nodes require a comprehensive neck dissection including
all 5 nodal levels, and a modified radical neck dissection preserving the spinal accessory nerve is the procedure of choice. Bilaterally involved nodes are treated with simultaneous or staged bilateral neck dissection. Postoperative radiation therapy is given for the usual indications, based on adverse features of either the primary or the neck nodes.
Locally advanced oropharyngeal tumors can cause considerable difficulty during endotracheal intubation, mainly by obstructing visualization of the larynx, but also because invasion of the ptery-goid muscles may result in trismus. Although fiberoptic endoscope-guided endotracheal intubation is an option, it may be safer to perform a preliminary tracheostomy under local anaesthetic. Patients who have had significant surgical resection and reconstruction require a temporary tra-cheostomy to protect the airway in the postoperative period. A cuffed, low-pressure high-volume tracheostomy tube minimizes aspiration in the early postoperative period. Apart from the ability to tolerate plugging of the tube, factors such as the efficacy of deglutition, the extent of aspiration and the performance status of the patient generally determine when postoperative decannulation of the tracheostomy can be safely undertaken.
Deeply invasive tumors only need to breach the hyoepiglottic ligament to gain access to the pre-epiglottic space (Figure 6-16) from where they can spread to involve the framework of the larynx. Complete excision of such lesions requires either partial supraglottic or total laryngectomy in addition to excision of the base of the tongue.
For practical purposes, major soft-tissue defects of the oropharynx can be divided into those that require thin, pliable flaps for resurfacing and those that need bulkier myocutaneous flaps to provide volume. The posterior pharyngeal wall is an example of the former, and is best resurfaced using either a split skin graft or a free radial forearm flap. On the other hand, substantial defects of areas including the base of the tongue and tonsillar region need reconstruction with bulkier myocutaneous flaps such as the pectoralis major or the latissimus dorsi pedicled flaps or a composite free flap. Pedicled myocuta-neous flaps are generally used to reconstruct partial circumference defects of the pharynx while circum ferential defects are best restored using microvascu-lar jejunal transfer or gastric pull-up. Restoration of mandibular continuity after segmental resection using free-tissue transfer with secondary osseointe-grated dental implants has the potential for resulting in excellent cosmesis and function, and this complex issue has been discussed in other chapters.
Ancillary procedures such as cricopharyngeal myotomy, laryngeal suspension and palatal augmentation may help improve functional results after major glossectomy. Patients who have had major oropharyngeal resection and reconstruction, and those scheduled for postoperative radiation therapy generally require prolonged nutritional support, and a percutaneous endoscopic gastrostomy must be considered at the time of the operation.
Treatment of early tumors of the oropharynx using radiation therapy has been reported to be equally effective as surgical excision20 with the advantage of "superior function." Even for tumors of the base of the tongue21 where the functional results have been
assessed, this "advantage" of radiation over surgery is largely assumed due to selection bias of favorable lesions. There is no prospective randomized trial for cancer of the base of the tongue comparing the two modalities with respect to tumor control and functional assessment. In general, superficial and exo-phytic lesions are best treated by radiotherapy, and deeply infiltrating lesions are best treated by surgery followed with postoperative radiotherapy. Surgical treatment of small lesions at most other sites, with the probable exception of the soft palate, produces very little functional deficit, in contrast to radiation therapy that almost invariably causes irreversible xerostomia and loss of taste, with the potential risk of dental decay and radionecrosis.
For more advanced tumors, initial treatment with nonsurgical "organ-sparing" approaches have recently come into vogue and concurrent chemora-diation therapy seems to hold promise.
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