Mandibulectomy Technique

Mandibulectomy can be performed transcervically, requiring face and neck incisions that allow external exposure to the mandible, or it may be performed transorally, in which all incisions are placed intraorally. In general, the disease process drives the approach taken.

For a benign process that involves the mandible and for small-to-moderate malignant processes, it is possible to perform the resection completely transorally in some patients.

For transoral approaches, particularly in benign disease, the mucosal incisions are made very close to the teeth that are to be resected or very close to the alveolar ridge in the patients who are edentulous. Incisions can be made farther than the limits of the bone resection to allow improved exposure and to place preresection and postresection mandibular plating devices. In patients with a benign process, once the mucosal incisions are made, both medial and lateral to the mandible and across the alveolar ridge at the point of resection, a periosteal dissector can be used to elevate the soft tissues off of the mandible. Once the mandible is completely exposed transorally, the appropriate plate can be placed preresection.

In patients with extensive malignant disease that will require wide resection, a transcervical approach with lip splitting or visor flap incisions are most appropriate. Key to the ability to render the patient disease free of oral cavity carcinoma is complete extirpation of the tumor with histologically clear margins. The authors expect a minimum of 5 mm on permanent fixed section to truly call a margin clear. Bony resection margins must also be histologically clear, and at least a 1-cm gross margin should be taken at the time of tumor resection.

As noted above, a reconstruction plate should be placed, if at all possible, prior to any full-thickness resection of the mandible. In patients with an intact lateral mandibular cortex, the lateral surface of the mandible may be used as the template on which to bend a conforming mandibular reconstruction plate.

Typically, the soft metal template that comes with the plating system is used to obtain the general shape and form of the lateral mandibular cortex; the actual fixation plate is then bent based on the dimensions of the soft metal template. Once the gross changes are made in the mandibular plate, it is fine-tuned by applying the plate directly against the lateral border of the mandible. Knowledge of the anticipated osteotomy sites is helpful, since it is generally desirable to have 3 screws present on either side of the mandibulectomy (see image below).

A postoperative picture of the reconstruction plate with 3 screws on either side of the mandibulectomy.

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This requires that 3 solid hole purchases are placed into the native mandible. In patients in whom a preoperative computer-generated prebent plate has been made, it will be placed after the mandibulectomy is performed.

Prebent plates are now available from some vendors that are said to conform to the vast majority of human mandibles and may require only minimal contouring (see image below). ^[7]

Prebent reconstruction plate fixed onto computer-generated mandible model.

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In patients with a tumor that has “blown out” the lateral cortex of the mandible, the authors often use an external fixation device. By fixing the mandible on either side of the proposed resection site to the external fixation device, proper occlusion can be maintained by maintaining the proper alignments across the defect of one mandibular remnant to the other. ^[8] The external fixation set can be used to allow maintenance of the proper mandibular segment relationship, even when a computer-generated mandibular reconstruction plate is available, as this allows, during all portions of the resection, for mandibular segments to be in proper alignment with one another. In addition, an external fixator device allows the mandibular condyles to be in proper position in the glenoid fossa (temporomandibular joint) during the reconstruction (see image below).

External fixator in place after mandibulectomy. This will allow proper alignment of the remaining segments of the mandible and proper alignment of the condyle in the glenoid fossa.

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Soft-tissue exposure is important for allowing excellent visualization of resection of the benign tumor or a malignant process. Gross 1-cm margins are desirable both on soft tissue and bone. Therefore, the resection is performed with a 1-cm minimum margin of what is believed to be healthy mandible on either side of the tumor. The cuts are either made with a sagittal or reciprocating saw, depending on the surgeon’s preference. Once the inferior alveolar neurovascular pedicle is divided, this will need to be addressed with cautery.

It is common practice to shape and place a reconstructive plate onto the native mandible before the mandible is resected. In doing this, the surgeon must drill holes in the native mandible and place screws to secure the plate to the underlying bone. Just prior to resection, any plates and screws that had been placed preresection are removed. The advantage of drilling the holes preresection is that, when the plates are reapplied postresection, the holes that have been previously drilled and the mandibular segments are maintained at proper alignment with one another, thereby sparing the occlusion.

In patients undergoing less than full-thickness segmental mandibulectomy, the inner table alone can be resected. In general, teeth in patients who are undergoing inner-table mandibulectomy may need to be extracted, and the sagittal saw can then be used to take the inner cortex of the mandible. The fresh dental-extraction socket generally makes an excellent parasagittal plane on which to place the saw and to resect the medial half of the mandible, leaving the lateral half of the marrow cavity and the lateral cortex intact.

Reconstruction of the mandible is beyond the scope of this discussion.

In some cases, nothing more than a reconstruction bar is used for rigid reconstruction of the mandible. In these cases, the mucosal edges of the resection can be closed onto themselves. Generally, it is best to close the lateral buccal mucosal margin to the medial lingual mucosal margin using absorbable 3-0 Vicryl sutures.

Postoperatively, patients are kept NPO for a variable period to allow the intraoral suture line to close before stressing it with chewing and movement, as well as bolus in the oral cavity. Among patients who have undergone a mandible reconstruction using a free-tissue transfer, 7-10 days should generally elapse before an oral intake diet is begun. The same will hold true for patients closed primarily.

One of the dangers of closing the mucosa primarily over a reconstruction bar is that a dead space is created that is nonvascularized, which will lead to mucosal breakdown and plate extrusion.