Christopher H. Rassekh
Marginal mandibulectomy can be defined as any removal of a portion of the mandible that does not result in a segmental defect. Marginal or nonsegmental mandibulectomy can be divided into three basic types (Table 15.1): (1) inner table mandibulectomy (intraoral), (2) alveolar ridge or superior rim mandibulectomy (intraoral), and (3) outer table mandibulectomy (extraoral). Outer table mandibulectomy is occasionally performed, mainly for tumors that adhere to the periosteum of the outer cortex. For example, skin cancers, cancers of the lower lip, inferior buccal sulcus cancers, or lymph nodes in the region of the facial artery may be adherent to the lateral mandibular periosteum. These are best managed by resection of the outer table of the mandible and preservation of the inner table. The technical principles are the same, so this chapter focuses on the intraoral techniques.
Inner table mandibulectomy can be performed on the anterior or lateral mandibular region for cancer of the floor of mouth, retromolar trigone, or gingiva. When cancers of the gingiva are isolated to the alveolar ridge and/or buccal mucosa, marginal mandibulectomy may spare some of the inner table. Often, inner table mandibulectomy and alveolar ridge mandibulectomy are combined, preserving an adequate strut of outer table to prevent fracture. In general, preserving 11 mm of vertical height is the minimal strut to minimize the risk of fracture. This is not a hard and fast rule because the length of the defect likely contributes to any instability as well. In some patients, the stability of the remaining bone may be reinforced with a titanium plate.
When evaluating a patient for possible marginal mandibulectomy, it is important to determine other aspects of the patient’s cancer and comorbidity and to be informed of any prior therapy, especially any prior radiotherapy or surgery, including dental procedures. In addition, any history of trauma to the mandible or surrounding region should be sought. It is also important to assess the patient’s specific needs with regard to dental rehabilitation and mastication.
Preoperative assessment of the extent of tumor involvement is critical. Physical examination remains the most reliable predictor of the extent of mandibular involvement, and various radiographic techniques can be used as an adjunct and may upstage some patients. Often irregular bone can be palpated in the crater of an ulcerated cancer. Palpation of the tumor may require examination under anesthesia due to pain. The dimension and location of the tumor should be recorded for staging purposes.
TABLE 15.1 Types of Marginal Mandibulectomy (Nonsegmental Mandibulectomy)
Indications for marginal mandibulectomy are discussed in the Introduction and are summarized in Table 15.2.
Marginal mandibulectomy should not be performed in patients who have through and through destructive lesions of the mandible or in those patients who have gross invasion of the marrow of the mandible by tumor and is generally reserved for patients who are suspected by clinical or radiographic examination of having periosteal invasion or limited invasion of cortical or alveolar ridge bone. Patients who have lesions in the lateral mandible and who have had prior radiotherapy are less suitable candidates for nonsegmental resections (Table 15.3).
Patients should be counseled that if the tumor is adherent to the bone, but if they are then found at surgery to have evidence of invasion, a more extensive (segmental) mandibular resection may be required. Reconstruction for segmental defects is more complex, and this requires careful counseling. In some cases, such a procedure may be staged.
CT, MRI, plane films, bone scan, and dentascan may all play a role depending on the situation. Perhaps the most useful imaging study is the bone window of a fine-cut CT scan to assess integrity of the cortex in multiplanar fashion. T1-weighted and T2-weighted and short T1-inverted recovery MRI are often useful to rule out marrow invasion. One should be cautious about reactive bone changes that may be seen on imaging and rely on clinical examination when there is a discrepancy until proven otherwise to avoid an unnecessary segmental resection.
Marginal mandibulectomy is a highly effective procedure in the proper setting. Nonsurgical management of such lesions is suboptimal in terms of both local control and morbidity because radiotherapy is a less effective oncologic treatment for these lesions. Even when it controls the cancer, the entire mandible is compromised by radiotherapy and may eventually be destroyed by osteoradionecrosis.