Definition and Overview
Mandibulectomy is a surgical procedure wherein the mandible (jaw), a crucial bone in the face that contributes significantly to mastication or chewing, is removed or resected. There are several kinds of mandibulectomy depending on the thickness and extent of resection required. Hemimandibulectomy is the type in which half of the mandible is removed.
Who Should Undergo and Expected Results
Hemimandibulectomy is a complex operation, performed for diseases of the lower jaw (mandible), which include:
Tumours - The procedure is usually performed on malignant growths involving either the alveolar ridge and the mandible, or adjacent structures, including the floor of the mouth. It is also indicated for benign masses of the jaw, especially those that are large and have already destroyed the integrity of the jawbone. Tumours of the lower jaw typically present with a palpable mass and jaw pain.
Infections – The procedure can also be recommended for patients suffering from infections of the mandible, such as osteomyelitis.
Mandibular necrosis associated with radiotherapy of the head or neck - In recent years, there has been an increasing incidence of mandibular necrosis due to bisphosphonate use, which may also require hemimandibulectomy.
Traumatic injuries to the jaw resulting in tissue death
As patients are not allowed to eat by mouth immediately after, the procedure is typically followed by the insertion of a tube from the nose into the stomach to allow feeding during the recovery period. Patients are also scheduled for follow-ups, which typically involves physical examinations and imaging studies, such as a CT scan, to ensure the success of the procedure.
How is the Procedure Performed?
A hemimandibulectomy is a major operation performed under general anaesthesia. It is typically approached transcervically, with combined incisions in the face and neck. In some cases, lip-splitting is necessary to gain adequate exposure and easy access to the mass.
The most important principle in head and neck cancer surgery is the complete removal of the tumour with appropriate margins. By convention, clear margins correspond to approximately 5 mm to 1 cm of healthy tissue on all sides. For cases of malignant lesions, the removal of the mass begins by cutting through soft tissue surrounding the tumour. The hemimandible on the affected side is then completely exposed and the involved teeth are removed, making sure that the root fragments are extracted completely. The bone is then cut using an oscillating or sagittal saw. The neurovascular bundle of the bone is divided, and the cut ends are either ligated or cauterised.
As the procedure involves the resection of a significant segment of the mandible, the mandible becomes discontinuous, requiring a reconstructive procedure to maintain the function of the jaw and to cover the defect. Reconstruction may involve the transfer of bone and soft tissue from another part of the body, such as the leg (free flap) to provide adequate structural support to the mandible. The use of a metallic plate with screws for reconstruction is also an option. In some cases, external devices for fixation may have to be put in place. Reconstruction is usually performed together with the resection, but can be delayed in some cases.
In some cases, especially in advanced cancers, hemimandibulectomy may have to be performed with other procedures, such as neck dissection to ensure the complete removal of the tumour with acceptable margins.
Possible Risks and Complications
The goals of hemimandibulectomy are the complete removal of the tumour with clear margins and preservation of a certain degree of mandibular function while ensuring a cosmetically acceptable outcome. However, complications can occur, resulting in less than optimal results.
Possible complications of this procedure include:
- Tumour recurrence - This usually occurs when inadequate resection is performed. For this reason, the specimen is sent for biopsy to check the margins. If malignant cells are seen on the margins or the margins are inadequate, additional surgery is typically carried out.
- Lack of mandibular continuity and inadequate bony support of the lower jaw –Usually due to failed reconstruction, these can produce problems in certain vital functions, such as chewing, swallowing, and sound production. One such complication is malocclusion or the improper position of the jaw such that the upper and lower teeth do not appose well. There is a significant risk for malocclusion in this procedure because a large amount of jawbone is removed.
- Salivary fistula - The development of a salivary fistula can occur especially in patients who have undergone chemotherapy or radiation treatment. In these cases, the saliva leaks into the neck. This requires prolonged placement of a drain or surgical closure of the fistula.
Aside from these, other possible complications of the procedure include bleeding, the formation of seroma (fluid accumulation), infection, and deep venous thrombosis, among others.
- Mandibular resection Dr. Daniel D. Lydiatt DDS, MD* Version of Record online: 18 JUL 2006 DOI: 10.1002/hed.2880170313