Mandibular Osteotomy Approaches

Introduction

The mandibulotomy approach was first described by Roux in 1836. Dubner and Spiro, in 1959, developed the technique with paralingual extension, which is the origin of the modern mandibulotomy. Since then, several modifications to the technique have been described. However, the basic principle of the mandibulotomy still remains, which is to provide exposure and a surgical corridor to the oral cavity and oropharynx. The approach may also be used to access the parapharyngeal space and skull base. The modifications are usually intended to minimize postoperative complications. The two principal types of anterior mandibulotomy are the median and the paramedian.

The median mandibulotomy is performed between the central incisors and may require the extraction of a tooth, owing to the narrow space, with the osteotomy placed in the middle of the tooth socket. This preserves the bone of the adjacent sockets, maintaining the stability of the adjacent teeth. The paramedian mandibulotomy is performed between the lateral incisor and canine and usually does not require tooth extraction.

Key Operative Learning Points

1.
The osteotomy is performed anterior to the mental foramen to maximize blood flow to the bone and facilitate postoperative healing.
2.
Accurate reapproximation of the lip is the key to superior cosmesis. The lip should be closed in three layers: the mucosa, the orbicularis oris muscle, and the skin.
3.
Bone realignment and fixation are enhanced by preplating (placing the plate and drill holes) before proceeding to the mandibulotomy. Use of a stair-step osteotomy facilitates fixation.
4.
Postoperative application of a bulky supportive dressing tends to reduce facial edema and support immobilization, which enhances rapid healing and good cosmesis.
5.
A tracheostomy is necessary to provide an airway during the early postoperative phase. The cannula can be removed as soon as edema resolves and oropharyngeal function has resumed.

Preoperative Period

History

1.
History of present illness
- a.
  Questions about the site of the tumor: tongue, tonsil, gingiva, soft palate
- b.
  Tumor size and growth: how long ago was the lesion noticed?
- c.
  Assessment of function: dysphagia, trismus, dyspnea, dysphonia, aspiration, and weight loss
- d.
  Has a mass in the neck been noted? When? The presence of metastasis of the neck is a major prognostic factor and also important for surgical planning. Often a mandibulotomy is performed in association with neck dissection.
2.
Past medical history
- a.
  History of cancer
- Important to ask about cancer affecting other anatomic sites. Carcinomas of the oral cavity and oropharynx share similar risk factors with carcinomas of lung and esophagus.
- b.
  Dental disease
- Poor dentition increases the risk of wound infection and consequent malunion or nonunion of the mandible. Teeth in poor condition may require extraction prior to or at the time of the osteotomy. Consultation with an oral/maxillofacial surgeon is mandatory. Poor dentition and periodontal disease are important considerations for radiation therapy, as these are major risk factors for osteoradionecrosis (ORN) of the mandible; they should be treated prior to mandibulotomy.
- c.
  Craniofacial anomalies
- d.
  Prior radiation therapy to the head and neck area
- e.
  Diabetes mellitus
- It is well known that diabetes is a risk factor for poor and delayed healing as well as wound infection.
3.
Past surgical history
- a.
  History of craniofacial trauma or orthognathic surgery
- The presence of plates and screws in the mandible can change the osteotomy plan.
- b.
  Facial lacerations, especially in the inferior lip, vermilion, and chin
- Any preoperative scars should be well documented in order to avoid confusion with cosmetic sequelae resulting from the surgical approach
- c.
  History of tracheostomy or tracheal surgery
- The surgeon should anticipate difficulties during the tracheostomy owing to scar from previous surgery. Was it an emergent tracheostomy or a planned one? Was it a percutaneous endoscopic or classical tracheostomy?
- d.
  History of any head and neck surgery
4.
Social history
- a.
  Tobacco and alcohol use
- Both are well-established risk factors for oral cavity and oropharyngeal squamous cell carcinoma.

Physical Examination

1.
Careful inspection of the head and neck is important to search for scars that might suggest previous facial trauma or surgery. Scar in the anterior neck may represent a prior tracheostomy. The skin should also be assessed, especially in patients with a history of radiation therapy.
2.
Information about the size of the tumor, location, infiltration, and cranial nerve involvement can be assessed with a thorough physical examination, including inspection and palpation.
3.
In case of severe trismus, intraoral palpation is compromised and further assessment of the lesion can be done with complementary examinations.
4.
Flexible transnasal laryngoscopy is a good option to evaluate extension of the tumor to the hypopharynx and larynx, especially in patients with severe trismus.
5.
Palpation of the neck is important for the diagnosis of metastasis to the cervicallymph nodes.
6.
Careful inspection of the teeth and gingiva is important. Swelling and hyperemia of the gingiva in the presence of tenderness to palpation are suggestive of periodontal disease. A dental consultation should be ordered accordingly.

Imaging

1.
Panoramic radiography: Important in order to study the site of the osteotomy. Information regarding the angulation and distance between the tooth roots can be obtained. If a stair-step osteotomy is planned, the distance between the apices of the teeth and the border of the mandible at the osteotomy site should be measured.
2.
Computed tomography (CT): Important in order to detect bone involvement. Invasion of the mandibular cortex is often best studied with CT scans. The presence of bone involvement is a contraindication to the mandibulotomy approach.
3.
Magnetic resonance imaging (MRI): Possible spread through the medullary space may be better identified with MRI.

Unfortunately, imaging techniques may miss subtle involvement of bone by tumor. If there is a rim of normal tissue between the tumor and bone, the mandible may be spared. There is no substitute for good clinical judgment.

Indications

1.
Tumors located in the posterior aspect of the oral cavity and oropharynx may be best suited for a mandible-sparing procedure if the periosteum of the mandible is not infiltrated by the cancer.
2.
The mandibulotomy approach should be considered if the transoral approach fails to provide good enough exposure to ensure clear margins for lesions involving the soft palate, tonsil, base of the tongue, and/or retromolar trigone.
3.
With the advent of transoral robotic surgery (TORS), the regions that can be resected transorally with clear margins have increased. Some cancers that previously would have required an osteotomy of the mandible for approach and resection are currently being successfully treated with TORS. (See Chapter 99 , Transoral Robotic Surgery.)
4.
Larger and more infiltrative cancers still require a mandibulotomy approach to provide enough exposure for complete resection. Additionally, reconstruction is greatly facilitated and healing enhanced if the repair is performed with a comfortable surgical exposure.
5.
Intact dentition and severe trismus interfere with the transoral approach.
6.
In resecting cancers involving the base of the tongue, tonsillar fossa, soft palate, and/or retromolar trigone, the choice between using the mandibulotomy approach and TORS usually depends on the surgeon’s preference and/or experience. Both techniques have been effective in the treatment of oropharyngeal cancer.
7.
If the cancer is fixed to the periosteum but does not invade the cortex, a marginal mandibulectomy is preferred. (See Chapter 181 ).
8.
A combination of marginal mandibulectomy and anterior mandibulotomy is to be avoided because it is frequently associated with a pathologic fracture postoperatively.
9.
Exposure in patients requiring a marginal mandibulectomy may be improved by using a midline lip- and chin-splitting incision and elevation of the facial flap. This technique is appropriate in patients in whom the transoral approach would be inadequate for a marginal mandibulectomy and excision of the cancer.
10.
If the mandible is grossly invaded, a segmental mandibulectomy is essential. The area of bone to be removed is determined preoperatively, and osteotomies are created during surgery to facilitate exposure and complete resection of the cancer.

Contraindications

1.
If the cancer has invaded the mandible, mandibulotomy is not appropriate. Such patients require a segmental mandibulectomy to achieve clear margins.
2.
When the periosteum is involved but the cortex is intact, a marginal or rim mandibulectomy should be considered.
3.
Segmental mandibulectomy is recommended if the cortex of the mandible or marrow space is involved by cancer. The space obtained after segmental mandibulectomy is used to gain access to the oral cavity and/or oropharynx for complete resection of the cancer. In this case the reconstruction is performed with free flaps; fibular free flaps are commonly used.

Preoperative Preparation

1.
After the preoperative evaluation, the surgeon should be able to decide on the best surgical approach to the cancer: transoral, mandibulotomy, or mandibulectomy.
2.
In some cases the preoperative plan can change, but that would be an exception. In challenging situations, any possibility of modification of the surgical plan should be anticipated by the team and explained to the patient.
3.
Physical examination is critical to detect invasiveness of the cancer; when this is associated with radiologic findings, accuracy is increased.
4.
The best clinical examination is performed with the patient under general anesthesia.
5.
In the imaging studies, it is sometimes difficult to distinguish a subperiosteal reaction from invasion. These studies are also important to evaluate the cervical lymphatics. MRI enhances the soft tissue interfaces, whereas CT better delineates the interface between bone and soft tissue. Neither imaging technique, however, can detect subtle degrees of bone involvement.
6.
Where tumor is in close proximity to the mandible, intraoperative frozen section pathology is important for evaluation of the periosteum.

Operative Period

Anesthesia

General anesthesia is established and—if there is no contraindication, such as severe trismus—orotracheal intubation is performed.
Where orotracheal intubation is impossible, fiberoptic nasal intubation is performed. It is imperative for the surgeon to be in the room, helping the anesthesiologist, during the intubation of patients with oral cavity/oropharynx tumors.
After the airway has been secured, a tracheostomy should be carried out and the endotracheal tube removed from the oral cavity, thereby improving the exposure.
Primary awake tracheostomy is indicated in cases of severe compromise of the airway.

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