CC
A 56-year-old White male is referred to your office with “worsening pain in the right side of my jaw, difficulty opening my mouth, and numbness of my lower lip and chin.”
HPI
The patient was diagnosed with a human papillomavirus p16–positive squamous cell carcinoma of the base of tongue 6 years prior. This was pathologically staged T3N3M0 (American Joint Committee on Cancer 8th edition), for which he underwent chemoradiotherapy treatment with curative intent. This consisted of 70 Gy to the base of tongue and bilateral neck in 35 fractions with concurrent cisplatin chemotherapy.
The patient then underwent extraction of his #17 and #18 teeth 2 years ago because of chronic pericoronitis arising from the distal aspect of tooth #17. His recovery from these extractions was prolonged, and 6 months afterward, he developed progressive paraesthesia in the third division of his left trigeminal nerve as well as ongoing pain and trismus. An orthopantomogram (OPG) at that time demonstrated an osteolytic process in the left mandible with a subsequent computed tomography (CT) scan demonstrating a nondisplaced pathological fracture of the left angle of the mandible. A diagnosis of stage III osteoradionecrosis (ORN) (Notani classification) of the mandible was made.
A discussion was held with the patient at this time regarding surgical resection and reconstruction. It was the patient’s preference, in discussion with the treating team, to pursue a trial of conservative therapy with tocopherol and pentoxifylline with soft diet. His symptoms at this time were well managed with preserved ability to chew, mild mouth opening restriction, and no overlying skin changes or orocutaneous fistula formation. A follow-up OPG showed bony healing of the nondisplaced fracture of the left angle of the mandible.
In the following year, the patient developed ORN of his right mandible, with radiographic changes extending from the right body to the ipsilateral condyle; his left-sided disease demonstrated marked improvement. Oral antibiotics were commenced in addition to the tocopherol and pentoxifylline. However, throughout the review period of a further 12 months, there has been significant progression of the trismus (12 mm interincisally) as well as pain and paraesthesia in his right third division of the trigeminal nerve. He underwent a debridement of his right mandible with extraction of the #32 and #31 teeth without improvement 3 months ago and has now been referred to you for definitive management ( Fig. 78.1 ).
PMHX/PDHX/medications/allergies/SH/FH
The patient is otherwise well with no medical comorbidities. He does have an allergy to penicillin.
Examination
General. The patient is a well-nourished male in no acute distress. (Morbid obesity and severe peripheral vascular disease would be contraindications to microvascular surgery.)
Vital signs. Vital signs are stable and within normal limits. The patient is afebrile.
Maxillofacial. There is no change in the skin overlying the maxillofacial skeleton, but the patient does have tenderness on palpation along the right lower border of the mandible. There is altered sensation of bilateral third divisions (V3) of the trigeminal nerve at the mental nerve distribution. There is no palpable cervical lymphadenopathy.
Intraoral. There is exposed bone along the crest of the mandible at the #32 and #31 teeth sites. The remaining teeth do not have any apparent caries and are nonmobile.
Extremity. The patient has 2+ peripheral pulses without claudication or evidence of peripheral vascular insufficiency.
The lower extremities should be examined to evaluate for absent or diminished pulses in the anterior or posterior tibial arteries because this may suggest atherosclerosis or vascular insufficiency. Absent or diminished anterior or posterior tibial pulses mandate a preoperative angiogram or magnetic resonance angiogram to define the vascular anatomy.
Imaging
The panoramic radiograph and CT scan can be used to help determine the extent of the mandibular resection to aid in predicting the size of the postresection mandibular defect and for use in virtual surgical planning (VSP). A CT slice thickness of 1 mm or less is required for VSP.
In the current patient, the OPG showed an extensive lytic lesion of the right mandible involving the body and ramus and approaching the condyle (see Fig. 78.1 ).
Preoperative imaging for the fibula should include CT angiography (CTA) or magnetic resonance angiography (MRA) of the lower extremities to evaluate the vascular anatomy for the possible absence or diminished size of the anterior and posterior tibial arteries and for narrowing or occlusion of the vessels secondary to atherosclerosis. In about 10% to 20% of cases, the anterotibial or posterotibial artery may become attenuated; this is known as peronea magna . In these cases, a communicating branch from the peroneal artery supplies the attenuated vessel’s territory; therefore, sacrifice of the peroneal artery could result in ischemia of the foot.
Preoperative CTA or MRA to evaluate lower extremity vasculature has become routine with their increased availability, the increase in use of VSP, and the decrease in cost and radiation. The authors perform a clinical vascular examination, supplemented with a lower extremity CTA, for patients who are to have a fibula free flap for vessel assessment and VSP. Conventional angiography is reserved for patients with severe vascular disease or if the prior studies were inadequate.
Labs
Routine laboratory tests, such as a complete blood count and electrolytes, coagulation studies, and liver function tests are performed to establish a baseline preoperatively.
Assessment
Stage III ORN of the mandible.
Treatment
The current patient presents a complex case with a previously irradiated oral cavity and necrosis of the bone. The core principle of ORN treatment is to remove nonviable or necrotic bone to allow bony healing (see Chapter 7 ).
The current patient has now failed medical and conservative surgical therapy with progression of his disease both symptomatically and radiographically. In discussion with the patient, it was decided that resection and reconstruction of the mandible was now indicated.
The goals of mandibular reconstruction include the following:
- •
Reestablishment of mandibular continuity and arch form and maintenance of the existing occlusion, with care taken to maintain the restored mandible’s proper relationship to the maxilla to allow dental rehabilitation
- •
Provision of soft tissue closure and replacement of resected oral cavity soft tissue
- •
Dental rehabilitation
- •
Restoration of adequate function (speech, mastication, oral continence) and cosmesis, enabling the patient to enjoy a reasonable quality of life
Several treatment options are available, each associated with specific complications and limitations that reflect the difficulty of managing total mandibular reconstruction. These treatment options include:
- •
A vascularized soft tissue flap with or without mandibular reconstruction plate
- •
A nonvascularized bone graft (e.g., iliac crest, rib)
- •
A vascularized bone flap (e.g., fibula, ilium, radial forearm, scapula)
The use of a vascularized soft tissue flap to reconstruct a segmental mandibular defect is typically reserved for patients who are not suitable for bony reconstruction because of reduced life expectancy or comorbidities. This is because of the inability of a soft tissue only flap to sufficiently address the goals of mandibular reconstruction stated above. Patients who undergo vascularized soft tissue flap reconstruction with a mandibular reconstruction plate are at significant risk of complications, including plate exposure in up to 46% of patients, loss of fixation, plate fracture, and orocutaneous fistula formation.
Nonvascularized bone grafts of up to 6 cm can be used in mandibular reconstruction; however, they require well-vascularized, intact mucosa and nonirradiated wound beds, making them an unsuitable choice. Free vascularized bony grafts provide the optimal treatment option for segmental mandibular reconstruction and in particular the fibula free flap. This is because of several factors, including the length of bone available, the thickness of the bone, the length of the pedicle, vessel caliber, and the possibility of a reliable skin paddle.
The patient was treated with VSP segmental mandibulectomy, right neck dissection for vascular access, tracheostomy, and immediate reconstruction with an osseous fibula free flap with three osseointegrated implants and immediate fixed dental prosthesis.
Virtual surgical planning
A VSP session was undertaken before the surgery to plan the extent of the mandibular resection. The reconstruction and position of the fibular was planned by carrying out a digital wax-up of the patient’s missing dentition (teeth #28, #29, #30, and #31). The ideal position of the implants was determined, and the fibula segments were placed to ensure the implants are well within the bone ( Fig. 78.2 A and B). This usually results in the fibula’s being placed slightly more superior from the lower border ( Fig. 78.2 C and D). A minimum of 6 cm of distal fibula is maintained to maintain ankle stability ( Fig. 78.2 E).
Patient-specific three-dimensional printed anatomic models (biomodels) were created of the pre- and postoperative mandible and fibula. Furthermore, cutting guides for the mandible and fibula as well as a patient specific reconstruction plate were created. The dental prosthesis was printed with a toothborne guide to aid in setting the occlusal height ( Fig. 78.3 ).
Surgical technique
The patient underwent a general anaesthetic and tracheostomy to secure his airway. A right submandibular incision was made deep to the platysma, and a subplatysmal flap was raised. Next, the marginal mandibular branch of the facial nerve was preserved by elevating the deep cervical fascia, exposing the submandibular gland. The submandibular gland was removed to allow dissection of the facial artery and facial vein as recipient vessels for the microvascular anastomosis. The external jugular vein was also identified and isolated as the second recipient vein. Dissection was continued to the lower border of the mandible before a mucoperiosteal flap was raised intraorally from the right posterior mandibular alveolus to the position of the left mandibular canine. In accordance with the VSP, the cutting guide was then fitted to the mandible and secured. The mandibular osteotomy was then performed with a reciprocating saw through the right mandibular first premolar tooth socket, and the right hemimandible was delivered ( Fig. 78.4 A), with ligation of the right inferior alveolar neurovascular bundle and preservation of the right temporomandibular disc.
Stay updated, free dental videos. Join our Telegram channel
VIDEdental - Online dental courses
