The need for reconstruction of mandibular defects is either due to trauma or tumor resection.
The vast majority of oral cavity tumors are squamous cell carcinoma, and typically arise from the floor of mouth or adjacent alveolar mucosa. These tumors are therefore adjacent to the mandible and significant growth frequently leads to invasion of the bone.
A composite resection (segmental mandibulectomy) is the treatment of choice for oral malignant tumors that invade the mandibular cortex and marrow space. It provides an oncologically sound margin for these tumors; however, it disrupts the continuity of the mandible.
General goal of reconstruction
Reconstruction of the mandible allows for the restoration of form and function. It must address all the tissue losses in order to provide for the best function.
The general goal of reconstruction is the:
Restoration/maintenance of airway
Restoration of chewing (mastication) and swallowing (deglutition)
Restoration of osseous union
Restoration of facial contour
Restoration of oral dentition, in dentate patients
Consistently obtain a healed wound
However, when bony reconstruction is not desired or possible, the restoration of the intraoral soft tissue defect with a vascularized soft tissue graft alone is a reasonable alternative.
This creates the so-called "swinging defect". The mandible shifts to the affected side resulting in a cosmetic deformity, but often allows for acceptable speech and adequate swallowing.
The location and size of the tumor will dictate the surgical approach necessary for the performance of the ablative procedure.
The two following approaches are frequently used for the mandible:
Incisions are marked out 1.5 cm around all visible and palpable tumor.
An extension of the incision is then carried posteriorly towards the mastoid and anteriorly to the submental region. Additional extensions can be made according to surgeon's preference to allow for simultaneous neck dissection.
A lip split incision can be added if necessary to improve access and visualization of the mandibular condyle.
When the neck dissection is performed, care must be taken to dissect and preserve potential recipient vessels.
It should be noted that on most occasions one or more branches of the facial nerve will need to be sacrificed due to tumor involvement.
Skin incision around tumor
Dissection is carried through the skin incisions marked around the tumor and continued through the subcutaneous tissues until the mandibular bone is encountered.
Externally, the masseter muscle will be divided on the lateral aspect of the mandible if it is not included in the resection.
The periosteum is incised keeping at least 1 cm margins around the involved mandibular bone. The periosteum and soft tissues on the remaining native mandible are elevated proximal to the proposed anterior mandibular resection margin to allow for subsequent closure. The proposed line for the mandibular osteotomy is outlined.
Extraction of tooth
In a dentate patient the tooth in the line of the mandibulectomy is extracted.
The bone cut is now carried anterior to the tumor using a saw. Care is taken to resect a 1 cm margin of normal bone anterior to the tumor.
The tumor is visualized and 1.5 cm soft tissue margins are marked (eg. with an electro cautery) around all visible or palpable tumor in the oral cavity.
Removal of the bone segment and tumor
The bone is retracted laterally, thus exposing the previously marked resection margin.
Medially, soft tissue cuts are made through the floor of mouth, the mylohyoid muscle, and deep tongue muscles if necessary.
Medially, the attachments of the medial pterygoid are released from the ascending ramus and the temporalis muscle is detached from the coronoid process.
Laterally, the extension of the soft tissue resection depends on tumor infiltration and could include the masseter muscle, parotid gland, and facial nerve branches.
The lateral pterygoid muscle is divided and the capsule of the temporomandibular joint is entered.
The condyle is retracted inferiorly and the ligaments divided thus freeing the mandible.
The specimen is submitted en bloc for permanent pathological examination.
Surgical soft tissue margins are now checked with frozen sections to ensure the adequacy of the tumor resection.
An adequate length of the flap must be ensured to allow a skin paddle of adequate size to reach to the oral cavity defect without tension.
The cutaneous portion of the flap will be used for both the intraoral and the external closures with an intervening de epithelized segment.
If sufficient skin is not available from the flap, the muscle can be closed to the external skin defect.
The flap pedicle is passed from the chest wall to the defect trough a subcutaneous tunnel in the neck (usually in the case of simultaneous neck dissection) or alternatively, the pedicle stays outside the neck adequately protected.
Placement and closure of skin/soft tissue component
The cutaneous portion of the flap is closed to the oral mucosa defect with interrupted vertical mattress sutures (eg. 3-0 Vicryl). A water tight closure is essential to avoid a salivary leak into the neck with subsequent infection in the surgical site and an orocutaneous fistula.
An intervening segment of skin must then be de-epithelized and this will lie in the deep tissues of the cheek.
The remaining skin is used to close the external cutaneous defect.
If sufficient skin is not available from the flap, the muscle can be closed to the external skin defect. The raw surface of the muscle may be grafted with split thickness skin or dressed and allowed to granulate.
5. Aftercare following mandibular reconstruction
The use of the following perioperative medication is controversial. There is little evidence to make strong recommendations for postoperative medications.
Analgesia as necessary
Antibiotics (many surgeons use perioperative antibiotics). There is no clear advantage of any one antibiotic but evidence supports their use for 24h. The spectrum should be according to the oral bacterial flora, but the physician should be aware of changes that may occur after the use of radiation therapy.
Steroids may help with postoperative edema.
Regular perioral and oral wound care has to include disinfectant mouth rinse, lip care, etc.
Antibiotic ointment is used on the wounds for 72 hours
If a free flap is utilized for the reconstruction, 80-100 mg of aspirin/day is recommended.
Remove any sutures from skin after approximately 7 days if nonresorbable sutures have been used. If the patient has had previous radiation, the sutures should be left in for 10 – 14 days. Wound should be cleaned at least twice daily with hydrogen peroxide or mild soap and water. Moisturizing lotion should be used on the skin wounds to minimize excessive scarring after sutures are removed. Avoid sun exposure and tanning to skin incisions for several months.
Diet depends on the reconstructive method. In general patients with superficial wounds can begin an oral diet within 48h postoperatively. Patients who have undergone a more significant surgery eg. flap reconstruction are kept NPO for 5-10 days and nutrition is administered via nasogastric tube. Oral feedings are begun using thickened liquids only after swallowing is assessed by the surgeon or the speech pathologist, and the risk of aspiration is minimal. Diet can be advanced as tolerated by the patient.
Typically the patients are seen in clinical follow-up one week after discharge, and then on a weekly basis until such time the clinician determines that less frequent follow ups are needed.
Patients with intraoral incisions and/or wounds must be instructed in appropriate oral hygiene procedures. A soft toothbrush (dipped in warm water to make it softer) or water flosser should be used to clean the surfaces of the teeth. Chlorhexidine oral rinses should be prescribed and used at least 3 times a day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris.
Reconstruction with free flap
When a free flap is utilized, it should be regularly monitored to ensure vascular integrity. Physical examination, assessing the flap color, turgidity, and capillary refill should be routine for at least the first 48 hours postoperatively. Hand-held Doppler probes can be used to assess blood flow. In case of doubt of the vitality of the flap, pin-prick assessment with a 25 gauge needle to look for bright red bleeding.. In cases of buried flaps, an implantable Doppler placed just distal to the venous anastomosis can be utilized.
Closed suction drains are routinely used at the donor site. The drain is removed when output is <30cc per 8 hour period, for three consecutive periods. Patients are typically discharged from the hospital 5-10 days after surgery, depending on their postoperative course and comorbidites. Close outpatient follow-up after discharge is recommended for evaluation of surgical sites.
Radial forearm free flap The radial forearm free flap donor site should be closed with a skin graft and a bolster placed over the area. The arm is then cast or placed in a volar splint for 7 days prior to removal to ensure graft take.
Fibula free flap After a fibula free flap, the donor lower leg should be cast with the ankle slightly dorsiflexed for 5 days. The patient can touch-down their body weight as tolerated. After the cast is removed they can ambulate and work with physical therapy to optimize leg function. A splint should be placed to keep the foot flexed when in bed. The routine use of a compression stocking for one month postoperatively will reduce the amount of lower leg dependent edema and aid in improved wound healing.
Scapula free flap In the initial postoperative recovery, the ipsilateral arm should be positioned anteriorly and medially, usually supported on the patient’s abdomen by a pillow. Once the patient is ambulating, the arm is supported by a shoulder sling which supports the elbow and prevents inferior drift of the arm. Inpatient physical therapy is initiated once the patient is mobile. A post-operative physical therapy regimen is established with the patient to be maintained after hospital discharge. The sling is used for 2-3 weeks and physical therapy maintained until postoperative function is optimized, usually 4-6 weeks.
Iliac crest The iiliac crest donor site requires that the patient not strain or lift heavy objects for at least 4 weeks to avoid hernia formation. Patients are typically limited to a bed or chair for 48h postoperatively and then physical therapy is begun with the patient initially ambulating with the aid of a walker or cane and progressing as tolerated.
Latissimus dorsi No specific rehabilitation is necessary following the use of this flap.