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 these arise from the 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 mandibular continuity
Restoration of dentition
Restoration of chewing (mastication) and swallowing (deglutition)
Restoration of facial contour
Consistently obtain a healed wound
Internal fixation hardware
Mandibular fixation is best achieved with the use of a load bearing locking mandibular reconstruction plate.
A wide variety of options are currently available:
2.4 Uni-lock reconstruction plates
Matrix mandible reconstruction plates of different profiles (2.0, 2.5, 2.8), and screw diameters
For illustration purposes we will show the use of a 2.4 reconstruction plate.
The advantage of the locking plate is that it does not require 100 % adaptation to the mandibular contour. Small gaps can be tolerated since the threaded screw head locks to the plate resulting in an internal "ExFix" construct.
Microvascular free tissue
Mandibular reconstruction with microvascular free tissue transfer is generally used for complex defects following tumor resection and trauma with tissue loss. It provides:
Soft tissue and bone for the restoration of composite defects.
A one stage procedure, allowing for timely adjuvant therapy for oncologic purposes, when necessary.
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:
The proposed mandibulectomy margins are marked on the mandible. Care is taken to resect at least 1 cm of normal bone on each side of the tumor.
Defining the soft tissue margins of the composite resection
The tumor is visualized and palpated intraorally and 1.5 cm soft tissue margins are marked (eg. with electro cautery) around the tumor in the oral cavity.
A template is contoured to the external mandible staying just superior to the inferior border of the mandibular body.
At least 3 fixation screws are planned on either side of the mandibulectomy.
To avoid a prognathic situation of the reconstructed chin, and to facilitate the dental implant positioning, the template at the symphyseal area should be contoured above the chin, in the midportion of the mandibular height.
The plate is then bent to match the template. The plate is placed onto the mandible and final adjustments are made to produce a near perfect passive fit.
A minimum of three bicortical fixation screw holes are drilled and locking screws inserted through the most proximal and distal plate holes.
Note: The screws close to the resection border should be at least 5-7 mm away from the osteotomy line.
The screws and plate are then removed, tagged and placed on the back table.
The plate will usually be used as a template for trimming the graft. The margins of the defect are marked on the plate with wires or sutures.
If the trimming of the bone to the plate is done at the donor site, the plate should be re-sterilized.
Pearl: In order to return the proper length screw into its respective hole, the screws can be organized in a screw caddy as shown.
Extraction of teeth
In a dentate patient, the teeth in the line of the osteotomies are extracted.
Bone cuts are now carried on both sides of the tumor using a saw. Care is taken to resect at least 1 cm of normal bone on each side of the tumor.
Removal of the bone segment and tumor
The bone is retracted anteriorly/anterolaterally, thus exposing the resection margin.
Soft tissue cuts are made through the previously marked resection limits in the floor of mouth, the mylohyoid muscle, suprahyoid muscles and deep tongue muscles if necessary.
If the contralateral distal submandibular duct must be divided due to tumor involvement, the residual duct should be reimplanted into surrounding oral mucosa using a sialodochoplasty technique.
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.
The skin segment of the fibula flap is quite reliable and thin and is used to close the mucosal defect of the floor of mouth and adjacent tongue.
Either fibula can be used for a given defect. The choice of side is dependent on the vascular supply to the lower leg (determined by preoperative studies) and the recipient vessels in the neck.
Contouring of the bone graft
The harvested bone graft is now measured against the plate or template, usually on a side table or donor site (eg. Fibula). Minor final adjustments are performed in situ.
It is best to measure a small excess of bone when first trimming, particularly if osteotomies will be necessary to shape the bone, in order to compensate for bone loss during the subsequent steps. Any excess bone can then be trimmed prior to final insertion and fixation.
Excess bone of the flap is measured and stripped of periosteum.
The bone is now trimmed with a saw to fit the defect. Care is taken to avoid injury to the vascular pedicle during this procedure.
Pitfall: If a burr is used to trim the bone, it may catch the periosteum and hence, damage the vascular pedicle
Care must be taken to not injure the vascular pedicle during the closing ostectomies. Therefore, the periosteum should be freed from the bone resected during the closing ostectomy and retracted carefully during the bone cuts. Excessive stripping of the periosteum around the closing ostectomy will put the vascular supply of the segment at risk.
The bone should be contoured to match the overlying plate as much as possible to avoid large bone-plate gaps. This will usually require performing closing ostectomies (wedge) on the bone flap. The individual segments should not be less than 2.5 cm in length.
Replacement of reconstruction plate
The plate is replaced and fixed in the preplanned position taking care that the proper length screws are used.
The patient's occlusion is verified to ensure proper occlusion.
Fixation of the bone graft
Locking screws are placed in a monocortical fashion to secure the bone graft to the overlying mandibular reconstruction plate.
Alternatively, the trimmed bone flap may be fixated to the plate on the side table prior to inserting the plate.
Revascularization of flap
The detailed procedure for the revascularization is outside the scope of this surgery reference.
However, in short the procedure consists of the following steps:
Appropriate recipient vessels are selected in the neck and dissected so as to be available for anastomosis
The recipient and the donor vessels adventitia are cleaned under a microscope
Appropriate vessel geometry is assured and the vessels are placed into a microvascular clamp and anastomosis carried out using 9-0 nylon sutures
Vascularization is restored after both arterial and venous anastomoses are completed
Insetting of flap soft tissue
The skin/soft tissue component of the flap is rotated into its preplanned position in the oral cavity with care not to create undue torsion or tension within the pedicle.
The skin can be rotated either over top or underneath the neomandible depending on which approach creates less tension on the skin perforators.
The skin of the flap is closed directly to the oral mucosa with interrupted absorbable sutures in a vertical mattress fashion (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.
The transected suprahyoid and floor of the mouth muscles should be re-suspended to the new mandibular symphysis eg, with sutures to the free holes in the plate. Care must be taken in avoiding damage or compression of the free flap pedicle during this maneuver.
Alternatively a hyoid suspension suture may be used to elevate the larynx and to maintain normal deglutition and avoid aspiration.
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.