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 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 and eventually overlying skin.
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 cutaneous defects and contour
Consistently obtain a healed wound
Restoration of the oral stoma (if lip involved)
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.
When the tumor extends to the outer cortex of the mandible, the reconstruction plate cannot be fashioned by applying it directly to the mandible prior to the mandibulectomy. In this situation, special devices (ie. bridge fix) may be used to maintain the position of the proximal and distal segments in their preoperative anatomic position.
Alternatively, in the dentate patients the placement of arch bars and subsequent MMF will maintain the proper alignment of the mandibular segments.
Alternatively maxillo mandibular bridging plates (as illustrated) on the intact part of the mandible can also be used instead of the segment fixation device both in dentate and edentulous patients.
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:
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.
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 incisions 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.
Outline of the mandibular 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 to allow for placement of the segment positioning devices and subsequent application of the locking mandibular reconstruction plate. Proposed lines for mandibular osteotomy are marked.
Extraction of teeth
In a dentate patient, the teeth in the line of the osteotomies are extracted.
Given the fact that the plate adaptation using a template is not possible because of the tumor invasion, the following solutions can be applied:
Mandibulo-maxillary fixation in order to maintain both bone stumps in position. This can usually be done applying plates from the remaining mandibular stumps to the maxilla or more conventional means using arch bars.
An external fixator (eg, bridge fix) could be put in place maintaining the bone stumps in proper relationship. The external fixator should be kept in place during the tumor resection not to lose the proper position of the mandibular stumps.
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.
The tumor is visualized and palpated intraorally and 1.5 cm soft tissue margins are marked (eg. with an electro cautery) around the tumor in the oral cavity.
Removal of the bone segment and tumor
The bone is retracted inferiorly and anteriorly. Soft tissue cuts are made through the previously marked resection limits in the floor of mouth/tongue mucosa, suprahyoid muscles and the mylohyoid muscle.
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 section to ensure the adequacy of the tumor resection.
Placement of reconstruction plate
A template is contoured to the external mandible to bridge the defect, staying just superior to the inferior border of the mandible.
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.
A minimum of 3 screw holes should be placed on either side of the defect.
Note: The screws close to the resection border should be at least 5-7 mm away from the osteotomy line.
A locking mandibular reconstruction plate is chosen to bridge the defect. This should be a load bearing plate (eg. 2.4 mm). Alternatively a preshaped mandibular reconstruction plate can also be used. 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 fit.
The plate is placed and secured to the remaining mandibular segments with bicortical screws (minimum 3 on each side). After this step is accomplished, the external fixator is removed or the MMF is released.
Two skin paddles are usually required for reconstruction of this defect, one for mucosal reconstruction and one for skin coverage. In this case, the skin paddles can be harvested in both transverse and vertical orientations (scapular and parascapular respectively). The skin paddles are best harvested as a single unit and separated once the bone segment has been fixed in place.
The length of the perforators to either skin paddle allows the skin segments to be positioned well distant from the bone segment, thus allowing for a tension free closure of almost any skin and mucosal defect in the face or neck
While the scapula from either side can be used for a given defect, the ipsilateral scapula is usually chosen and the patient is placed in the lateral decubitus position. This allows for a single surgical prep with sequential harvesting of the graft.
Contouring of the bone graft
The harvested bone graft is now measured against the mandibulectomy defect.
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.
Fixation of the bone graft
Locking screws are placed in a monocortical fashion to secure the bone graft to the overlying mandibular reconstruction 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.
Revascularization is restored after both arterial and venous anastomoses are completed.
Insetting of skin/soft tissue
The skin component of the flap is now divided into appropriate sized paddles for the mucosal and skin defects. The paddles can be completely divided through skin and soft tissue but each must include its nutrient vessels to ensure survival.
One skin paddle is rotated over the neomandible into its preplanned position on the neck/face with care not to create undue torsion or tension within the pedicle. The second skin paddle is rotated into the oral cavity defect.
Closure of the intraoral defect is accomplished first, closing skin paddle to mucosa with interrupted 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.
The skin paddle is sutured to the facial skin in layered fashion using absorbable sutures eg. 3-0 Vicryl for the deep layers and nylon for the skin.
When possible, 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 to 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.