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 mandibular continuity
Restoration of dentition
Restoration of chewing (mastication) and swallowing (deglutition)
Restoration of facial contour
Consistently obtain a healed wound
Reconstruction of a functional temporomandibular joint
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, with or without a condylar prosthesis
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 lateral 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, the patient is placed in occlusion and MMF is established with either arch bars or rapid MMF screws between the maxilla and the non-diseased mandible.
Alternatively a custom made 3D-model of the mandible is made. This model is then used to shape the plate.
In rare cases, a locking plate with a condylar head add on prosthesis may be used to reconstruct the TMJ and restore the vertical height of the ramus. This may include those instances when the bone flap is not long enough to reach the glenoid fossa, eg. defects greater than the hemi mandible, or when the bone shape does not allow creation of a neo condyle, eg. scapula.
The use of a TMJ prosthesis is controversial because of the occasional incidence of erosion of the prosthesis into the middle cranial fossa. If the surgeon chooses to use this prosthetic alternative, great care should be taken to position the prosthetic condyle into the glenoid fossa with an interpositional soft tissue flap to prevent erosion into the middle cranial fossa.
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.
A lip split incision can be added if necessary to improve access and visualization into 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 made using a saw. Care is taken to resect a 1 cm margin of normal bone at the side of the remaining mandible.
The tumor is visualized intraorally 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, suprahyoid muscles, 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 insertion of the lateral pterygoid muscle is detatched from the subcondylar region and the capsule of the temporomandibular joint is entered.
The condyle is retracted inferiorly and the ligaments divided, thus freeing the mandible.
Every effort should be made to preserve the intraarticular disk of the TMJ, if oncologically sound.
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.
Placement of reconstruction plate
The patient is placed in occlusion and MMF is established with either arch bars or rapid MMF screws between the maxilla and the non-diseased mandible.
An angled locking mandibular reconstruction plate template is chosen and placed on the native mandible so as to engage at least 4 screw holes. The template should be fashioned such that the portion of the plate that will reconstruct the ascending ramus should reach just inferior and lateral to the TMJ capsule. This will allow reconstructed bone placed distally, to rest just below the intraarticular disk.
a preformed mandibular reconstruction plate could facilitate this type of reconstruction
a custom made 3D-model of the mandible can be used to shape the plate.
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 shape.
The plate is placed and fixed in position with bicortical screws. The MMF can then be released.
Harvest of graft (Iliac crest-internal oblique free flap)
Because of the thickness of the skin paddle with this flap, the internal oblique muscle is used to reconstruct the mucosal defect.
The external skin of the flap is positioned so as to reconstruct the skin defect of the face/neck.
In order to position the vessels near the angle of the neomandible, the ipsilateral iliac crest is used as the donor site.
The bone should be harvested to a height similar to the native mandible to provide the best reconstruction possible. Inclusion of the bone inferiorly to the anterior inferior iliac spine will allow for creation of a neocondyle.
Alternative orientations of the pedicle can be accomplished by using the contralateral iliac crest as the donor site.
Trimming of the bone graft
The harvested bone graft is now measured against the mandibulectomy defect. The bone should extend distal to the ascending portion of the mandibular plate and rest just below the intraarticular TMJ disk.
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 osteotomies. The pedicle is adherent to the inner aspect of the iliac crest and therefore the osteotomy is carried out lateral to medial. The saw should barely penetrate the inner bony cortex when making the cut.
This technique creates an open osteotomy when the bone is inset to the plate and this can be packed with cancellous bone harvested from the patients residual iliac crest.
The bone should be contoured to match the overlaying plate as much as possible to avoid large bone-plate gaps. This will usually require performing osteotomies on the bone flap. The individual segments should not be less than 2.5 cm in length.
The neo condyle can be reshaped to mimic the shape of the resected condylar head.
Fixation of the bone graft
Locking screws are placed in a monocortical fashion to secure the bone graft to the overlying mandibular reconstruction plate.
The distal end of the bone graft should reach distal to the plate, to the apex of the TMJ, and should rest just below the intraarticular disk. This end should be contoured, with a burr or rongeur to mimic the resected condyle, and covered with muscle or periosteum from the flap.
Alternatively, the trimmed bone flap may be fixated to the plate on the side table prior to inserting the plate.
Once fixation is complete, the neomandible should be suspended from the root of the zygoma with a permanent suture to maintain its position within the joint space.
Postoperative MMF for 7-10 days could be helpful in order to maintain the occlusal relationship during the initial healing process. Elastics are recommended for a few weeks.
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 internal oblique muscle is rotated medial to the neomandible into its preplanned position in the oral cavity with care not to create undue torsion or tension within the pedicle. In order to minimize tension, cuts can be made at the lateral edges of the muscle near its bony insertion towards the muscle perforator, with care to not disrupt the blood supply. The muscle can usually be rotated nearly 270 degrees and the distal end may be used to provide coverage of the plate.
In most oral cavity defects, the native oral mucosa is closed directly to the internal oblique fascia 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 muscle fascia is usually left to mucosalize but may be skin grafted depending on surgeon's preference.
The skin component of the flap is now positioned into the neck/face defect and closed in layered fashion.
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.