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
Restoration of a functional temporomandibular joint
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 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.
In rare cases, a locking plate with condylar head prosthesis is necessary to restore the vertical height of the ramus and to prevent malocclusion. This may include those times 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, care should be taken to line the glenoid fossa with a 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:
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.
Trimming of the bone graft
The necessary length of bone is determined from the resection specimen and recorded.
If the resection specimen is not intact, eg. in reconstructions for osteoradionecrosis, the reconstructed bone should reach a point distal to the plate, to the original position of the apex of the TMJ. Ultimately the distal end of the bone flap should rest against the intraarticular 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 closing ostectomies. Therefore, the periosteum should be freed from the bone resected during the closing ostectomy and retracted carefully during the bone cuts.
Stripping of excess periosteum for the closing ostectomy will put vascular supply to the segment at risk.
The bone should be contoured to the overlaying plate as much as possible to avoid large bone-plate gaps. This will usually require performing closing ostectomies (wedge) on the bone flap. If more than one ostectomy is used, 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.
The distal end of the bone graft should reach distal to the plate, to the apex of the condyle, and should rest just below the intraarticular disk. This end should be contoured, with a burr or rongeur, and covered with muscle or periosteum from the flap.
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:
In condylar reconstructions particularly, the vessels of the flap are oriented so as to exit the flap at the anterior aspect of the reconstruction. This avoids kinking the vessels within the temporomandibular joint region and also provides an adequate length to reach the recipient vessels.
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.
In most oral cavity defects, the oral mucosa is closed directly to the skin of the flap with interrupted absorbable suture 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 fistulae.
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.