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:
Because of the thickness of the skin paddle with this flap, the internal oblique muscle may be used to reconstruct the mucosal defect.
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
Alternative orientations of the pedicle can be accomplished by using the contralateral iliac crest as the donor site
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 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 patient's residual iliac crest.
The bone should be contoured to the overlying 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.
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.
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.
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.
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.