Rim mandibulectomy is a form of partial mandibulectomy. It is used to resect oral malignant tumors that are fixed to the mandibular periosteum but do not invade the mandibular cortex. It provides an oncologically sound margin for these tumors.
Mandibular marrow invasion by malignancies usually requires segmental mandibulectomy.
The vast majority of most oral cavity tumors are squamous cell carcinoma, that arise in the mucosa. Therefore the treatment of most early oral cavity tumors involve only the dentoalveolar and/or the inner aspects of the mandible.
Rim mandibulectomy is used primarily for the treatment of superficial malignancies involving the gingival alveolar mucosa.
Patient is placed in supine position and prepped and draped in the normal sterile fashion.
A bite block is placed between the molar teeth on the contralateral side of the tumor and an oropharyngeal packing is put in place.
A self-retaining cheek retractor is placed. A suture is placed in the anterior tongue to facilitate retraction. A tongue retractor may also be used.
Defining the margins of the partial mandibulectomy
The tumor is visualized and 1.5 cm margins are marked (eg. with a electro cautery) around all visible or palpable tumor.
Extraction of teeth in osteotomy line
The teeth in the line of the mandibulectomy are extracted otherwise the osteotomy will traverse the tooth roots.
3. Resection of the tumor
Soft tissues are retracted around the incision to the subperiosteal plane and the mental nerve is identified as it exits the mental foramen.
Bone cuts are now carried anterior, posterior, and inferior to the tumor using either an oscillating saw or a rotary burr.
It is recommended that the final shape of the marginal resection has rounded edges in order to avoid pathological fracture of the mandible.
Again, care is taken to preserve the inferior alveolar nerve if at all possible.
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.
An inferior rim remnant of at least 10 mm, and preferably 15 mm, is necessary to allow continuity and avoid a pathologic fracture. If such a remnant cannot be maintained, the use of a protection plate or segmental mandibulectomy with bone flap reconstruction must be considered.
4. Wound closure by skin graft
The proposed graft donor site is chosen eg. thigh, and prepped and draped in a normal sterile fashion. The area of skin to be harvested may be infiltrated with local anaesthetic with epinephrine for hemostasis and postoperative analgesia.
A dermatome is used to harvest a split thickness skin graft that will cover the defect. Hemostasis of the donor site is obtained and the wound is dressed with a temporary/removable nonadherent dressing.
The skin graft is now placed into the surgical defect, trimmed, and secured with a running locking absorbable suture (eg. 4-0 chromic).
A pressure bolster (usually gauze soaked in antiseptic ointment) is secured into place and removed after 72 hours.
5. Bone grafting
If bone grafting to enhance the height of the mandible is planned, it should be accomplished in a secondary setting in order to avoid the risk of graft loss and/or infection at the surgical site.
6. 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.