Le Fort III Monoblock - Distraction osteogenesis

Cardinal features of the Syndromic cranial synostosis are:

• midface hypoplasia
• exorbitism
• forehead retrusion

Most of these patients have bicoronal synostosis but multiple cranial sutures in different combinations may also be involved.

Most children therefore undergo frontal/superior orbital rim advancement in infancy with repeat advancement as needed. For the midface deformity, a Le Fort III or monoblock osteotomy is required.

A monoblock osteotomy done transcranially is utilized when the forehead orbits and midface all require a similar magnitude of advancement.

The "standard" Le Fort III osteotomy is performed when the superior orbital rim and forehead are in a satisfactory position and only the midface requires advancement.

The Le Fort III osteotomy using conventional fixation and bone grafts is usually performed after craniofacial growth is complete, although some proponents do it during the period of growth.

More often the Le Fort III osteotomy is done via distraction osteogenesis in the younger patients in order to overcorrect the deformity, reduce complications, obviate the need for bone grafts, and hopefully therefore reduce the total number of operations the child might need.

The conventional monoblock osteotomy can also be done as a single stage or…

…via distraction in children up to age 6-8 years. Single stage advancements are not often done after this age due to the excessive risk of complications (infections, CSF leak, etc.).

The decision to use either an internal buried device or an external halo should already have been made after careful discussion with the family.

External halo distractors are cumbersome and may be more easily dislodged, may leave scars at the temporal attachment and may penetrate the skull if there is direct force on the device. However, they allow for multiple vector distraction, and do not require a large second operation to remove.

Internal distractors are less cumbersome with less chance for dislodgement and injury and are well suited to an active lifestyle. However, they are only single vector devices, require second operations to remove and have a greater risk of infection.

The patient is placed in a supine position on a well-padded headrest.

The osteotomy is approached through a coronal incision with or without an upper buccal sulcus incision. Extensive dissection of the orbit (deep orbit, anterior and posterior to medial canthus which remains attached), zygoma, midface, and nose is required.

Some surgeons use a lower lid incision as well, but if this can be avoided fewer complications of lid malposition will result. Similarly the osteotomies can usually be done without a buccal sulcus incision.

The following pages provide general information regarding orbital anatomy and dissection

• Preoperative considerations
• Anatomy of the bony orbit
• Correlation of surface and cross sectional anatomy
• Introduction to periorbital dissection
• Orbital floor dissection
• Medial orbital wall dissection
• Lateral orbital wall dissection
• Orbital roof dissection
• Adjunctive access procedures (orbitotomies)
• Retrobulbar hemmorage

After the exposure of the forehead and the orbits, a bifrontal craniotomy beginning 1 cm superior to the superior orbital rim and extending to behind the coronal sutures is outlined.

Burr holes are first placed at the vertex, avoiding the sagittal sinus, and nasal frontal region as well as temporally. An epidural dissection between these points is made.

The neurosurgeon then completes the osteotomies using a craniotome.

After the bone flap is removed, the dura is freed from the anterior and middle fossae in an epidural plane.

The dura is protected with neurosurgical cottonoids.

Malleable retractors are used intracranially to retract and protect the dura and intraorbitally to protect the orbital contents when performing the osteotomies.

Vertical osteotomies are made just behind the lateral orbital rims and down through the lateral orbital wall.

A vertical osteotomy using a saw at the junction of the zygomatic arch and zygomatic body is completed.

With the brain carefully retracted, a right angle saw is turned intracranially and the orbital roof is osteotomized beginning at the lateral wall osteotomy and ending at the cribriform plate.

An osteotome is inserted from intracranially and the medial orbit is osteotomized behind the canthus and on to the medial floor.

An osteotome is used to perform osteotomies across the orbital floor anterior to the inferior orbital fissure, connecting to the medial wall osteotomies.

The osteotomy through the pterygomaxillary junction is completed with a curved osteotome from the infratemporal fossa or transorally if an upper buccal sulcus incision has been made.

To assure that the osteotome does not hit vital structures, one usually guides the direction of the osteotome with one hand while a palpating finger is placed medially at the posterior edge of the palate.

The final osteotomy is made from intracranially and goes from the cribriform plate through the posterior septum to the level of the palate.

It is safest to place a finger in the mouth at the posterior palate to assure the osteotome does not go too deep or penetrate the mucosa.

Disimpaction forceps are then introduced and the monoblock segment is down and out fractured mobilizing it completely.

In monoblock distraction, new bone forms in the cranial base and at the osteotomy sites as the face is brought slowly forward. Unlike a single stage monoblock procedure, where one leaves a large connection between the anterior cranial base and the sinuses which requires a galea flap and sealants, no special treatment of this area is required.

If one is using a halo device, fixation to the midface is gained through either:

• occlusal splint with outriggers
• direct screws to the maxilla either at:
  - the pyriform aperture
  - the zygomatic region
  - both pyriform and zygomatic regions

Direct screws to the maxilla require the addition of an upper buccal sulcus incision.

If attached to the teeth or zygoma, a heavy bent rod exits the mouth and wraps around in front of the lip and will be attached the halo at this point. If the pyriform plates are used the pins exits transcutaneously near the alar rim, on the cheek or lip skin, or just outside the nostril.

A second point of fixation is made at the superior orbit. Fixation screws with pins that exit the skin are applied.

The frontal bone flap is replaced and affixed to the monoblock segment with titanium plates.

Following closure of the wound of the coronal incision, the halo device is affixed to the skull temporally by a series of pins, usually 5 on each side. It is positioned so that the transverse bar is at the level of the brow and the vertical bar is in the midline. It should be stable enough to lift the patients head off the table without shifting.

Wires then attach the screw arms of the distractor to the midface anchoring component(s). They should not be over tightened.

Distraction is usually begun at postoperative day 5 at a rate of 1 mm/day. As the midface is brought forward the device may be adjusted to change the occlusal cant vector or pull more to the right or the left to optimize the resulting occlusion.

Children
In children in the middle years, over distraction to Class II relationship is advised to accommodate future mandibular growth.

Adults
In adults, distraction is usually performed to attain Class I relationship and is aided by orthodontic elastics to guide the maxilla into the proper occlusion with the mandible (docking the occlusion).

Following the completion of distraction, the halo device is left in place for 1-3 months to allow for consolidation of the regenerated bone and is then removed. If an occlusal device is used this may be removed in an office setting without anesthesia. General anaesthesia is usually indicated when pins and plates in the maxilla must be removed. The pins in the superior orbit are usually just removed percutaneously and the plates left behind.

If one has chosen an internal distraction device, it is adapted to the zygoma and the stable temporal bone and affixed here with screws (1.5-2.0 titanium). The device is tested to be certain that it is functional. As it is a single vector device, one must be certain that the desired position fits the vector chosen. Generally in the younger patients this is a straight AP vector to avoid vertical elongation of the orbit. Although, an anterior open bite may develop this can be closed later in life or may self-correct.

The activation arm of the distractor is brought out through the coronal incision or through a separate stab wound.

The frontal bone flap is replaced and affixed to the monoblock segment with titanium plates. (See illustration to the left).

Distraction is usually begun at postoperative day 5 at a rate of 1 mm/day. In children in the middle years, over distraction to Class II occlusal relationship is advised to accommodate mandibular growth. In adults, distraction is usually to attain a Class I occlusal relationship.

Following the completion of distraction, the device is left in place for 1-3 months to allow for consolidation of the regenerate bone and is then removed. This may require a complete re-opening of the coronal incision and removing the device from both the temporal region and the advanced midface. Some devices do not rigidly affix to the midface but rather are adapted without fixation to the posterior edge of the zygoma and may be removed with less extensive dissection.

Most patients with Syndromic synostosis have canthal malposition so a lateral canthopexy in an overcorrected superior position is completed prior to closure.

Most surgeons favors placement of a bulb suction drain under the scalp for 3-5 days. Resorbable skin sutures are often used.

A circumferential head dressing is utilized for 48 hours. The neurosurgeon may request placement of a lumbar drain if significant dural tears have occurred during surgery. Patients should spend at least 1-2 days in an intensive care unit for neurological monitoring.

Keeping the patient’s head in an upright position postoperatively may significantly improve periorbital edema and pain. Some surgeons use injectable corticosteroids during surgery to reduce periorbital swelling.

To prevent orbital emphysema, nose-blowing should be avoided for at least 10 days.

The following perioperative medications are controversial. There is little evidence to make strong recommendations for postoperative care.

• Avoidance of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs) for 7 days.
• Analgesia as necessary.
• Antibiotics (many surgeons use perioperative antibiotics. There is no clear advantage of any one antibiotic, and the recommended duration of treatment is debatable.).
• Nasal decongestant may be helpful for symptomatic improvement in some patients.
• Steroids may help with postoperative edema. Some surgeons have noted increased complications with perioperative steroids.
• Ophthalmic ointment should follow local and approved hospital protocol. This is not generally required in case of periorbital edema. Some surgeons prefer it. Some ointments have been found to cause significant conjunctival irritation.
• Regular perioral and oral wound care has to include disinfectant mouth rinse, lip care if intraoral incision has been used.

Postoperative examination by an ophthalmologist may be requested, although sever periorbital edema may prevent useful assessment. The following signs and symptoms are usually evaluated:

• Vision
• Extraocular motion
• Diplopia
• Globe position
• Lid position

Postoperative imaging has to be performed within the first days after surgery to verify accuracy of surgery. 3-D imaging (CT, cone beam) is recommended.

Remove sutures from skin after approximately 7-10 days if nonresorbable sutures have been used.
Apply ice packs for the first 12 postoperative hours as able although infants and young children do not tolerate this well (may be effective in a short term to minimize edema).
Avoid sun exposure and tanning to skin incisions for several months.

Soft diet can be taken as tolerated until there has been adequate healing of any maxillary vestibular incision. In children and infants age appropriate diets are then prescribed.
Patients in MMF will remain on a liquid diet until such time the MMF is released.

Clinical follow-up depends on the complexity of the surgery, and whether the patient has any postoperative problems. Most patients are discharged at postoperative day 3-5 and seen again in 2-3 weeks.

• In patients undergoing monoblock or Le Fort III distraction, distraction typically begins at day five at 1 mm/day and is assessed weekly with plane radiographs and clinical examination until the desired position is reached. After advancement a period of consolidation of 1-3 months is recommended before the retractors are removed.
• In patients undergoing conventional advancement with intermaxillary fixation, MMF is kept in place for 4-6 weeks. Routine oral hygiene is prescribed. Patients with arch bars and/or intraoral incisions and/or wounds must be instructed in appropriate oral hygiene procedures. The presence of the arch bars or elastics makes this a more difficult procedure. A soft toothbrush (dipped in warm water to make it softer) should be used to clean the surfaces of the teeth and arch bars. Elastics are removed for oral hygiene procedures. 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. A Waterpik® is a very useful tool to help remove debris from the wires. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions as this may lead to wound dehiscence.

The patient needs to be examined and reassessed regularly and often. Additionally, ophthalmological, ENT, and neurological/neurosurgical examination may be necessary. If any clinical signs for meningitis or mental disturbances develop, professional help has to be sought. Due to the young age of many patients, routing CT-scans are performed only if clinically indicated to avoid excessive radiation exposure.