What Is Mandibular Distraction Osteogenesis?

Mandibular distraction osteogenesis is a surgery to increase the length of the jawbone.

Distraction osteogenesis is also called callotasis, callus distraction or osteodistraction. It is a surgical technique performed in babies to increase the length of the jawbone (mandible). It is done in newborns with a small jaw (micrognathia), which causes breathing difficulty. This surgery is called mandibular distraction osteogenesis.

Distraction osteogenesis is indicated in the following cases:

• Mandibular retrognathia is one of the most common craniofacial deformities. In this condition, the lower jaw is set further back, giving the appearance of a severe overbite. Mandibular retrognathia can be congenital (born with it) or acquired. Congenital causes include hemifacial microsomia, Treacher Collins syndrome, Pierre Robin Syndrome, Goldenhar syndrome, Nager syndrome, and mandibular hypoplasia. Acquired causes of mandibular retrognathia include trauma or previous surgery performed for developmental cysts or tumors.
• Patients who have unilateral hypoplasia (underdevelopment) of the mandible (for example, hemifacial microsomia)
• Non-syndromic mandibular hypoplasia
• Mandibular transverse deficiency
• Patients with severe obstructive sleep apnea (OSA)
• Mandibular hypoplasia due to trauma and/or ankylosis of the temporomandibular joint
• Mandibular continuity defects following surgical removal of tumors and/or aggressive cysts
• Mandibular angle deformity

There are no absolute contraindications to this surgery. However, some relative contraindications include the following:

• Patients who are unable (due to overall health or underlying medical conditions) or unwilling to undergo surgery.
• The surgery can be done in babies as young as 9 days old, but the surgery is more challenging in those who are younger than 6 years of age.
• Patients with an inadequate bone structure.
• Patients who have received prior radiation therapy may have delayed wound healing.
• Older patients may have impaired bone healing at the distraction site.
• Patients who have metal allergies.

The surgery is performed under general anesthesia (the patient sleeps during the procedure). In both distraction osteogenesis and traditional procedures, the surgeon makes a cut in the mandible bone, which is also called osteotomy (meaning cutting the bone). In traditional surgery, the doctor uses bone grafts to lengthen the bones or hold them in their new position with metal plates and screws. In distraction osteogenesis, a surgeon attaches a device called a distractor to the cut bone. The distractor may be placed under the skin or attached to the child’s skull and facial bones over the skin. The children are typically able to sleep with the devices. The devices are made of an inert, lightweight, and hypoallergenic metal, titanium. They are approved by the United States Food and Drug Administration. The type of distractor used depends on the bones that need to grow.

After surgery

During the first two to three weeks after surgery, the parent or caregiver turns one or more screws on the distractor one to two millimeters every day at home, as instructed by the doctor. This is done to keep the tension on the wires that helps move the facial bones apart. The new bone then grows to fill in the gaps. The new bone is usually soft initially and hardens over time. Once the bones are in the right position, the turning stops, and the bones heal in the new positions. This is called consolidation or the "healing phase," which takes around 1-2 months. The child would have to be on a soft/semi-solid diet until the detractor is removed. They will need to follow up with the surgeon regularly. When the new bone is strong enough, the distractor is removed by performing a short second surgery. It can take up to 6 months or longer for complete recovery.

The advantages of mandibular distraction osteogenesis over traditional mandibular osteotomies include the following:

• There is a decreased need for bone grafting for large (greater than 10 millimeters) mandibular advancements.
• There is less donor site morbidity, scarring and potential for infection.
• The procedure can be performed in babies and children.
• There is a need for tracheotomy in newborns and infants.
• It can be performed in three dimensions, namely, advancing, widening and increasing the vertical height of the mandibular bone, and it can be customized for each patient.
• There is greater patient acceptance.
• There is a decreased risk of a relapse.