Distraction osteogenesis can be performed in 3 dimensions, that is, advancing, widening and increasing the vertical height of the basal mandibular bone.
Distraction osteogenesis is a feasible treatment option for children and adults with unilateral or bilateral mandibular deformities.
To illustrate the principles of this procedure we will show the lengthening of the mandibular ramus.
Distractors can be placed free-hand without any guides, but may produce unpredictable results. This section will therefore describe a more predictable approach using computer-assisted planning.
Planning is carried out virtually using a 3D-CT scan and appropriate software.
An estimate can then be made of the amount of distraction required and the bone stock available. This is helpful in deciding which distractor to use.
The virtual distractor is selected and placed on the mandibular ramus. A horizontal osteotomy is marked above the lingula. The virtual osteotomy is completed and the distractor virtually activated. If the movement is not satisfactory, the virtual distractor position can be adjusted until the desired vector is achieved.
A guide can be fabricated which allows the accurate positioning of the distractor and the osteotomy. Intraoperative navigation can achieve a similar result.
The surgical guide is positioned and stabilized with one screw. The holes for the distractor screws are drilled and the osteotomy line marked on the bone.
The guide is removed and the osteotomy completed. Care should be taken not to injure the internal maxillary artery and the inferior alveolar neurovascular bundle.
The distractor is placed and stabilized in the preplanned position using screws in the previously made screw holes.
The distractor is activated to ensure that it is working properly and is then deactivated (returned to starting position).
The wounds are then closed with a dressing applied to the external port.
After a suitable latency period, the ramus is distracted at a rate of 1.0 mm per day.
Physical therapy and mandibular mobilization should be encouraged early in the postoperative period.
Weekly review of the patient is valuable until such time as the required distraction has been achieved.
After reaching the desired distraction the device is left in place to retain the distraction and to allow for bone consolidation.
It is valuable to check that distraction is progressing well periodically with radiographs.
Consolidation will take approximately 8 weeks and the regeneration of bone into the distraction gap can also be verified with radiographs. When sufficient bone is present in the gap, the distraction device is removed.
6. Aftercare following distraction osteogenesis
Apply ice packs (may be effective in a short term to minimize edema).
The sterile dressing placed over the skin incisions is maintained for a minimum of 48 hours. Thereafter routine wound care should be instituted around the activation rod.
Antibiotic prophylaxis is continued for 1-5 days depending on the nature, complexity, and duration of the surgical procedure.
Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. A small soft toothbrush with toothpaste should be used. Antiseptic rinses can be used in the early postoperative period. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions to prevent wound dehiscence in the early postoperative phase.
Early post-operative x-rays are obtained to verify correct device placement. Additional postoperative imaging is performed as needed.
Remove sutures from skin after approximately 5 days if nonresorbable sutures have been used.
Regular follow up examinations to monitor healing and the postoperative occlusion are required.
Avoid sun exposure and tanning to skin incisions for several months.