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• Since Ilizarov's works on bone distraction and their application to craniofacial bony structures, bone distraction seems to be the only early therapeutic alternative in cases of severe dysmorphoses of the maxillofacial complex. Classically, these pathologies are treated at the end of the growth period by Lefort I-type osteotomies and osteosyntheses, with or without bone grafting, along with orthodontic treatments aiming to correct the dental arches. Numerous limitations go with this type of treatment: waiting for the end of the growth period, limits in the mandibular advancement due to a defect in bony structures sometimes ending in undercorrection, and the choice of a compromise about the aesthetic and functional result.
Then, maxillary distraction became an early treatment option for severe maxillary hypoplasia in young children.
2 - perating procedure
• Polley and Figueroa's RED System is a rigid external appliance made from a semi-circular adjustable frame, which is fixed to the parietal regions by 4 to 6 intra-osseous screws, plus a sliding vertical anterior axle on which a horizontal transversal bar with two distracting screws is affixed. This system is adjustable in the three directions of space.
• Orthodontic protocol: distraction forces are applied to the mandible through a dental anchorage system that includes two bands cemented on the first maxillary molars and connected by a double arch (0.050") and a transpalatal arch for rigidity. A pair of J-hooks is welded perpendicular to the buccal arch in both lateral incisors sectors, these hooks are running close to the lips commissures up to the palatal plane level. Each ends in a loop for the transmission of distracting forces with a metal wire. The application point of these forces is level with the palatal plane or higher, depending on the intended maxillary movement.
• The surgical protocol encompasses a no-shift Lefort I-type full osteotomy with a septal and pterygomaxillary disjunction or a Lefort II procedure.
• Distraction protocol: activation starts three days after surgery, at a rate of 1 millimeter a day, up to the intended advancement. During the active phase of the distraction, adjustments in the protraction rate or in the position of the traction direction can be made, depending on the clinical evolution. Once the intended advancement is obtained, the distractor remains in position for 2 to 3 weeks, in order to allow the consolidation to take place. After this phase, the RED will be removed and the child will wear a Delaire's mask at night for 4 to 6 weeks.
Why prefer distraction to advancement osteotomy?
Patients with an indication for distraction present a pathology of the orofacial area (sequelae of cleft palates, severe maxillary deficiency with hypoplasia or agenesis of the premaxilla), with a very important maxillary retrognathism without mandibular disorder. Virtually, these patients can not be treated by classical advancement surgery (except by bimaxillary surgery and/or bone grafting, for advancements superior to 8-10mm) and the aesthetic result can be compromised. In addition, there is a risk for a decompensation of speech problems by too strong or too fast a traction on the velopharyngeal muscles.
Lucia MATTEI, Michèle BIGORRE, Pédro MONTOYA
Pediatric Plastic Surgery Unit, CHU Lapeyronie
Figure 1 : RED System
Figure 2 & 3 : Double arch. Intra-oral and extra-oral views.
Figure 4 & 5 : Lateral view before and after distraction
A maxillary hypoplasia, when detected early, can be treated by classic orthognathic surgery only at the end of the growth period. Maxillary distraction by progressive bone lengthening provides correction, mainly in young patients but also when the maxillary hypoplasia is severe. This technique with the RED system means a tight collaboration between the surgeon and the orthodontist. Its many benefits, include the elimination of bone grafting, osteosynthesis or intermaxillary blocking; and simultaneous expansion of surrounding tissues. Correcting maxillary hypoplasia in the mixed dentition and correcting the maxillary-mandibular relationship modifies the orthodontic strategy in terms of age and philosophy. Thanks to an early correction of skeletal discrepancies, the orthodontic treatment can begin in better anatomic conditions and be completed earlier. Progressive bone distraction can answer the main concern about the correction of dysmorphoses: a functional retraining and an aesthetic improvement of the child.
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