A design for midface distraction
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In the last few years, distraction techniques have been used successfully to correct the hypoplastic human mandible. In patients with cleft lip and palate, normal growth of the maxilla may be impaired by early cleft repair, and many of them do not respond to orthodontic procedures alone. Maxillary distraction is an alternative technique to correct maxillary hypoplasia during mixed dentition. In the last 3 years, the procedure was performed in 38 patients aged between 6 and 12 years; 18 patients had unilateral cleft lip and palate, 9 patients had bilateral cleft lip and palate, 7 patients had unilateral cleft palate, 2 patients had prognathism, and 2 patients had nasomaxillary dysplasia. Photographs, posteroanterior and lateral cephalograms, and dental models are obtained preoperatively (as well as an orthopantomogram) to locate the tooth buds. A subperiosteal dissection is performed exposing the anterior and lateral aspects of the maxilla, and an incomplete horizontal osteotomy is done above the tooth buds. Using a facial mask and an intraoral fixed appliance system as an anchorage, we initiate on the fifth postoperative day the application of distraction forces. Maxillary advancement between 4 and 12 mm is achieved during 3 to 4 weeks, and a satisfactory class I or II molar relationship is also obtained. A combination of forward and downward distraction forces can be used to achieve simultaneous advancement and elongation of the hypoplasic maxilla. The aesthetic results are excellent, and the nasolabial angle is increased, including a more anterior projection of the upper lip. Nasal breathing is improved as well as the air flow and patency of the nasal airway. Velopharyngeal function remains unchanged after the procedure. The follow-up in this series varied from 6 months to 3 years. No relapses have been observed.
Midface osteotomy was performed on 5 young adult sheep aged 10-12 months. In 4 animals midface advancement by gradual distraction was performed using an external device; one animal served as a control. The midface was advanced by 2 mm per day for 21 days. The amount of advancement was 36 mm in the nasofrontal area and 43 mm on the lateral aspect of the maxilla. After the period of active distraction the midface was maintained with external fixation for an additional 6 weeks to allow for ossification. Radiographs were obtained immediately postoperatively, after 21 days of distraction, and at the end of the 6 week fixation period. New bone formation in the distracted area was obvious radiographically, clinically and histologically. In conclusion, midface advancement by osteotomy and gradual distraction is possible in the sheep model and may offer controlled correction of deformity, obviating the need for the bone grafting.
A miniature system of distraction devices has been employed for maxillary-midface advancement in two children with cleft lip and palate, class III malocclusion, and associated midfacial hypoplasia. The devices are made with commercially available palatal expansion screws linked to rigid fixation plates. A midfacial osteotomy is used, and distraction is begun on the third postoperative day. In the first child, a 7-year-old boy, the midface was distracted 11 mm sagittally and 4 mm inferiorly. In the second patient, a 4 1/2-year-old girl with unilateral cleft lip and palate and midfacial retrusion, an 11-mm distraction was carried out in the vertical and sagittal direction. There were no complications, and none of the devices failed. Maxillary-midfacial distraction osteogenesis to correct severe maxillary-midfacial hypoplasia in children with clefts and other craniofacial disorders permits early intervention with potentially less invasive techniques than are currently available.
Fourteen patients underwent Le Fort III midface advancement using distraction techniques. Six have cephalometric documentation extending beyond 1 year postoperatively, and the positions of cephalometric points A and orbitale over time are reported here. Excellent stability of advancement at the occlusal level and some relapse at the level of orbitale are documented. Elimination or diminution of obstructive sleep apnea occurred in all patients so affected, and one of two patients with tracheostomy has been decannulated. Speech effects have been mild or transient. No untoward effects on extraocular muscle function have occurred.
Distraction osteogenesis of the midface offers new possibilities for the treatment of large sagittal discrepancies between the upper and lower jaws. The use of an extraoral halo-borne distractor, which allows free three-dimensional vector control, may cause problems in the connection between the midface and the distractor. To overcome these difficulties, we present a new modular retention system to gain bone anchorage whenever a toothborne appliance is not suitable. Distraction osteogenesis with an extraoral appliance is therefore possible even in edentulous elderly patients. We have used this system successfully in 11 patients.