الفهرس 
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Abstract
Possible causative factors for facial asymmetry include genetics, birth molding, cogenital and developmental deformities, abnormal growth, tumors, or other pathology of facial structures and jaws, temporomandibular joint pathology, tempromandibular joint and jaw positional changes, trauma, neurologic or neuromuscular disorders or pathology, and iatrogenic injury.
Hemifacial microsomia is one of syndromes that can cause facial asymmetry but is one of the more common syndromes seen. It is also known as Goldenhar syndrome. The condition usually occurs unilaterally but can occur bilaterally. Hypoplasia or aplasia of the mandible and condyle as well as hypoplasia of the maxilla, zygomaticoorbital complex, and temporal bone contribute to the facial asymmetry. Ear, eye and vertebral anomalies are common. With growth the facial deformity or asymmetry and malocclusion usually worsen.
Temporomandibular joint ankylosis is a common cause of acquired mandibular deformity in children. It can be caused by trauma or infection being the commonest in the pediatric age group. Long standing temporomandibular ankylosis leads to damage of the condyle with deficiency of the madibular body and ramus. Trismus in these patients can be managed by condylectomy or gap arthroplasty or by costochondral graft interposition. While a satisfactory mouth opening can be achieved with all these methods, the mandibular deformity needs separate treatment.
Surgical repair of craniomaxillofacial anomalies has traditionally involved extensive dissection, osteotomies, bony repositioning, and bone grafts to fill osteotomy gaps or to augment contour deficiencies. Conventional skeletal correction often requires multiple operations during periods of facial growth, harvesting of autogenous bone grafts with associated donor site morbidity, periods of IMF, and prolonged recovery periods usually relative to the magnitude of the surgical procedures. In addition, skeletal relapse is proportionate to the magnitude of skeletal expansion because of resistance of the soft tissue envelope.
Distraction osteogenesis has become an increasingly popular procedure in recent decades for craniofacial malformations. In 1989, McCarthy et al. first reported successful mandibular lengthening by gradual distraction. Since then, mandibular distraction osteogenesis has become a reliable procedure in the management of mandible defects, and the success of this treatment has been well documented.
Ortiz Monasterio and Molina, and Choi et al did mandibular distraction through an intra oral approach. Cohen introduced an intraoral distractor to avoid external scarring.
Ortiz Monasterio et al, introduced the technique of simultaneous bimaxillary distraction osteogenesis using an incomplete Le Fort I maxillary osteotomy, and mandibular corticotomy to maintain a stable dental occlusion.
Bimaxillary distraction is indicated in patients with facial asymmetry and a canted occlusal plane. Simultanous mandibular and maxillary distraction will correct the facial asymmetry without disturbing the pre existing compensated dental occlusion, and so save the patient need for prolonged and difficult orthodontic treatment.
In the period from January 2012 to January 2015, we treated fourteen patients with skeletal facial asymmetry (due to hemifacial microsomia and long standing TMJ ankylosis), by simultaneous bimaxillary distraction osteogenesis, 8 of them by extraoral device and 6 by intraoral device.
The preoperative assessment included clinical examination (measuring the distance from lateral canthus to the oral commissure on both sides of the face and getting the difference), radiological evaluation, cephalometric evaluation (orthodontic cephalometric tracing by measuring the distance from interorbital plane to the intergonial plane bilaterally and getting the difference, this difference gives the amount of the distraction needed to reach the facial symmetry state .an orthodontist assisted the maxillofacial surgeon in the preoperative preparation of the patients.
In our technique, we first applicate stable arch bars, then standard LeForte 1 osteotomy is done with complete mobilization of the maxilla without down fracture of the maxilla, then mandibular osteotomy is done, then fixation of the distractor, followed by IMF.
The follow up period ranged from 6 months to 24 month to evaluate the technique and detect the possible complications, cephalometric analysis was done after completion of the planned amount of distraction and after 6 months follow up.
This technique (using both types of distractors), successfully corrected the facial asymmetry, eliminated the occlusal canting, corrected the position of the chin (however two patients needed additional genioplasty), with preservation of the preoperative compensated occlusion
Both the extraoral and the intraoral distractors were effective for the technique of simultaneous bimaxillary distraction osteogenesis, but the intraoral device has many advantages over the extraoral device and eliminated a lot of its problems such as causing less discomfort to the patient, being hidden intraorally less annoying to the patient, doesnot interfere with the patient daily activities ,avoid pin tract infection and facial scarring, easy intraoperative fixation but the intraoral devices lenthen the mandible in only one direction (unidirectional distractors) and need a second stage surgical interference for removal of the distractor.