Surgical Correction of Hemifacial Microsomia: Simultaneous Orthognathic and Distraction Osteogenesis Treatment. A Case Report on How This Hybrid Technique Can Correct Severe Facial Asymmetries
Introduction:
Hemifacial microsomia (HFM) is one of the most common congenital craniofacial soft and hard tissue deformities, manifesting as a unilateral underdevelopment of anatomical structures arising from the first and second brachial arches. The most salient feature is the underdevelopment of the mandible, particularly the ramus and condyle. Developmental disturbances at various times can lead to numerous presentations in size and function, which might require different treatment options. Conventional therapy for asymmetric patients with severe forms of HFM has been unilateral distraction osteogenesis. However, there has been noted relapse into facial asymmetry due to contraction of the bony segments and a lack of downward growth. With regard to avoiding such complications, we have elected to utilize both the distraction osteogenesis method and traditional orthognathic surgery, allowing us to better control vector movement of the maxillary and mandibular segments. It is our goal that by demonstrating this technique on such an extreme case of HFM, we can show that both methods can be used simultaneously to successfully correct this deformity, whereas each one individually might not have.
Patient and Methods:
A 16 year-old female with severe right hemifacial microsomia (HFM) underwent surgical correction at Loma Linda University Medical Center. Due to her large facial asymmetry and need for significant advancement she underwent a Lefort-I maxillary osteotomy and a bilateral sagittal split osteotomy (BSSO) of the mandible utilizing a hybrid approach. The maxilla was osteotomized and placed in ideal position utilizing the central incisor and external landmarks. Maxillary fixation proceeded with miniplates on the left and a Synthes alveolar distractor on the right. The mandible was then osteotomized and the patient placed in intermaxillary fixation in ideal occlusion at the anticipated final skeletal position. The left mandibular segment was fixated with 2 mm miniplates, while the Synthes curvilinear distractor was adapted across the right mandibular segments. A genioplasty was then completed to augment a horizontal lower facial deficiency. The patient was then released from intermaxillary fixation and the distractors de-activated. The maxillary and mandibular distractors were activated one week postoperatively with maxillary distraction continuing for 2.5 weeks at a rate of 0.5mm per day and mandibular distraction for 4 weeks at a rate of 1mm per day. Distractors were removed 6 months later, and no additional fixation was required.
Results and Conclusions:
The use of unilateral distraction osteogenesis to correct facial asymmetry in syndromic patients has been well documented and established. Unfortunately, the tendency for the patient to return to their pre-operative asymmetry still exists. In extreme asymmetry cases, such as ours, we chose to combine traditional orthognathics with unilateral distraction osteogenesis. By maintaining the position of the contralateral segment (left side) with traditional orthognathics, we were able to more effectively use and control the vector forces of the distractor segment on the hypoplastic side (right side). We hope that we have been able to demonstrate the ability of this hybrid technique to give a more optimal outcome for severe facial asymmetries than either traditional distraction osteogenesis or orthognathic surgery alone.
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