[Facial asymmetries and their skeletal component]

The diagnosis and treatment of facial asymmetries is one of the most difficult challenges in orthognathic surgery. In some cases, the involvement of soft tissue defects or, in other cases, an associated basi-cranial asymmetry can complicate the management. The influence of various components of the cephalic end in the development of the face requires a thorough clinical and radiographic examination including the overall posture of the patient. The causes are multiple: congenital, constitutional, acquired with an important esthetic, functional, and psychological and social impact. The classification of these asymmetries can only be incomplete and purely didactic because of the multiplicity of clinical forms. Two elements are mandatory for the diagnosis and surgical treatment: first, the anterior clinical and radiological "craniofacial cross" established from the midline or midplane of the face; second, the clinical and radiological orientation of the maxillary and mandibular occlusal transverse and sagittal planes. The surgical techniques are the same as in conventional orthognathic surgery except for those used for the correction of the vertical posterior dimension of the face: condylectomy, lengthening osteotomy of the mandibular ramus, costochondral graft, and free flap. The contribution of 3D vision of the facial skeleton and its possibilities of measurement have improved the assessment of skeletal structure displacement during surgery. However, traditional radiographic examinations are still useful for pre and postoperative comparison and also to assess results. Computer simulation and computer-assisted surgery should allow achieving better and more stable results because of their reliability and easy access.