COSMETIC        Orthognatic Surgery

Orthognathic surgery involves the surgical manipulation of the elements of the facial skeleton to restore the proper anatomic and functional relationship in patients with dentofacial skeletal anomalies.

Orthognathic surgery can be used to manage a broad spectrum of maxillofacial abnormalities, including congenital, developmental, and acquired deformities.

Historically, the ability to reposition the mandible in a stable manner long preceded the ability to reposition the maxilla. As a consequence, many patients underwent only mandibular surgery to correct a primary maxillary deformity. The specialty of orthognathic surgery did not fully develop until Obwegeser demonstrated the possibility of repositioning the maxilla in a stable consistent manner in 1965 and reported simultaneous repositioning of the maxilla and mandible in 1970.

Problem
The word orthognathic comes from the Greek word orqos, meaning to straighten, and gnaqos, meaning jaw. Orthognathic surgery thus means to straighten a jaw. Defining a straight jaw versus one that is not requires determining the degree of deviation from a specified population norm. Nevertheless, Dr. Shome firmly believes that restoring the orthognathic form of the face ultimately depends upon achieving the ideal facial esthetics of the individual patient, not simply restoring the average normative values of a population.
Dr. Shome feels that it is worthwhile to remember that the face is more than the upper and lower jaw; when deformities extend to involve the cranio-orbital skeleton, evaluation and management expand the scope of maxillofacial surgery to craniofacial surgery. Thus, orthognathic or maxillofacial surgery is a subset of craniofacial surgery.

Correction of maxillofacial deformities requires careful analysis of the soft tissue with clinical examination and supporting photographs, skeletal evaluation with standardized radiographs, and dental evaluation with study dental casts. Formulation of a treatment plan thus requires close cooperation of the surgeon working with the dentist, the orthodontist, and at times the restorative prosthodontist. Unlike many surgical procedures, outcome depends not only on the surgical procedure but also on a multitude of factors that begin long before the actual surgery as well as on control of the variables long after surgery.

Etiology
Dentofacial skeletal anomalies generally occur as a result of a differential in growth of the upper facial skeleton to the lower facial skeleton, resulting in discrepancy of the normal relationship that exists between the upper and lower jaw. Underlying genetic predisposition and acquired causes can influence the normal growth of the facial skeleton. Congenital anomalies, from syndromic conditions such as Apert and Crouzon syndromes to facial clefts, affect normal growth and development.

Traumatic events in the mature skeleton can displace the normal elements and require repositioning osteotomies if improperly reduced initially. Traumatic events in the developing facial skeleton can disturb normal subsequent growth. Other etiologies that can result in significant dentofacial anomalies include neoplastic growth, surgical resection, and iatrogenic radiation. However, of all the etiologies, developmental anomalies representing the extremes of population norms are the most common conditions requiring orthognathic surgery.

Pre-surgical Analysis and Workup          

Clinical assessment by Dr. Shome is directed specifically at evaluating the relative position and size of each of the facial skeletal elements, the degree of zygomatic projection, and the maxillary and mandibular positions in space relative to each other and to the cranial-orbital region. The nasolabial angle, upper lip length, lip competency, labial-mental sulcus, and cervicomental angle are documented. Any facial asymmetry is noted along with the relationship of the maxillary dental mid line to the mandibular dental mid line and the dental mid lines to the facial mid line. The intraoral examination focusses on the dental alignment within each arch and relationship of the dental arches to each other. The degree of dental display on repose and smile is also recorded with the amount of gingival display.

Facial balance typically is assessed by Dr. Shome by dividing the face in thirds. The upper third is from the anterior hairline (trichion) to the glabella, the middle third from the glabella to the subnasale, and the lower third from the subnasale to the menton. When each of the thirds is equal, the face is said to be balanced and of "ideal" proportions. The lower third may be further divided into an upper third (subnasale to oral commissure) and a lower two thirds (oral commissure to menton). Additionally, in profile view the face should have a slight degree of convexity as measured from the glabella to the subnasale to the menton.

Ideal facial proportions believed to be in aesthetic balance. Such proportions are only guidelines, as ideal proportions change over time, and the ideal result varies with patient expectations.

Excess facial convexity, flatness, or concavity is felt to be less than ideal. However, facial proportions are only idealized concepts and have changed over time. They merely provide a guideline that is not true for every patient; a wide range of aesthetic faces defies such absolute canons.

Profile analysis illustrating the degree of facial convexity or concavity from an acceptable orthognathic norm.

Indications

Indications for orthognathic surgery include facial dysmorphism with and without functional implications. As an illustration, an osseous genioplasty for a patient with retrogenia but without malocclusion should be considered for facial form. If the retrogenia is associated with retrognathism resulting in a malocclusion, orthognathic surgery is indicated for restoring the facial form and for functional occlusion. Airway and speech are other indications when considering the functional need for orthognathic surgery. Restoration of the normal anatomic relationship between the maxilla and mandible relative to the cranial base reestablishes the functional components (ie, form and function) of the facial skeleton.

Treatment

Surgical Therapy

The elements of the facial skeleton can be repositioned, redefining the face through a variety of well-established osteotomies, including Le Fort I-type osteotomy, Le Fort II-type osteotomy, Le Fort III-type osteotomy, maxillary segmental osteotomies, sagittal split osteotomy of the mandibular ramus, vertical ramal osteotomy, inverted L and C osteotomies, mandibular body segmental osteotomies, and mandibular symphysis osteotomies.

Most maxillofacial deformities can be managed with 3 basic osteotomies: the mid face with the Le Fort I-type osteotomy, the lower face with the sagittal split ramal osteotomy of the mandible, and the horizontal osteotomy of the symphysis of the chin.

Dr. Shome firmly belives that while alloplastic chin implants are used most commonly for correction of minimal sagittal chin deficiencies, the horizontal osteotomy of the symphysis (osseous genioplasty) is a far more versatile procedure. The chin can be repositioned in multiple planes, allowing for correction of significant sagittal and vertical deformities of deficiency (microgenia) or excess (macrogenia) and asymmetric conditions. It is important to remember though that orthognatic surgery involves major procedures and use of these procedures for aesthetic purposes should be offered only once all other less invasive choices are exhausted or not applicable in a particular patient.