Sliding Genioplasty
Edward W. Chang
INTRODUCTION
Patients seeking advice about facial cosmetic surgery often focus on structures such as the nose, the eyes, and the laxity of their skin, while the surgeon’s assessment frequently identifies areas of the face that could be surgically modified to improve overall appearance and harmony. When considering facial augmentation, the lower third of the face can have a profound influence on other facial structures, such as the nose. The smaller the chin, the larger the nose appears, and augmenting the chin gives the nose a diminished appearance (Fig. 35.1). These relationships are critical to facial symmetry. The patient profile can be significantly altered with chin augmentation, which can have significant effects on the overall facial aesthetics.
Surgical goals include creating an aesthetically pleasing facial contour and establishing proportionate facial height. This may entail the reduction of a prominent chin or the augmentation of a poorly projected chin. Ideally, the augmentation procedure should be performed with minimal morbidity.
Several surgical options exist for the augmentation of the chin. Alloplastic implants and the sliding genioplasty are the most common methods of augmentation. While both modalities may be used in chin augmentation, the sliding genioplasty has the advantage of changing the vertical height of the chin, correcting asymmetry of the chin and reducing chin projection. In the sliding genioplasty, the cut segments of bone can be moved to a new position and rigidly fixated. This can be performed alone, or used along with placement of autologous bone grafts. The sliding genioplasty is technically demanding, and is time consuming, but yields excellent cosmetic results.
In the 1940s, surgeons started using various osteotomy techniques to address the retruded mentum. Currently, the sliding genioplasty is performed by several surgical specialties. Correction of poor projection of the mentum is desirable in approximately 20% of patients undergoing rhinoplasty and about 25% of patients having a rhytidectomy. However, the patient often must be educated that this deficiency exists and that, with appropriate surgery, an overall balanced cosmetic result may be achieved.
In general, alloplastic implants are not technically demanding and have a low complication rate. Furthermore, these implants may be placed easily under local anesthesia. This well-accepted technique is generally used in the correction of the chin that has only mild-to-moderate microgenia and a shallow labiomental fold.
The sliding genioplasty has been reported to have similar rates of success. Additionally, this technique can address abnormalities in three dimensions of asymmetry, including vertical microgenia with and without retrogenia as well as vertical macrogenia with retrogenia and prognathia, making it a more versatile procedure (Fig. 35.2).
 FIGURE 35.1 The position of the chin has a profound influence on the perceived projection of the nose. Only the chin position is changed. Notice the effect on nasal projection. |
HISTORY
A comprehensive medical and surgical history is necessary in all patients. The use of a standardized questionnaire is helpful in documentation. Specific attention is given to congenital, developmental, and traumatic events involving the face, in particular the facial skeleton and teeth. Discussions with regard to dental alignment, corrective interventions, and temporomandibular joint disorders are reviewed as well. A listing of all medications, vitamins, and supplements is made to determine risks of bleeding. Drug and anesthetic allergies/intolerances are also noted. A social history of tobacco use, alcohol consumption, and illicit drug use is obtained.
PHYSICAL EXAMINATION
The preoperative consultation should include a complete history and physical examination, including dental evaluation, along with standard facial photographs. Assess asymmetry in the transverse dimension by using standard photographs on frontal view. Asymmetry may exist for various reasons, and it is crucial to appreciate asymmetry preoperatively. Asymmetry in the chin can be corrected easily with an offset (transverse) sliding genioplasty.
 FIGURE 35.2 Versatility of the sliding genioplasty; treats abnormalities in three dimensions. |
INDICATIONS
When facial analysis identifies a patient’s profile with facial disharmony in the lower third of the face, one must determine whether there is an underlying dental and skeletal deformity or if the mentum (chin) is merely under- or overprojected. When the poor projection is skeletal in nature, the situation is considered an Angle’s Class II skeletal deformity. Angle’s skeletal classification is based on the relational position of the upper and lower first molars (Fig. 35.3).
In retrognathia, the mesiobuccal cusp of the maxillary first molar is mesial (or anterior) to the buccal groove of the mandibular first molar. If only a hypoplasia of the mandible exists, the term micrognathia is more accurate and should be used. When there is no skeletal malformation, the terms for a recessed chin include retrogenia, microgenia, retruded chin, hypoplastic mentum, and horizontal mandibular hypoplasia. In chin augmentation, genioplasty usually implies an osseous movement, whereas mentoplasty suggests the use of an alloplastic implant. However, the two terms currently are used synonymously.
CONTRAINDICATIONS
There are few situations that would preclude the use of a sliding genioplasty. Severe dentoskeletal deformities will generally require more than just advancement of the chin and will require consultation for one with expertise in this field. Additionally, the teeth and mandibular height may not be favorable for an osteotomy to be performed. When considering a mandible reduction or a sliding osteotomy, carefully evaluate the teeth and the height of the mandible prior to surgery. Having long teeth with a short mandibular height is a relative contraindication for an osseous genioplasty or aggressive bone reduction. Imaging, which may be plane films or CT, will help to define issues that would dissuade the surgeon from the use of the bony genioplasty.
PREOPERATIVE PLANNING
For a sliding genioplasty, dental occlusion and skeletal structures are evaluated with the aid of preoperative photography as well as a lateral cephalometric soft tissue study and panoramic radiographs. The cone beam CT is also useful in accessing the bony anatomy of the face. Dental models should be fabricated and are used to evaluate the patient’s dental and maxillofacial situation. Functional and cosmetic goals should be discussed with the patient.
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