CHIN AUGMENTATION AND GENIOPLASTY DONALD J. ANNINO, JR, MD, DMD The position of the chin plays an important role in facial esthetics. It can be modified in two ways. The first is by adding material to it and the second is by a horizontal sliding osteotomy. They both have their indications and limitations. The horizontal sliding osteotomy is the most versatile, however, and should be a part of the armamentarium of all facial plastic surgeons. The position of the chin is important in establishing correct facial proportions. The chin gives the appearance of strength to the face. It should not be too shallow or too deep. Absolute measurements are not as important as the facial proportions. Facial balance is critical for good facial aesthetics. Anatomically, the chin is considered as the area below the labiomental crease. However, this can be hard to determine; therefore most surgeons consider the entire lower-lip-chin complex when they evaluate facial balance and aesthetics. In the frontal view, the ideal length of the upper lip should be half the distance from the stomion to the menton. Also stated as the lower lip and chin complex is two thirds the lower portion of the face. The lower facial height (from the subnasale to the menton) should be 57% of the total facial height from the nasion to the menton. Analysis of the chin aesthetics should be three dimensional and involve the anteroposterior, transverse, and vertical planes. This is evaluated by obtaining a detailed history and physical examination, standard facial photographs, and lateral and posteroanterior cephalograms. The dental occlusion must be carefully assessed. A genioplasty does not affect the occlusion, and some patients with significant malocclusion are more appropriately treated with orthodon- tistry and orthognathic surgery to correct their dentofacial disharmony. A cephalometric tracing is extremely helpful in predicting the amount of deficiency or excess of the chin. After cephalometric studies have been obtained there are many ways to evaluate the position of the chin. Multiple facial analyses, using cephalometric tracings, have been proposed 1-s (Fig 1). They all have their proponents. When evaluating the chin, the following general deformi- ties can be seen. The chin can be too large (macrogenia), too small (microgenia), or asymmetrical. These deformities can occur either vertically, horizontally, or as a combination of both. Two basic techniques are used to change the shape and position of the chin. The first is with the use of an implant, either autologous or alloplastic, and the second is with a horizontal sliding osteotomy. In the appropriate patients, both techniques have their place. The use of implants is common because they are easy to use and less intimidating to many physicians. Many alloplastic and autogenous materials have been used to From the Department of Otolaryngology, Tufts University School of Medicine, New England Medical Center, Boston, MA. Address reprint requests to Donald J. Annino, Jr., MD, DMD, Depart- ment of Otolaryngology,750 Washington St, Box 850, Boston, MA 02111. Copyright © 1999 by W.B. Saunders Company 1043-1810/99/1003-0010510.00/0 augment the chin. The aUoplasts include silicone, hydroxy- appetite, polyethelene terephthalate, high-density polyeth- ylene (HDPE), and polytetrafluoroethylene (PTFE). 6-8 The materials can be broken down into those that are solid and those that are porous. Solid implants such as silicone do not allow ingrowth of tissue, and the surrounding capsule that develops helps hold the implant in place. The porous implant materials are PTFE, HDPE, polyethylene tereph- thalate, and hydroxyapatite. They allow fibrovascular tis- sue growth into the implant to help secure it in position. However, immobilization is needed for a minimum of 6 weeks to allow the tissue ingrowth. In general, all implants have the drawbacks of capsule formation, underlying bone resorption, and the risk of extrusion and infection.9 In addition, the soft tissue response is less predictable than the response with a horizontal sliding osteotomy. It has been reported that up to 20% of patients will be aware of the implant's presence at all times. 1°Autogenous materials are also used and include bone and cartilage. They have the risks of resorption, infection, and the need for a second surgical site. Augmentation genioplasty can be performed with the patient under local anesthesia, intravenous sedation, or general anesthesia. There are two basic approaches for performing an augmentation genioplasty. The approach can be either via an intraoral or a submental skin incision. In either case a subperiosteal pocket is created just large enough to accommodate the implant. Care is taken to ensure the implant is centered in the midline. To be sure the implant will not migrate, it can be secured in position with two screws. The use of alloplastic material for augmentation has definite limitations. It is indicated only for patients with a true horizontal deficiency that is mild. It is not recom- mended for patients with vertical discrepancies, horizontal excess, large horizontal deficiencies, or any asymmetry. Therefore, a horizontal sliding osteotomy is the procedure of choice for most patients with horizontal and/or vertical excess or deficiency, or asymmetries. Results with the horizontal sliding osteotomy are predictable and stable, and the procedure eliminates the use of an implant. The majority of this discussion focuses on this technique. Once it has been determined that a patient's facial profile is not correct and a horizontal sliding osteotomy is consid- ered, preoperative planning is required. Cephalometric tracings are imperative. A tracing of the lateral cephalo- gram is performed, including key anatomic landmarks. A template of the tracing of the chin alone is also made and is repositioned on the complete tracing to find the correct 224 OPERATIVE TECHNIQUES IN OTOLARYNGOLOGY--HEADAND NECK SURGERY,VOL 10, NO 3 (SEP), 1999: PP 224-227