The Art of Genioplasty

SELECTED READINGS IN ORAL AND MAXILLOFACIAL SURGERY TAKING ON THE CHIN— THE ART OF GENIOPLASTY Kevin L. Rieck, DDS, MD Volume 21, Number 2 July, 2013 TAKING ON THE CHIN – THE ART OF GENIOPLASTY Kevin L. Rieck, DDS, MD INTRODUCTION The chin represents one of the most recognizable structures on the human face. Numerous methods to alter the contour and appearance of the chin and lower facial esthetic subunit have been described in the past. Currently osseous surgery of the chin is utilized to provide esthetic enhancement, as an adjunct for facial balance and harmony in orthognathic surgery and as a means to provide airway improvement in patients with severe obstructive sleep apnea.1-4 This article will describe methods for facial analysis of the chin, review concepts and techniques associated with genioplasty approaches and contrast osteotomies and implants with respect to modification of the chin itself. History including various metals and non-metallic implants, such as ivory, all of which have As a surgeon I have always felt it impor- now been discontinued due to complications 7 tant to have some knowledge of the historical or poor results. In 1934, Aufricht described aspects associated with procedures we enter- the use of nasal cartilage as a means for chin 8 tain and perform for our patients. Guyuron augmentation. In 1942, Hofer had been in his textbook Genioplasty nicely outlines observing with Drs. Obwegeser and Trauner this topic.5 Historical descriptions of Egyp- and subsequently published the first article tian and Greek statues are referenced. The describing an extraoral approach to sliding 9 Egyptian statues reflect a round face with osseous genioplasty. prominent eyes, a straight nose, thick lips and a positive appearing chin. Greek statues The 1950s saw the introduction of inlay by contrast reflect an oval face that tapers bone grafts, bovine cartilage grafts, dermis to the chin and blends proportionately with grafts and some acrylic implants for genio- 5,10,11 the lower face.5 Woolnoth in 1865 published plasty. In 1957, Trauner and Obwegeser The Study of the Human Face in which he published the first article on intraoral sliding 12 describes the three facial profiles as straight, osseous genioplasty, which continues to convex and concave.6 He further indicates be used throughout the world today. Inter- that the straight face is deemed most attrac- estingly, Hofer was observing Trauner and tive, the convex youthful and the concave Obwegeser as they were exploring some of profile as older appearing.5,6 We continue to these early surgical techniques. Dr. Obwe- utilize these basic descriptions in contempo- geser was disappointed that Hofer had pub- rary facial analysis. lished the first article regarding genioplasty but comments that the Hofer article describes Chin augmentation historically has uti- the technique in a cadaver and not a living lized a number of materials for enhancement, patient. He further notes that Hofer did not SROMS 2 VOLUME 21.2 The Art of Genioplasty Kevin L. Rieck, DDS, MD go on to perform these procedures in living The primary sensory innervation to the patients.13 chin area is from the paired mental nerves that exit the body of the mandible near the In the 1960s Converse and Wood-Smith apices of the premolar teeth. These nerves are as well as Hinds and Kent described the ver- the terminal extension of the inferior alveolar satility of the sliding genioplasty.5,14.15 As nerve from the third division of the trigeminal expected with a relatively new procedure nerve. The position of the mental nerves in longer, postoperative follow-up began to reference to the mental foramen and planned show some concerns that surgeons sought to osteotomies is well described by Hwang et improve. In the 1970s Gonzales-Ulloa, Loeb al.28 The authors looked at 30 fresh cadaveric and Field all described various methods to mandibles and 50 dry specimens document- address “witch’s chin” and deep submental ing the position of the mental nerve relative folds.16,17,18 The 1980s heralded the introduc- to the mental foramen and other aspects of tion of hydroxyapatite for use as an inlay or the mandible by dissection. onlay graft or to augment the lower facial height of the osteotomized chin.19,20 In the Information regarding the anatomic late 1990s through 2007, Zide and his col- position of the mental nerve is seen in Figure 1. leagues wrote a series of articles addressing The authors point out that, based on their numerous contemporary aspects of genio- study, a planned osteotomy of the chin must plasty evaluation, approaches, complications stay a minimum distance of 4.5mm below and refinements that serve as an excellent the mental foramen to avoid nerve injury and foundation for surgeons undertaking this advised a plain preoperative radiograph to procedure.21-27 Genioplasty today is used to document nerve position.28 Incidence of inju- address a variety of facial concerns from a ry and paresthesia of the mental nerves after balancing procedure in conjunction with or- sliding genioplasty has been reported to be as thognathic surgery to assisting with soft tis- high as 12%.29,30 sue contours and chin-neck enhancement for ___________________________________ patients undergoing elective facial surgery. Anatomy In addition to the historical aspects associated with procedures, I feel surgeons must have a sound knowledge of the relevant anatomy as well. Although, this article will not review the detail to which most should be familiar, it will discuss basic salient and Figure 1: Salient nerve anatomy as described by pertinent aspects associated with genioplasty Hwang et al. depicting the position of the mental procedures. nerve in relation to the mental foramen and inferior border of the mandible. A: 5 ±1.8 mm, B: 4.5 ± 1.9 mm, C: 9.2 ± 2.7 mm.28 SROMS 3 VOLUME 21.2 The Art of Genioplasty Kevin L. Rieck, DDS, MD The primary motor component to the 9 mm and 15 mm in thickness. Soft tissue muscles associated with the anterior aspect thickness varies between 8 mm and 11 mm of the chin are from the buccal and margin- and does not change appreciably after about al mandibular branches of the facial nerve. eight years of age.5 These muscles include the depressor labii inferioris, depressor anguli oris, mentalis and ANALYSIS OF THE CHIN orbicularis oris muscles.31 The lingual muscle pedicle of the genioplasty will include the Analysis of the chin will ultimately vary geniohyoid, mylohyoid and anterior digastric from surgeon to surgeon and be a function of muscles, which obtain their innervation from their training and experience. However, there the hypoglossal nerve (geniohyoid) and infe- are basic components that should be pres- rior alveolar nerves (mylohyoid and anterior ent in all evaluations. These include photo- digastric), respectively.31 graphic, radiographic, imaging analysis and Zide’s Quick Analysis of the Chin (QUAC).21 The primary muscle involved with the Photographic documentation of the preopera- genioplasty procedure itself is the mentalis tive state is an absolute medico-legal neces- muscle, which provides the primary vertical sity in contemporary surgical practice. (See support to the lower lip.5,31 Aspects associ- also Selected Readings in Oral and Maxillo- ated with this muscle will be detailed later in facial Surgery, Vol. 20, #3) Documenting the the article. The other muscles associated with patient’s appearance is needed to assist with the chin are usually not stripped completely the surgical plan, to critically evaluate post- nor disrupted to the same degree as the men- operative results, and to act as a reference talis muscle. of patient’s pre-existing features should that become necessary. A standard set of photo- Maintaining a broad pedicle to the chin graphs with a uniform background, set dis- is paramount to the blood supply of this os- tance to object, and set magnification, includ- teotomized segment.32 Improper reposition- ing different views at repose and smiling is ing of the mentalis muscle can result in un- ideal (Fig. 2, on p. 5) A short video of the sightly disfigurement of the chin known as patient in repose and with facial animation a “witch’s chin” deformity.17,33 The arterial can also be considered. supply to the muscles of the chin area is from the inferior labial arteries, which are termi- Radiographic analysis can include a nal extensions from the facial arteries.31 The number of possibilities. Plain films, such as bony chin is supplied from the inferior alveo- panoramic and lateral cephalometric images, lar artery. Venous drainage is via the inferior are extremely helpful as screening tools to labial, facial, maxillary and submental veins, rule out any type of osseous pathology and ultimately connecting with the facial or ante- provide a foundation for predicting antici- rior jugular veins.5 pated osseous and soft tissue changes in the sagittal plane. CT or cone-beam CT (CBCT) The osseous dimensions of the chin images are also helpful in this regard if avail- are greatest at the midline, varying between able, and the DICOM data sets can often be SROMS 4 VOLUME 21.2 The Art of Genioplasty Kevin L. Rieck, DDS, MD Figure 2: 18-year-old female seeking chin augmentation. Photos illustrate importance of different pre-surgical views. A: repose, B: smiling, C: patient’s “normal” posture with mentalis strain. Evaluation of all three views is important in making appropriate decisions regarding modification of the chin. ______________________________________________________________________________ incorporated into some type of imaging soft- tographs in addition to radiographic images ware for study and prediction analysis.(See to give some sense of anticipated change also Selected Readings in Oral and Maxillo- from the planned procedure.

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