- Email: [email protected]
The Osseous Genioplasty
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CLINICS IN PLASTIC SURGERY Clin Plastic Surg 34 (2007) 485–500
The Osseous Genioplasty Judy L. Ward, -
MBBS,
Joe I. Garri,
The clinical evaluation The analysis Radiographic evaluation Determination of surgical procedure
In 1957, Richard Trauner and Hugo Obwegeser introduced the osseous genioplasty through an intraoral approach [1]. Despite its existence for nearly half a century and its versatility in solving a complex range of chin deformities, it remains a rusty tool in many surgeons’ armamentarium. Today, most surgical procedures performed on the chin are alloplastic implants; in many instances results are good, and complication are few when patients are selected appropriately. The osseous genioplasty is not solely within the domain of the maxillofacial or craniofacial surgeon; it is well within the reach of any surgeon whose practice involves facial aesthetics. The surgeon who masters this relatively simple procedure can solve a broad range of chin deformities that an implant cannot solve: a chin that is too long, too short, or asymmetric. The chin, occupying its very prominent position, is one of the elements of the complex facial structure that contribute to facial balance and harmony. The harmony of the facial profile is determined in part by the size, shape, position, and proportion of the chin with respect to the other facial elements [2,3]. The chin deformities can be described based on its volumetric mass and spatial position (Fig. 1). The chin can be small (microgenia), and it can
MD, DMD*,
-
S. Anthony Wolfe,
MD
Discussion with the patient Surgical technique The caveats References
be small in any number of planes: horizontal, vertical, or some combination. It may not necessarily be small but may be positioned posterior to its desired position (retrogenia). However, the retrogenia could be secondary (pseudoretrogenia) as a result of mandibular retrognathia (class II occlusion) or of vertical maxillary excess and clockwise rotation of the mandible. The chin can be large (macrogenia), and, as with microgenia, it can be large in any one of multiple planes: the horizontal, vertical, or some combination. The macrogenia could be caused by the underlying bone or by the volumetric excess of the soft tissue alone (pseudomacrogenia). Thus, because many patients seek aesthetic enhancement, the surgeon whose primary practice is focused on the soft tissue components should be aware of the need to assess the underlying dental skeletal anatomy. Frequently, patients presenting with complaints of a deficient chin indeed have mandibular deficiency with or without an anterior chin deficiency. In these patients, soft tissue and skeletal structure should be evaluated in a systematic way [3,4]. Patients should be counseled on the outcomes of formal orthodontic–orthognathic surgery versus genioplasty alone when there is malocclusion that is skeletally based. This article addresses only genioplasty.
Miami Children’s Hospital, 6280 Sunset Drive, # 400, Miami, Fl, 33143, USA * Corresponding author. E-mail address: [email protected] (J.I. Garri). 0094-1298/07/$ – see front matter ª 2007 Elsevier Inc. All rights reserved.
plasticsurgery.theclinics.com
doi:10.1016/j.cps.2007.05.009
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Ward et al
Fig. 1. (A) Ideal chin position for reference. (B) Microgenia. (C) Retrogenia. (D) Pseudoretrogenia (class II mandibular retrognathia, but a normal chin). (E) Macrogenia. (F) Pseudomacrogenia (caused by excess soft tissue chin pad, not by bone).
The clinical evaluation The facial proportions must be considered and evaluated as a whole with detailed analysis of the chin itself, its relative position, its relationship to the nose, the relative position and competence of the lips, the labiomental sulcus, and presence or absence of mentalis strain [4–6]. Additionally, the assessment should include the skeletal relationship of the maxilla to the mandible, and an intraoral examination should reveal any malocclusion that would indicate the need for a formal discussion of the need for orthognathic surgery. Although the issue frequently is overlooked, the intraoral examination also should assess the level of the
attached gingival of the anterior mandibular dentition because of the planned intraoral incision.
The analysis The morphologic assessment begins with a simple proportionate analysis by dividing the face along accepted anatomic landmarks—the trichion, glabella, subnasale, and menton—into upper, middle, and lower thirds (Fig. 2). When these divisions are in equal thirds, the face is said to be ‘‘ideal.’’ What is considered ‘‘ideal’’ has changed over time, however; many today agree that the attractive face has a proportionately greater lower third (Farkas)[7]. In addition the ‘‘ideal’’ must be referenced to the
The Osseous Genioplasty
Fig. 2. Proportionate analysis using facial thirds. (A) Acceptable facial proportions. (B) In microgenia, the lower third is vertically deficient. (C) In retrogenia, the vertical proportions may remain the same as illustrated.
particular race and culture and to the patient’s perception of the ‘‘ideal.’’ There are a number of quantitative analyses that the surgeon can use as a guide in assessing the position of the chin relative to the overall face, relative to the nose, and relative to the lips. Gonzalez-Ulloa and Stevens [3,8] reference the chin pogonion relative to the facial plane (the zero meridian) defined by the line perpendicular to the Frankfurt horizontal that intersects the nasion (Fig. 3). The chin
pogonion should be at or near this zero meridian. Without a set of protractors and rulers, the eye can discern the Gonzalez-Ulloa analysis. In contrast, the analyses presented by Ricketts, Steiner, and others are more complex and relate all three components: the chin to the lips to the nose [9,10]. The average, the ideal, and the most attractive position of the chin can vary tremendously based on any of these analyses. Perhaps the easiest rule of thumb is that the chin should be positioned
Fig. 3. Gonzalez-Uloa and Steven’s analysis: a line is dropped from the soft tissue nasion perpendicular to the Frankfort horizontal. This line is called the ‘‘zero meridian.’’ (A) The soft tissue pogonion of the chin should be at or just posterior to the zero meridian. (B) The chin is significantly posterior to the zero meridian.
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Fig. 4. A significant advancement of the pogonion is needed to establish more normal proportions. A chin implant of this thickness probably will lead to erosion of the symphysis. (Courtesy of P.K. Patel, MD, Chicago, IL.)
‘‘ideally’’ at the plane of the nasion (ie, the zero meridian) and not beyond the lower lip border with an adjustment for gender (more prominent in men and less prominent in women). To achieve the desired result, the surgeon ultimately must rely on his or her eye and understanding of the patient’s desired appearance. The final placement of the chin is based ultimately on the intraoperative clinical appearance and not solely on quantitative analysis.
Although in most circumstances clinical examination and photographic analysis alone suffice for the ‘‘ideal’’ positioning of the chin, radiographs can be of value. A formal cephalometric analysis from a lateral cephalogram can provide the quantitative confirmation of the chin position, the inclination of the osteotomy relative to the lower mandibular border, the mental foramen, and the
Fig. 5. The incision should be at least 5 to 6 mm inferior to the attached gingiva.
Fig. 6. The mandible is exposed below the mental foramen and lateral along the inferior mandibular border posteriorly toward molar region. The exposure in the subperiosteal plane should be kept to a minimum, leaving the soft tissue attached at the pogonion.
Radiographic evaluation
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Fig. 7. The horizontal osteotomy can be made with either an oscillating saw or, as depicted, with a reciprocating saw.
occlusal plane (Fig. 4). In cases of significant asymmetry, the frontal cephalogram can be of value. The orthopanorex can assist the surgeon in placing the osteotomy and fixation of hardware relative to the dental roots. Finally it will be readily apparent on the radiographic film when the patient’s problem is the soft tissue and not the bone. Any surgical procedure on the bone to correct the soft tissue problem will not result in a satisfying outcome for the surgeon or the patient.
Fig. 8. Course of the inferior alveolar nerve. Note that just before it exits the mental foramen, the nerve dips caudal. Ideally, the osteotomy should be approximately 6 mm below the mental foramen and extend well into the first molar region.
Fig. 9. The symphysis is advanced. Any resistance felt by the surgeon typically is caused by an incomplete osteotomy laterally at the inferior border.
Determination of surgical procedure The clinical examination primarily directs the surgical plan, which may involve changing the chin position in the vertical, horizontal, or lateral planes as guided by facial analysis and cephalometric measurements [2,11,12]. The desired quantitative movement of the soft tissue chin point can be determined preoperatively; based on this decision, the bony movement needed to produced a reciprocal soft tissue change is calculated. Depending on the vector of the movement, the corresponding soft tissue change will vary. With advancement genioplasty the ratio of soft tissue advancement to the bone has been predictably calculated to be 0.9:1. Additional benefits include increase in the submental length and cervicomental angle, improved relationship of the lower lip to the mandibular incisor with less eversion, and overall advancement of the genial–tongue–hyoid position which can have a functional effect in individuals who have nocturnal snoring [13]. The soft tissues of the chin follow vertical lengthening bony movement with a 1:1 ratio. Reduction osteotomies, however, have a less predictable effect on the soft tissues because of the redundancy of the soft tissue that is created. Horizontal reduction results in a soft tissue change which follows the ratio of 0.6:1, whereas for vertical reduction the ratio is 0.25:1 [13]. Although these ratios are useful, the assessment in the operating room as the chin is repositioned, and not the quantitative analysis, should determine the final soft tissue aesthetic appearance.
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Fig. 10. Once the symphysis is repositioned to the desired location, it is fixed either with (A, B, C) plates and screws or (D) with a lag screw technique. With the technique illustrated in A and B, the screw must engage the inferior cortex of the symphysis.
Discussion with the patient Patients should be educated about the appropriate indications for alloplastic or osseous genioplasty. The advantage of an alloplastic genioplasty is that it is a simple surgical procedure placed through a submental incision under local anesthesia with a choice of a wide variety of materials that are available off the shelf. Its disadvantages are that it effective only for a mild anterioposterior deficiency (generally less than 5 mm), removal may become necessary even many years later, erosion into the symphysis may occur into the dental roots aggravated with peri-implant bone resorption with aging, and it may become noticeable with animation. Although the osseous genioplasty is extremely versatile, has long-lasting results, and improves the neck contour through the reorientation of the cervical musculature, it requires general anesthesia and instrumentation and a longer
recovery and alters the sensibility of the lower lip for a period of weeks to months. Either procedure, when not well executed technically or with inappropriate planning, will lead to unfavorable results. The surgeon who can perform both can give a balanced discussion. Unfortunately, many who are uncomfortable with skeletal surgery frequently relate that the patient is unlikely to accept such a surgery.
Surgical technique The authors prefer to perform the genioplasty under general anesthesia, although sedation and local anesthesia can be used. Nasal intubation allows the surgeon to assess the chin position with the patient in occlusion and without the interference of the endotracheal tube. The patient is positioned supine, with the head in a neutral position and the neck fully exposed. Hyperextension of neck flexion will alter the surgeon’s intraoperative assessment of
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Fig. 11. The versatility of the osseous genioplasty. (A) Sliding genioplasty. (B) Two-tier genioplasty. (C) Jumping genioplasty. (D) Vertical lengthening. (E) Reduction genioplasty. (F) Centering genioplasty.
the chin position. The surgeon stands at the head of the table where contour and symmetry of the chin is best appreciated. Local anesthesia with a vasoconstrictor is infiltrated below the mucogingival sulcus, extending posteriorly to the second premolar. The incision then is performed with a needle-tip electrocautery or a surgical knife on the labial lip mucosa of the vestibule well above the attached gingival and sparing the frenulum (Fig. 5). Adequate exposure can be obtained by making the incision from cuspid to cuspid. The incision is deepened perpendicularly through the mentalis muscle. The periosteum is incised, and the anterior mandibular surface is exposed in the subperiosteal plane. The exposure is limited at the symphysis to maintain its vascular supply but is extended laterally toward the inferior border beneath the mental foramen (Fig. 6). Particular care is taken in exposing the inferior border until the mental foramen is identified clearly in the region of the second premolar and the mental nerve is protected [14]. Once the neurovascular bundle is visualized clearly, the exposure should continue posteriorly along the inferior border into the molar region. This extended osteotomy will allow repositioning as much of the inferior mandibular border as possible.
The midline of the mandible then is marked in reference to the dental midline and other facial structures, most commonly with the use of an oscillating saw to score a permanent vertical mark in the cortical bone. The oscillating saw then is used perpendicular to this line to make a full thickness osteotomy of the anterior mandible to the lingual cortex. The reciprocating saw then is used to complete the osteotomy laterally (Fig. 7). The level of the osteotomy must be at least 5 mm below the canine root [11] and, when extended laterally, 6 mm below the inferior to the mental foramen (Fig. 8) [15]. Angulation relative to the occlusal and mandibular planes should be taken into consideration when the osteotomy is made, because the inclination will alter the anterior mandibular height. When cutting the inferior border of the mandible laterally, the surgeon’s nondominant hand is used to palpate the tip of the blade, ensuring that both cortical walls have been cut fully. Frequently this is a site that is missed, and the posterior wall must be sectioned. When the osteotomies have been completed appropriately, the periosteal elevator is placed at the osteotomy site in the midline and, with a slight torquing motion (Fig. 9), the two segments of the bone are separated. Once the
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Fig. 12. Retrognathia with evidence of mentalis strain preoperative. An advancement genioplasty resulted in a much-improved facial profile and mentalis function. (A) Frontal preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral postoperative view. (Courtesy of P.K. Patel, MD, Chicago, IL.)
separation is completed, the distal segment should maintain its lingual attachments that consist of the two muscles, genioglossus and geniohyoid. These muscles must be stretched at this point, if advancement is planned. The distal segment then is placed in the desired position, and the inferior border is checked for any sharp edges or steps, which are smoothed with a rasp. Rigid fixation is achieved with plates or screws. Plates can be prefabricated to different lengths of chin advancement or adapted at the time in the operating room. For screw fixation alone, 2-mm bicortical screws are usually used; two screws are needed for adequate fixation (Fig. 10). When vertical shortening is anticipated, two osteotomies are performed, following a marking at the level of the B point of the mandible and
a second inferiorly, on a parallel plane. The distance between the parallel osteotomies should be calculated preoperatively and should be equal to the amount of desired reduction. The inferior osteotomy must be performed first so that the superior one is performed on a stable segment. After the osteotomies have been completed, the intervening bone fragment is removed, the two segments are placed in the proper position, and the fixation is applied. For an increase in the vertical dimension, a singular osteotomy is necessary, and an intervening bone graft is placed between the two bony segments. Once the fixation is completed successfully, the surgical site is irrigated copiously, and the soft tissues are closed. Closure can be done in two layers (the muscle layer followed by the mucosa) or in a single layer with a resorbable suture. An external
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Fig. 13. A 27-year-old man who desired a stronger chin underwent a 5-mm advancement genioplasty concomitant with submental liposuction. (A) Frontal, preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral postoperative view.
dressing is not necessary, but many surgeons advocate the use of foam tape around the chin to maintain soft tissue stability and reduce the postoperative edema. Patients generally are well recovered within a week of the surgery. The genioplasty procedure is differentiated further and classified by variations in technique, the reciprocal movements of the mandible segments, and the final result desired (Fig. 11) [1,11,12,16,17] 1. In the sliding genioplasty, the osteotomy segment slides anteriorly or posteriorly, and the vertical dimension of the lower third of the face is altered accordingly. (see Fig. 12,13). 2. In the jumping genioplasty, the caudal segment is moved anteriorly and placed in front of the
mandible, almost like an implant (Fig. 14). The lower soft tissue attachments of the segment should be preserved to avoid bone resorption. This nomenclature was used for the first time by Gilles [18] and indicates the attempt to improve the sagittal projection of the chin and decrease the height of the lower facial third. 3. In the graft genioplasty or interpositional genioplasty, the advancement is achieved by the interposition of bone graft between the mandible segments to advance the chin as well as increase the lower facial height (Fig. 15). 4. In the wedge genioplasty, a segment of bone is removed (Fig. 16). Two horizontal osteotomies parallel to each other and to the occlusal plane
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Fig. 14. (A) Preoperative view of patient with developmental retrogenia and retrognathia. (B) Postoperative view after premaxillary setback and jumping genioplasty. (C) Postoperative view following mandibular advancement and a second (sliding) genioplasty. (D) One year postoperatively, some relapse is evident. (E) Eight years postoperatively, there is further relapse. (F) Several years after a costal cartilage graft was placed through a submental approach. (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 2006;117:1435–46).
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Fig. 15. (A) Cleft lip patient with accompanying vertical microgenia. (B) Vertical lengthening with interpositional bone graft (C) Postoperative outcome.
Fig. 16. (A, B) Patient with vertical macroggenia. (C) Intraoperative parallel osteotomies for vertical reduction (D, E) Reduction genioplasty in the vertical plane only was undertaken. This patient also underwent a LeFort I, BSSO and Rhinoplasty.
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Fig. 17. the patient presented with a deficient, asymmetrical chin for which a centering advancement genioplasty was undertaken. (A) Frontal preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral, postoperative view.
are performed, and, after the caudal cut is made, the segment between the osteotomies is resected. This procedure reduces the height of the lower facial third considerably. It is important to let the patient know that a certain degree of soft tissue ptosis may occur and an adjunctive procedure may be required. 5. In the oblique genioplasty, the osteotomy is performed obliquely on the sagittal plane, allowing the distal fragment to slide anteriorly and superiorly if the posterior aspect of the cut is more caudal. When the posterior aspect of the cut is
more cephalad, the distal fragments slide anteriorly and inferiorly. 6. The stepladder/two-tiered genioplasty is used for important sagittal advancement without significant modification of the height of the lower facial third. Two osteotomies are performed, and the lower segment is advanced sagitally over an already advanced proximal segment. 7. In the ‘centering’ genioplasty, vertical and horizontal asymmetries can be corrected (Fig. 17). Depending on the asymmetry, a wedge of bone can be resected on the longer side and, if
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needed, mirror imaged to lengthen the contralateral deficient side.
The caveats There are a number of caveats that are useful to keep in mind when evaluating patients for chin deformities [19]
Fig. 18. Erosion of the symphysis by an alloplastic chin implant. An osseous genioplasty would have been more appropriate because of the thickness of the alloplastic implant needed. (Courtesy of P.K. Patel.)
1. An alloplastic chin implant is an appropriate surgical solution for the patient presenting with a mild sagittal deficiency, generally less than 5 mm. Beyond that thickness, symphyseal erosion over time becomes of concern (Fig. 18). The osseous genioplasty is technically more difficult to stabilize for small advancements because of the internal fixation but can be done if this is the surgeon’s practice. 2. The solution to failed alloplastic genioplasty is not another alloplastic genioplasty but an osseous genioplasty (Figs. 19 and 20). 3. The osseous genioplasty is the only surgical solution for vertical problems, asymmetry, and significant sagittal deficiency.
Fig. 19. (A, B) Previous chin implant which had lost projection over time. (C) Intraop Medpore implant in place with erosion of the cortex (D) Removal of the implant and advancement genioplasty (E, F) Postoperative result.
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Fig. 20. (A, B) Three previous chin implants, with visible puckering and skin irregularities. (C, D) Treated by implant removal scoring and release of the peri-implant capsule and scar tissue, and a lengthening genioplasty with interpositional cranial bone grafts (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 117: 1435–46, 2006).
4. An enlarged chin cannot be reduced by recontouring using a burr. Instead, a wedge of bone should be resected while leaving the contour alone. 5. Reduction genioplasty may require soft tissue redraping to improve the submental and cervical contour. 6. The osseous genioplasty cannot correct macrogenia caused by the soft tissue pad. It will lead to a disastrous result. 7. The symphysis should never be degloved of its vascular blood supply to minimize resorption. It must remain as a myo-osseous vascularized pedicle flap. The genioglossus and geniohyoid should be detached. 8. The osseous genioplasty is the only option for patients presenting with chin deformities in the context of a craniofacial condition (eg,
Treacher-Collins-Franceschetti syndrome, Nager syndrome, craniofacial microsomia, and Goldenhar syndrome, among others). Many patients will need significant advancements that may require readvancing genioplasty (staged), and many will require repositioning in all three planes to correct asymmetry (Fig. 21). Distraction genioplasty might be considered as another modality in these patients [20]. 9. An onlay graft of autogenous costal cartilage remains a useful adjunctive procedure when the osseous genioplasty cannot solve the chin deformity. The surgeon must rely on his or eye and understanding of the patient’s desired appearance to achieve the desired result. The final placement of the chin ultimately is based on the intraoperative
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Fig. 21. (A) Patient with Treacher-Collins-Franceschetti Syndrome:, premaxillary protrusion, mandibular retrognathia with severe retrogenia. (B, C) Illustrates the degree of advancement that is often required to correct this deformity. This frequently is corrected by staging the advancement as a jumping genioplasty followed by a sliding genioplasty or by distraction genioplasty. (D) Postoperative after premaxillary setback and jumping genioplasty. (E) Two years after mandibular advancement and a second genioplasty (sliding) (F) Five year later, the patient had a slight relapse of the mandibular advancement but a stable result with the chin. (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 117: 1435–46, 2006).
clinical appearance and not solely on presurgical quantitative analysis.
References [1] Trauner R, Obwegeser H. The surgical correction of mandibular prognathism and retrognathia with consideration of genioplasty: Part I. Surgical procedures to correct mandibular prognathism and reshaping of the chin. Oral Surg Oral Med Oral Pathol 1957 Jul 10(7):677–89. [2] McCarthy JG, Kawamoto HK Jr, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, editor. Plastic Surgery. Philadelphia: W.B. Saunders; 1990. p. 1188–200. [3] Gonzalez-Ulloa M. Quantitative principles in cosmetic surgery of the face (profileplasty). Plast Reconstr Surg 1962;29:186–98.
[4] Rakosi T. Cephalometric Radiology. Philadelphia: Lea & Febiger; 1982. p. 78–89. [5] Ferraro JW. Cephalometry and Cephalometric Analysis. In: Ferraro JW, editor. Fundamentals of Maxillofacial Surgery. New York: Springer; 1997. p. 234–6. [6] Vig K, Ellis E. Diagnosis and treatment planning for the surgical orthodontic patient. Clinics Plast Surg 1989;16:645–58. [7] Farkas LG, Sohm P, Kolar JC, Katic MJ. Munro IR Inclinations of the Facial Profile. Art Versus Reality Plast Reconstr Surg 1985;75:509–19. [8] Gonzalez-Ulloa M, Stevens E. The Role of Chin Correction in Profileplasty. Plastic & Reconstructive Surgery 1968;May 41(5):477–86. [9] Ricketts RM. Divine Proportion in Facial Aesthetics. Clinics in Plastic Surgery 1982;9:401–22. [10] Steiner CC. Cephalometrics For You & Me. Am J Orthod 1953;39;729, 755.
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[11] Kawamoto HK Jr. Osseous Genioplasty. Aesthetic Surgery Journal 2000;20(6):509–18. [12] Cohen SR. Genioplasty. In: Achauer BM, Eriksson E, Guyuron B, et al, editors. Plastic Surgery: Indications, Operations and Outcomes, vol. 5. Philadelphia: Mosby; 2000;2683–2703. [13] Roszkowski MJ. Soft Tissue Changes Associated With Orthognathic Surgery. Oral and Maxillofacial Surgery Knowledge Update 1995;. Vol 1, II:57–73. [14] Rajchel J, Ellis E, Fonseca RJ. The anatomical location of the mandibular canal: Its relationship to the sagittal ramus osteotomy. Int J Adult Orthod Orthognath Surg 1986;1(1): 37–47. [15] Ousterhout DK. Sliding Genioplasty, Avoiding Mental Nerve Injuries, Journal of Craniofacial Surgery 1996;July 7(4):297–8.
[16] McCarthy JG, Ruff GL, Zide BM. A surgical system for the correction of bony chin deformity. Clin Plast Surg 1991;18(1):139–52. [17] Guyuron B, Michelow B, Willis L. Practical Classification of Chin Deformities. Aesth Plast Surg 1995;19(25):7–264. [18] Gilles H, Millard DR Jr. The Principles and Art of Plastic Surgery. 1st Edition Boston: Little and Brown; 1957. Vol II, Chap 18. 361–2. [19] Wolfe SA, Rivas-Torres MT. The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 2006;117:1435–46. [20] Heller J, Gabbay JS, Kwan D, et al. Genioplasty Distraction Osteogenesis and Hyoid Advancement for Correction of Upper Airway Obstruction in Patients with Treacher Collins and Nager Syndromes. Plast Reconstr Surg 2006; 117(7):2389–98.
CLINICS IN PLASTIC SURGERY Clin Plastic Surg 34 (2007) 485–500
The Osseous Genioplasty Judy L. Ward, -
MBBS,
Joe I. Garri,
The clinical evaluation The analysis Radiographic evaluation Determination of surgical procedure
In 1957, Richard Trauner and Hugo Obwegeser introduced the osseous genioplasty through an intraoral approach [1]. Despite its existence for nearly half a century and its versatility in solving a complex range of chin deformities, it remains a rusty tool in many surgeons’ armamentarium. Today, most surgical procedures performed on the chin are alloplastic implants; in many instances results are good, and complication are few when patients are selected appropriately. The osseous genioplasty is not solely within the domain of the maxillofacial or craniofacial surgeon; it is well within the reach of any surgeon whose practice involves facial aesthetics. The surgeon who masters this relatively simple procedure can solve a broad range of chin deformities that an implant cannot solve: a chin that is too long, too short, or asymmetric. The chin, occupying its very prominent position, is one of the elements of the complex facial structure that contribute to facial balance and harmony. The harmony of the facial profile is determined in part by the size, shape, position, and proportion of the chin with respect to the other facial elements [2,3]. The chin deformities can be described based on its volumetric mass and spatial position (Fig. 1). The chin can be small (microgenia), and it can
MD, DMD*,
-
S. Anthony Wolfe,
MD
Discussion with the patient Surgical technique The caveats References
be small in any number of planes: horizontal, vertical, or some combination. It may not necessarily be small but may be positioned posterior to its desired position (retrogenia). However, the retrogenia could be secondary (pseudoretrogenia) as a result of mandibular retrognathia (class II occlusion) or of vertical maxillary excess and clockwise rotation of the mandible. The chin can be large (macrogenia), and, as with microgenia, it can be large in any one of multiple planes: the horizontal, vertical, or some combination. The macrogenia could be caused by the underlying bone or by the volumetric excess of the soft tissue alone (pseudomacrogenia). Thus, because many patients seek aesthetic enhancement, the surgeon whose primary practice is focused on the soft tissue components should be aware of the need to assess the underlying dental skeletal anatomy. Frequently, patients presenting with complaints of a deficient chin indeed have mandibular deficiency with or without an anterior chin deficiency. In these patients, soft tissue and skeletal structure should be evaluated in a systematic way [3,4]. Patients should be counseled on the outcomes of formal orthodontic–orthognathic surgery versus genioplasty alone when there is malocclusion that is skeletally based. This article addresses only genioplasty.
Miami Children’s Hospital, 6280 Sunset Drive, # 400, Miami, Fl, 33143, USA * Corresponding author. E-mail address: [email protected] (J.I. Garri). 0094-1298/07/$ – see front matter ª 2007 Elsevier Inc. All rights reserved.
plasticsurgery.theclinics.com
doi:10.1016/j.cps.2007.05.009
486
Ward et al
Fig. 1. (A) Ideal chin position for reference. (B) Microgenia. (C) Retrogenia. (D) Pseudoretrogenia (class II mandibular retrognathia, but a normal chin). (E) Macrogenia. (F) Pseudomacrogenia (caused by excess soft tissue chin pad, not by bone).
The clinical evaluation The facial proportions must be considered and evaluated as a whole with detailed analysis of the chin itself, its relative position, its relationship to the nose, the relative position and competence of the lips, the labiomental sulcus, and presence or absence of mentalis strain [4–6]. Additionally, the assessment should include the skeletal relationship of the maxilla to the mandible, and an intraoral examination should reveal any malocclusion that would indicate the need for a formal discussion of the need for orthognathic surgery. Although the issue frequently is overlooked, the intraoral examination also should assess the level of the
attached gingival of the anterior mandibular dentition because of the planned intraoral incision.
The analysis The morphologic assessment begins with a simple proportionate analysis by dividing the face along accepted anatomic landmarks—the trichion, glabella, subnasale, and menton—into upper, middle, and lower thirds (Fig. 2). When these divisions are in equal thirds, the face is said to be ‘‘ideal.’’ What is considered ‘‘ideal’’ has changed over time, however; many today agree that the attractive face has a proportionately greater lower third (Farkas)[7]. In addition the ‘‘ideal’’ must be referenced to the
The Osseous Genioplasty
Fig. 2. Proportionate analysis using facial thirds. (A) Acceptable facial proportions. (B) In microgenia, the lower third is vertically deficient. (C) In retrogenia, the vertical proportions may remain the same as illustrated.
particular race and culture and to the patient’s perception of the ‘‘ideal.’’ There are a number of quantitative analyses that the surgeon can use as a guide in assessing the position of the chin relative to the overall face, relative to the nose, and relative to the lips. Gonzalez-Ulloa and Stevens [3,8] reference the chin pogonion relative to the facial plane (the zero meridian) defined by the line perpendicular to the Frankfurt horizontal that intersects the nasion (Fig. 3). The chin
pogonion should be at or near this zero meridian. Without a set of protractors and rulers, the eye can discern the Gonzalez-Ulloa analysis. In contrast, the analyses presented by Ricketts, Steiner, and others are more complex and relate all three components: the chin to the lips to the nose [9,10]. The average, the ideal, and the most attractive position of the chin can vary tremendously based on any of these analyses. Perhaps the easiest rule of thumb is that the chin should be positioned
Fig. 3. Gonzalez-Uloa and Steven’s analysis: a line is dropped from the soft tissue nasion perpendicular to the Frankfort horizontal. This line is called the ‘‘zero meridian.’’ (A) The soft tissue pogonion of the chin should be at or just posterior to the zero meridian. (B) The chin is significantly posterior to the zero meridian.
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Fig. 4. A significant advancement of the pogonion is needed to establish more normal proportions. A chin implant of this thickness probably will lead to erosion of the symphysis. (Courtesy of P.K. Patel, MD, Chicago, IL.)
‘‘ideally’’ at the plane of the nasion (ie, the zero meridian) and not beyond the lower lip border with an adjustment for gender (more prominent in men and less prominent in women). To achieve the desired result, the surgeon ultimately must rely on his or her eye and understanding of the patient’s desired appearance. The final placement of the chin is based ultimately on the intraoperative clinical appearance and not solely on quantitative analysis.
Although in most circumstances clinical examination and photographic analysis alone suffice for the ‘‘ideal’’ positioning of the chin, radiographs can be of value. A formal cephalometric analysis from a lateral cephalogram can provide the quantitative confirmation of the chin position, the inclination of the osteotomy relative to the lower mandibular border, the mental foramen, and the
Fig. 5. The incision should be at least 5 to 6 mm inferior to the attached gingiva.
Fig. 6. The mandible is exposed below the mental foramen and lateral along the inferior mandibular border posteriorly toward molar region. The exposure in the subperiosteal plane should be kept to a minimum, leaving the soft tissue attached at the pogonion.
Radiographic evaluation
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Fig. 7. The horizontal osteotomy can be made with either an oscillating saw or, as depicted, with a reciprocating saw.
occlusal plane (Fig. 4). In cases of significant asymmetry, the frontal cephalogram can be of value. The orthopanorex can assist the surgeon in placing the osteotomy and fixation of hardware relative to the dental roots. Finally it will be readily apparent on the radiographic film when the patient’s problem is the soft tissue and not the bone. Any surgical procedure on the bone to correct the soft tissue problem will not result in a satisfying outcome for the surgeon or the patient.
Fig. 8. Course of the inferior alveolar nerve. Note that just before it exits the mental foramen, the nerve dips caudal. Ideally, the osteotomy should be approximately 6 mm below the mental foramen and extend well into the first molar region.
Fig. 9. The symphysis is advanced. Any resistance felt by the surgeon typically is caused by an incomplete osteotomy laterally at the inferior border.
Determination of surgical procedure The clinical examination primarily directs the surgical plan, which may involve changing the chin position in the vertical, horizontal, or lateral planes as guided by facial analysis and cephalometric measurements [2,11,12]. The desired quantitative movement of the soft tissue chin point can be determined preoperatively; based on this decision, the bony movement needed to produced a reciprocal soft tissue change is calculated. Depending on the vector of the movement, the corresponding soft tissue change will vary. With advancement genioplasty the ratio of soft tissue advancement to the bone has been predictably calculated to be 0.9:1. Additional benefits include increase in the submental length and cervicomental angle, improved relationship of the lower lip to the mandibular incisor with less eversion, and overall advancement of the genial–tongue–hyoid position which can have a functional effect in individuals who have nocturnal snoring [13]. The soft tissues of the chin follow vertical lengthening bony movement with a 1:1 ratio. Reduction osteotomies, however, have a less predictable effect on the soft tissues because of the redundancy of the soft tissue that is created. Horizontal reduction results in a soft tissue change which follows the ratio of 0.6:1, whereas for vertical reduction the ratio is 0.25:1 [13]. Although these ratios are useful, the assessment in the operating room as the chin is repositioned, and not the quantitative analysis, should determine the final soft tissue aesthetic appearance.
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Fig. 10. Once the symphysis is repositioned to the desired location, it is fixed either with (A, B, C) plates and screws or (D) with a lag screw technique. With the technique illustrated in A and B, the screw must engage the inferior cortex of the symphysis.
Discussion with the patient Patients should be educated about the appropriate indications for alloplastic or osseous genioplasty. The advantage of an alloplastic genioplasty is that it is a simple surgical procedure placed through a submental incision under local anesthesia with a choice of a wide variety of materials that are available off the shelf. Its disadvantages are that it effective only for a mild anterioposterior deficiency (generally less than 5 mm), removal may become necessary even many years later, erosion into the symphysis may occur into the dental roots aggravated with peri-implant bone resorption with aging, and it may become noticeable with animation. Although the osseous genioplasty is extremely versatile, has long-lasting results, and improves the neck contour through the reorientation of the cervical musculature, it requires general anesthesia and instrumentation and a longer
recovery and alters the sensibility of the lower lip for a period of weeks to months. Either procedure, when not well executed technically or with inappropriate planning, will lead to unfavorable results. The surgeon who can perform both can give a balanced discussion. Unfortunately, many who are uncomfortable with skeletal surgery frequently relate that the patient is unlikely to accept such a surgery.
Surgical technique The authors prefer to perform the genioplasty under general anesthesia, although sedation and local anesthesia can be used. Nasal intubation allows the surgeon to assess the chin position with the patient in occlusion and without the interference of the endotracheal tube. The patient is positioned supine, with the head in a neutral position and the neck fully exposed. Hyperextension of neck flexion will alter the surgeon’s intraoperative assessment of
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Fig. 11. The versatility of the osseous genioplasty. (A) Sliding genioplasty. (B) Two-tier genioplasty. (C) Jumping genioplasty. (D) Vertical lengthening. (E) Reduction genioplasty. (F) Centering genioplasty.
the chin position. The surgeon stands at the head of the table where contour and symmetry of the chin is best appreciated. Local anesthesia with a vasoconstrictor is infiltrated below the mucogingival sulcus, extending posteriorly to the second premolar. The incision then is performed with a needle-tip electrocautery or a surgical knife on the labial lip mucosa of the vestibule well above the attached gingival and sparing the frenulum (Fig. 5). Adequate exposure can be obtained by making the incision from cuspid to cuspid. The incision is deepened perpendicularly through the mentalis muscle. The periosteum is incised, and the anterior mandibular surface is exposed in the subperiosteal plane. The exposure is limited at the symphysis to maintain its vascular supply but is extended laterally toward the inferior border beneath the mental foramen (Fig. 6). Particular care is taken in exposing the inferior border until the mental foramen is identified clearly in the region of the second premolar and the mental nerve is protected [14]. Once the neurovascular bundle is visualized clearly, the exposure should continue posteriorly along the inferior border into the molar region. This extended osteotomy will allow repositioning as much of the inferior mandibular border as possible.
The midline of the mandible then is marked in reference to the dental midline and other facial structures, most commonly with the use of an oscillating saw to score a permanent vertical mark in the cortical bone. The oscillating saw then is used perpendicular to this line to make a full thickness osteotomy of the anterior mandible to the lingual cortex. The reciprocating saw then is used to complete the osteotomy laterally (Fig. 7). The level of the osteotomy must be at least 5 mm below the canine root [11] and, when extended laterally, 6 mm below the inferior to the mental foramen (Fig. 8) [15]. Angulation relative to the occlusal and mandibular planes should be taken into consideration when the osteotomy is made, because the inclination will alter the anterior mandibular height. When cutting the inferior border of the mandible laterally, the surgeon’s nondominant hand is used to palpate the tip of the blade, ensuring that both cortical walls have been cut fully. Frequently this is a site that is missed, and the posterior wall must be sectioned. When the osteotomies have been completed appropriately, the periosteal elevator is placed at the osteotomy site in the midline and, with a slight torquing motion (Fig. 9), the two segments of the bone are separated. Once the
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Fig. 12. Retrognathia with evidence of mentalis strain preoperative. An advancement genioplasty resulted in a much-improved facial profile and mentalis function. (A) Frontal preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral postoperative view. (Courtesy of P.K. Patel, MD, Chicago, IL.)
separation is completed, the distal segment should maintain its lingual attachments that consist of the two muscles, genioglossus and geniohyoid. These muscles must be stretched at this point, if advancement is planned. The distal segment then is placed in the desired position, and the inferior border is checked for any sharp edges or steps, which are smoothed with a rasp. Rigid fixation is achieved with plates or screws. Plates can be prefabricated to different lengths of chin advancement or adapted at the time in the operating room. For screw fixation alone, 2-mm bicortical screws are usually used; two screws are needed for adequate fixation (Fig. 10). When vertical shortening is anticipated, two osteotomies are performed, following a marking at the level of the B point of the mandible and
a second inferiorly, on a parallel plane. The distance between the parallel osteotomies should be calculated preoperatively and should be equal to the amount of desired reduction. The inferior osteotomy must be performed first so that the superior one is performed on a stable segment. After the osteotomies have been completed, the intervening bone fragment is removed, the two segments are placed in the proper position, and the fixation is applied. For an increase in the vertical dimension, a singular osteotomy is necessary, and an intervening bone graft is placed between the two bony segments. Once the fixation is completed successfully, the surgical site is irrigated copiously, and the soft tissues are closed. Closure can be done in two layers (the muscle layer followed by the mucosa) or in a single layer with a resorbable suture. An external
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Fig. 13. A 27-year-old man who desired a stronger chin underwent a 5-mm advancement genioplasty concomitant with submental liposuction. (A) Frontal, preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral postoperative view.
dressing is not necessary, but many surgeons advocate the use of foam tape around the chin to maintain soft tissue stability and reduce the postoperative edema. Patients generally are well recovered within a week of the surgery. The genioplasty procedure is differentiated further and classified by variations in technique, the reciprocal movements of the mandible segments, and the final result desired (Fig. 11) [1,11,12,16,17] 1. In the sliding genioplasty, the osteotomy segment slides anteriorly or posteriorly, and the vertical dimension of the lower third of the face is altered accordingly. (see Fig. 12,13). 2. In the jumping genioplasty, the caudal segment is moved anteriorly and placed in front of the
mandible, almost like an implant (Fig. 14). The lower soft tissue attachments of the segment should be preserved to avoid bone resorption. This nomenclature was used for the first time by Gilles [18] and indicates the attempt to improve the sagittal projection of the chin and decrease the height of the lower facial third. 3. In the graft genioplasty or interpositional genioplasty, the advancement is achieved by the interposition of bone graft between the mandible segments to advance the chin as well as increase the lower facial height (Fig. 15). 4. In the wedge genioplasty, a segment of bone is removed (Fig. 16). Two horizontal osteotomies parallel to each other and to the occlusal plane
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Fig. 14. (A) Preoperative view of patient with developmental retrogenia and retrognathia. (B) Postoperative view after premaxillary setback and jumping genioplasty. (C) Postoperative view following mandibular advancement and a second (sliding) genioplasty. (D) One year postoperatively, some relapse is evident. (E) Eight years postoperatively, there is further relapse. (F) Several years after a costal cartilage graft was placed through a submental approach. (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 2006;117:1435–46).
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Fig. 15. (A) Cleft lip patient with accompanying vertical microgenia. (B) Vertical lengthening with interpositional bone graft (C) Postoperative outcome.
Fig. 16. (A, B) Patient with vertical macroggenia. (C) Intraoperative parallel osteotomies for vertical reduction (D, E) Reduction genioplasty in the vertical plane only was undertaken. This patient also underwent a LeFort I, BSSO and Rhinoplasty.
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Fig. 17. the patient presented with a deficient, asymmetrical chin for which a centering advancement genioplasty was undertaken. (A) Frontal preoperative view. (B) Lateral preoperative view. (C) Frontal postoperative view. (D) Lateral, postoperative view.
are performed, and, after the caudal cut is made, the segment between the osteotomies is resected. This procedure reduces the height of the lower facial third considerably. It is important to let the patient know that a certain degree of soft tissue ptosis may occur and an adjunctive procedure may be required. 5. In the oblique genioplasty, the osteotomy is performed obliquely on the sagittal plane, allowing the distal fragment to slide anteriorly and superiorly if the posterior aspect of the cut is more caudal. When the posterior aspect of the cut is
more cephalad, the distal fragments slide anteriorly and inferiorly. 6. The stepladder/two-tiered genioplasty is used for important sagittal advancement without significant modification of the height of the lower facial third. Two osteotomies are performed, and the lower segment is advanced sagitally over an already advanced proximal segment. 7. In the ‘centering’ genioplasty, vertical and horizontal asymmetries can be corrected (Fig. 17). Depending on the asymmetry, a wedge of bone can be resected on the longer side and, if
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needed, mirror imaged to lengthen the contralateral deficient side.
The caveats There are a number of caveats that are useful to keep in mind when evaluating patients for chin deformities [19]
Fig. 18. Erosion of the symphysis by an alloplastic chin implant. An osseous genioplasty would have been more appropriate because of the thickness of the alloplastic implant needed. (Courtesy of P.K. Patel.)
1. An alloplastic chin implant is an appropriate surgical solution for the patient presenting with a mild sagittal deficiency, generally less than 5 mm. Beyond that thickness, symphyseal erosion over time becomes of concern (Fig. 18). The osseous genioplasty is technically more difficult to stabilize for small advancements because of the internal fixation but can be done if this is the surgeon’s practice. 2. The solution to failed alloplastic genioplasty is not another alloplastic genioplasty but an osseous genioplasty (Figs. 19 and 20). 3. The osseous genioplasty is the only surgical solution for vertical problems, asymmetry, and significant sagittal deficiency.
Fig. 19. (A, B) Previous chin implant which had lost projection over time. (C) Intraop Medpore implant in place with erosion of the cortex (D) Removal of the implant and advancement genioplasty (E, F) Postoperative result.
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Fig. 20. (A, B) Three previous chin implants, with visible puckering and skin irregularities. (C, D) Treated by implant removal scoring and release of the peri-implant capsule and scar tissue, and a lengthening genioplasty with interpositional cranial bone grafts (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 117: 1435–46, 2006).
4. An enlarged chin cannot be reduced by recontouring using a burr. Instead, a wedge of bone should be resected while leaving the contour alone. 5. Reduction genioplasty may require soft tissue redraping to improve the submental and cervical contour. 6. The osseous genioplasty cannot correct macrogenia caused by the soft tissue pad. It will lead to a disastrous result. 7. The symphysis should never be degloved of its vascular blood supply to minimize resorption. It must remain as a myo-osseous vascularized pedicle flap. The genioglossus and geniohyoid should be detached. 8. The osseous genioplasty is the only option for patients presenting with chin deformities in the context of a craniofacial condition (eg,
Treacher-Collins-Franceschetti syndrome, Nager syndrome, craniofacial microsomia, and Goldenhar syndrome, among others). Many patients will need significant advancements that may require readvancing genioplasty (staged), and many will require repositioning in all three planes to correct asymmetry (Fig. 21). Distraction genioplasty might be considered as another modality in these patients [20]. 9. An onlay graft of autogenous costal cartilage remains a useful adjunctive procedure when the osseous genioplasty cannot solve the chin deformity. The surgeon must rely on his or eye and understanding of the patient’s desired appearance to achieve the desired result. The final placement of the chin ultimately is based on the intraoperative
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Fig. 21. (A) Patient with Treacher-Collins-Franceschetti Syndrome:, premaxillary protrusion, mandibular retrognathia with severe retrogenia. (B, C) Illustrates the degree of advancement that is often required to correct this deformity. This frequently is corrected by staging the advancement as a jumping genioplasty followed by a sliding genioplasty or by distraction genioplasty. (D) Postoperative after premaxillary setback and jumping genioplasty. (E) Two years after mandibular advancement and a second genioplasty (sliding) (F) Five year later, the patient had a slight relapse of the mandibular advancement but a stable result with the chin. (From Wolfe et al, The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 117: 1435–46, 2006).
clinical appearance and not solely on presurgical quantitative analysis.
References [1] Trauner R, Obwegeser H. The surgical correction of mandibular prognathism and retrognathia with consideration of genioplasty: Part I. Surgical procedures to correct mandibular prognathism and reshaping of the chin. Oral Surg Oral Med Oral Pathol 1957 Jul 10(7):677–89. [2] McCarthy JG, Kawamoto HK Jr, Grayson BH, et al. Surgery of the jaws. In: McCarthy JG, editor. Plastic Surgery. Philadelphia: W.B. Saunders; 1990. p. 1188–200. [3] Gonzalez-Ulloa M. Quantitative principles in cosmetic surgery of the face (profileplasty). Plast Reconstr Surg 1962;29:186–98.
[4] Rakosi T. Cephalometric Radiology. Philadelphia: Lea & Febiger; 1982. p. 78–89. [5] Ferraro JW. Cephalometry and Cephalometric Analysis. In: Ferraro JW, editor. Fundamentals of Maxillofacial Surgery. New York: Springer; 1997. p. 234–6. [6] Vig K, Ellis E. Diagnosis and treatment planning for the surgical orthodontic patient. Clinics Plast Surg 1989;16:645–58. [7] Farkas LG, Sohm P, Kolar JC, Katic MJ. Munro IR Inclinations of the Facial Profile. Art Versus Reality Plast Reconstr Surg 1985;75:509–19. [8] Gonzalez-Ulloa M, Stevens E. The Role of Chin Correction in Profileplasty. Plastic & Reconstructive Surgery 1968;May 41(5):477–86. [9] Ricketts RM. Divine Proportion in Facial Aesthetics. Clinics in Plastic Surgery 1982;9:401–22. [10] Steiner CC. Cephalometrics For You & Me. Am J Orthod 1953;39;729, 755.
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[11] Kawamoto HK Jr. Osseous Genioplasty. Aesthetic Surgery Journal 2000;20(6):509–18. [12] Cohen SR. Genioplasty. In: Achauer BM, Eriksson E, Guyuron B, et al, editors. Plastic Surgery: Indications, Operations and Outcomes, vol. 5. Philadelphia: Mosby; 2000;2683–2703. [13] Roszkowski MJ. Soft Tissue Changes Associated With Orthognathic Surgery. Oral and Maxillofacial Surgery Knowledge Update 1995;. Vol 1, II:57–73. [14] Rajchel J, Ellis E, Fonseca RJ. The anatomical location of the mandibular canal: Its relationship to the sagittal ramus osteotomy. Int J Adult Orthod Orthognath Surg 1986;1(1): 37–47. [15] Ousterhout DK. Sliding Genioplasty, Avoiding Mental Nerve Injuries, Journal of Craniofacial Surgery 1996;July 7(4):297–8.
[16] McCarthy JG, Ruff GL, Zide BM. A surgical system for the correction of bony chin deformity. Clin Plast Surg 1991;18(1):139–52. [17] Guyuron B, Michelow B, Willis L. Practical Classification of Chin Deformities. Aesth Plast Surg 1995;19(25):7–264. [18] Gilles H, Millard DR Jr. The Principles and Art of Plastic Surgery. 1st Edition Boston: Little and Brown; 1957. Vol II, Chap 18. 361–2. [19] Wolfe SA, Rivas-Torres MT. The genioplasty and beyond: an end-game strategy for the multiply operated chin. Plast Reconstr Surg 2006;117:1435–46. [20] Heller J, Gabbay JS, Kwan D, et al. Genioplasty Distraction Osteogenesis and Hyoid Advancement for Correction of Upper Airway Obstruction in Patients with Treacher Collins and Nager Syndromes. Plast Reconstr Surg 2006; 117(7):2389–98.