Genioplasty 

Updated: Jan 11, 2016
Author: Edward W Chang, MD, DDS, FACS; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

Although patients who seek advice about facial cosmetic surgery often focus on structures such as the nose, the eyes, and the laxity of their skin, the facial plastic surgeon's assessment frequently identifies the lower third of the face as an area that could be surgically modified to improve overall facial appearance and harmony. The profile of a patient can be significantly altered with either a chin augmentation or reduction procedure. This, in turn, has a significant effect on overall facial symmetry.

Several surgical options exist for the treatment of chin deformities. Alloplastic chin implants and sliding genioplasty represent the 2 currently accepted methods of chin augmentation. However, to debate whether alloplastic augmentation or osseous genioplasty is the superior choice is beyond the scope of this article. Techniques for chin reduction include genioplasty and direct chin reduction. Skeletal surgery has been through the test of time, and still remains a valued procedure for the facial surgeon. Recent articles from variety of publications confirm the utility of the sliding genioplasty. Wolfe published a 28-year period series in 2006,[1] and Hoenig published a 10-year experience in 2007.[2]

History of the Procedure

Surgeons in the mid 1940s started using bony osteotomy techniques to address the retruded mentum. Currently, the sliding genioplasty is performed by physicians from several surgical subspecialties. For the protruding chin, options include a sliding genioplasty or an open reduction with a rotary burr.

Historically, various materials have been used to augment the chin, including paraffin, ivory, and methylmethacrylate, to name a few. Alloplastic implants such as silicone, polytetrafluoroethylene, and polyester mesh have gained a great deal of popularity through the years as a result of patient and surgeon satisfaction, as depicted in the image below. In the 1980s, Beekhuis and Johnson popularized Mersilene mesh (Ethicon, Somerville, NJ). A recent 14-year study showed Mersilene mesh to be safe and well tolerated for chin augmentation. Alloplasts, in general, are easy to place and are less time consuming than a sliding genioplasty, but their application is limited to the mild to moderately retruded chin.

An alloplastic chin implant. An alloplastic chin implant.

Autografts such as iliac crest and rib cartilage have been used more frequently for chin augmentation in the past. Nasal bone and cartilage have been used as well. Unfortunately, their use appears to be associated with an increased rate of infection, even after as many as 40 years.

Problem

When facial analysis identifies a patient's profile with facial dysharmony, determine whether an underlying occlusal and skeletal deformity or merely a poorly or overprojected mentum is present. When the poor projection is skeletal in nature, the situation is considered an Angle class II skeletal deformity. The Angle skeletal classification is based on the position of the first molar. 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 no skeletal malformation is present, the terms for a recessed chin include retrogenia, microgenia, retruded chin, hypoplastic mentum, and horizontal mandibular hypoplasia. The same holds true for the overprojected chin, eg, prognathia, protruded chin. In the literature, all these terms have been used interchangeably. In general, genioplasty implies an osseous movement, whereas mentoplasty suggests the use of an alloplastic implant. However, the two terms are currently used in a synonymous fashion.

Epidemiology

Frequency

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 must often be educated that this deficiency exists and that, with surgery, an overall balanced cosmetic result may be achieved.

Presentation

The preoperative consultation includes a complete history and physical examination, including dental history with occlusal evaluation along with standard facial photographs. In the analysis of the profile, the face is divided into thirds. Dividing the face from the hairline to the glabella, the midface from the glabella to the subnasale, and the lower third from subnasale to the menton is standard. Then the chin can be assessed to determine if it is in harmony with the remainder of the face.

In addition to the facial analysis, study dental occlusion and skeletal structures with the aid of preoperative photography as well as cephalometric and panoramic radiography. Functional and cosmetic goals should be discussed with the patient. When chin abnormalities are present, obtain additional studies. Perform a lateral soft tissue study, lateral cephalometric study, anteroposterior (AP) skull radiography, and occlusal panoramic radiography.

If skeletal or dental deformities are present, order dental models to be fashioned. Use this information to advise the patient on the choices available for obtaining the best result. If a skeletal abnormality exists, suggest orthodontic realignment and orthognathic surgery. When the patient desires a purely cosmetic correction, discuss options of alloplastic implant augmentation versus a sliding genioplasty. If the deformity is amenable to either of these treatment options, recommendations are based on the severity of the deformity and concomitant facial procedures being considered.

It is important to consider the mentolabial fold in planning for a chin augmentation. A large implant may worsen the depth and cause an imbalance in profile harmony. Several authors suggest considering methods to prevent a deep sulcus when performing a sliding genioplasty. Bertossi et al describe using fresh-frozen human bone allograft as an interpositional grafting material, which can also be used to efface the sulcus or fold.[3] Triaca et al describe a novel shield osteotomy to prevent the labiomental crease from deepening.[4] The buccal cortex is cut high, creating a shield effect and softening the crease.

Indications

Surgical goals include creating an aesthetically pleasing facial contour and establishing proportionate facial height. This may entail reduction of a prominent chin or augmentation of a poorly projected chin.

Ideally, the augmentation procedure should be performed with minimal morbidity. Generally, alloplastic implants are not technically demanding and have a low complication rate. Furthermore, these implants may be easily placed under local anesthesia. This is a well-accepted technique used in the correction of chins that have 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 3 dimensions of asymmetry, including vertical microgenia with and without retrogenia, vertical macrogenia with retrogenia, and prognathia. Alloplastic implant augmentation is excellent for minor abnormalities; however, surgical facility with osseous genioplasty permits treatment of more complex deformities. The proponents of the sliding genioplasty stress the fact that abnormalities in 3 dimensions can be addressed, making it a more versatile procedure. This technique has also been utilized when multiple problems with alloplastic chin implants was faced. The osseous genioplasty has been reported to provide the solution to difficulties encountered with the alloplastic techniques.[1]

Reduction can also be achieved via a direct approach. Through an intraoral labial approach or an external submental incision, the inferior cortex of the mandible may be burred down.

Relevant Anatomy

For an augmentation, the depth of the labiomental fold may dictate which technique is used. Alloplastic implants tend to deepen the sulcus, which may be particularly unattractive in female patients. With osseous genioplasty, the fold generally increases with advancements and/or vertical shortening and becomes more effaced with vertical lengthening.

The surgeon should always be cognizant of the location of the mental foramen. The mental foramen lies on the same vertical line defined by the pupil, infraorbital foramen and the second bicuspid tooth.

The mentalis muscle elevates and protrudes the chin. It attaches the chin to an area just beneath the tooth roots. An intraoral incision transects this muscle. Reestablishing this muscle is important; otherwise, chin ptosis may ensue.

Contraindications

When considering a mandibular 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 an aggressive bony reduction.

 

Workup

Imaging Studies

When chin abnormalities are present, obtain additional studies. Perform a lateral soft tissue study, lateral cephalometric study, anteroposterior (AP) skull radiography, and occlusal panoramic radiography.

Other Tests

See the list below:

  • Obtain standard facial photographs.

  • In addition to the facial analysis, study dental occlusion and skeletal structures with the aid of preoperative photography as well as cephalometric and panoramic radiography.

  • If skeletal or dental deformities are present, order dental models to be fashioned.

 

Treatment

Surgical Therapy

Alloplastic implants can be placed as an office procedure or in outpatient surgery. Common implant materials include Supramid, Mersiline, Gore-Tex, and silicone. Other options include autogenous or homologous (cadaveric) cartilage or bone, although these latter materials have a higher infection rate than is observed with autografts.

Preoperative Details

For patients undergoing sliding genioplasty, complete cephalometric tracings and measurements. Perform bony measurements and soft tissue analyses in the standard fashion. The cephalometric evaluation includes measurements of sella-nasion-subspinale A-point of the maxilla (S-N-A) and sella-nasion-supramentale B-point of the mandible (S-N-B) angles to provide information on the sagittal relationship between the anterior skull base and the maxilla and mandible, respectively.

Obtain soft tissue and lip-profile information by drawing a line perpendicular to the Frankfort horizontal plane (P-porion through O-orbitale) and through the subnasale point (sn). Measure the outline of the vermilion of the upper lip (vu), lower lip (vl), and the soft tissue pogonion (pg) in relationship to this line (reference range values: vu = 0 ± 2 mm, vl = -2 ± 2 mm, pg = -4 ± 2 mm), as depicted in the image below.

Preoperative cephalometric tracing is in the plann Preoperative cephalometric tracing is in the planning of a sliding genioplasty.

Determine the vertical height of the face by employing the method described by Powell and Humphreys.[5] The middle one third of the face, from nasale (n) to subnasale (sn), should be 43% of the vertical height of the total lower two thirds of the face; whereas the lower one third of the face, from sn to soft tissue menton (m), should be about 57% of the total lower two thirds of the face. Also, to have 0-3 mm of maxillary incisal show in repose is acceptable. Beyond this point, maxillary vertical excess is suspected.

Assess asymmetry in the transverse dimension by using standard photographs on frontal view along with the AP cephalometric radiograph. Asymmetry may exist for various reasons, and appreciating asymmetry preoperatively is crucial. Asymmetry can be easily corrected with an offset (transverse) genioplasty, but employ care to maintain the midline to prevent an iatrogenic asymmetry postoperatively.

Once deficiencies have been measured, plan the movement. The literature shows the ratio of correlation from bone to soft tissue movement is 1:0.6-1. More recent studies show the ratio to be about 1:0.9 for horizontal movements up to 8 mm. Beyond this length, muscular and soft tissue forces are thought to cause resorption. Also, literature reports less predictability in vertical movements. With alloplastic implants, on the other hand, preoperative measurements usually allow an accurate proper size to be implanted.

Local anesthesia is used to block the mental nerves and is also infiltrated locally as a field block.

Intraoperative Details

Alloplastic augmentation

For alloplastic augmentation, surgical approach options include a submental or an intraoral sulcus approach. A submental incision allows for other adjunctive procedures, such as cervical liposuction and effacement of platysmal banding, to be performed through it. On the other hand, an intraoral incision precludes a facial scar.

With either approach, carry the dissection down to the level of the periosteum. Take care to preserve and not traumatize the mental nerves. Mark the midline with a suture and place the lateral third of the implant subperiosteally, as depicted in the 1st two images below. Once the implant is in proper position, close the soft tissue in layers, paying special attention to the reattachment of the mentalis muscle to avoid a ptotic lower lip (ie, witch's chin deformity). Redrape the soft tissue with tape and schedule a follow-up visit with the patient within one week of surgery. The procedure should take around 15 minutes to complete, as depicted in the last two images below.

Placing implant through a submental incision. Placing implant through a submental incision.
Notice midline marking on implant. Notice midline marking on implant.
Submental incision closed. Submental incision closed.
Chin dressed. Chin dressed.

Sliding genioplasty

For patients undergoing sliding genioplasty, admit to the hospital only if orthognathic surgery is performed. Otherwise, the procedure can be performed in an outpatient setting even when concomitant procedures, such as rhinoplasty or liposuction, are performed. The sliding genioplasty can also be performed under local anesthesia or in an outpatient setting with good results; however, general anesthesia is most commonly used with this procedure. Patients are more comfortable, and the airway is better protected under general anesthesia. Unless a rhinoplasty is performed concurrently, nasotracheal intubation is preferred.

Like many surgeries in the head and neck, preservation of a named nerve along with strict attention to hemostasis is the key to a successful operation. In making the gingivolabial sulcus incision, leaving an adequate cuff of mucosa along with a good part of the mentalis muscle for later resuspension is crucial; this technique leads to avoidance of lower-lip ptosis, as depicted in the image below.

Access for an intraoral placement of an alloplasti Access for an intraoral placement of an alloplastic implant or for a sliding genioplasty.

Subperiosteal dissection is carried out laterally to identify the mental nerve, as depicted in the 1st image below. The foramina of the nerve are generally found between the first and second premolar teeth at the level of the origin of the mentalis muscle or 2-4 mm below the level of the bicuspid teeth apices. The foramina are situated deep to the midportion of the depressor anguli oris. Dissect inferolaterally to allow for a longer osteotomy, preventing unsightly mandibular notching. Leave the periosteum at the inferior rim intact. Align the skeletal midline with the overlying soft tissue corollary. Use a sagittal saw with a 30-degree bend to facilitate an even cut while minimizing soft tissue trauma, as depicted in the 2nd image below. Lateral cuts should be 4-5 mm below the foramina to compensate for the path of the inferior alveolar nerve.

Identification of the mental nerve. Identification of the mental nerve.
Bony cut with an oscillating saw. Bony cut with an oscillating saw.

Perform double osteotomies in the same manner. Plan asymmetric cuts well in advance. Fixation can be achieved with wires or plates. Wire fixation may lead to increased resorption because of greater periosteal dissection and a possible drop of the anterior segment from muscle pull. Great success has occurred using a single 4-hole titanium plate with 12-mm screws for males and 10-mm screws for females. Each plate is marked with the amount of movement obtained on the face of the plate, as depicted in the image below. Resorbable plates have also been used by oral and maxillofacial colleagues. Closure is accomplished in multiple layers. Resuspend the mentalis with 3-0 interrupted buried Vicryl sutures and close the mucosa with a running 3-0 chromic suture.

Advancement and plate placement. Advancement and plate placement.

Mentum reduction

This procedure can be performed in a similar manner to which a sliding genioplasty is performed, as described above. However, instead of advancement, the distal segment of bone is retruded and secured. Additionally, through either an intraoral or a submental incision, direct reduction of the prominent chin may be accomplished. Access should be wide enough to allow for an even reduction of the inferior border of the mandible, 1 cm lateral to the mental foramen, as depicted in the image below.

Prominent chins may be reduced with a burr. Prominent chins may be reduced with a burr.

Postoperative Details

Redrape the skin at the level of the labiomental fold with Mastisol (Ferndale Laboratories, Ferndale, MI) and Steri-Strip tape. Advise patients to stay on a soft diet and to rinse frequently with saline solution until the first postoperative visit. In the experience of the authors, the surgical time for the osseous genioplasty procedure ranges from 15-105 minutes, with an average surgical time of about 45 minutes. The alloplastic implantation is roughly 25% shorter in operative time. Chin reductions are equivalent in time to the genioplasties.

Follow-up

Schedule a follow-up visit with the patient on postoperative days 7 and 14.

Complications

Each of the procedures described has unique advantages, disadvantages, and complications.

Alloplastic mentoplasty may cause bone resorption, infection, extrusion, dehiscence, overprojection or underprojection, asymmetry, displacement, capsular contraction, lower-lip retraction, and chin ptosis. Studies show that resorption occurs to some extent in many, if not all, patients. One study showed up to 5 mm of resorption at 48 months after surgery. Resorption has been attributed to subperiosteal placement of the implant. Tension in the soft tissue pocket due to pressure from the overlying skin or mentalis musculature has been thought to cause this pressure resorption. The overall soft tissue profile, however, is not usually affected by this bone resorption. Reporting evidence to the contrary, a 1999 study on adult hounds by Pearson and Sherris showed no significant difference between supraperiosteal and subperiosteal placement of silastic implants.[6]

Osseous genioplasty has its own set of complications. Mental nerve injury, malunion, nonunion, irregularities, step-type deformities, lip drop, and overcorrection or undercorrection have been reported. Of note, undercorrection is better accepted than overcorrection in which the chin placed forward to the lower lip can yield a disharmonious profile. In a 10-year series, Hoenig reported that in the single sliding osteotomy group, no major branches of the mental nerves were transected. Paresthesia was only transient, usually lasting for only a few weeks. All who had only a single genioplasty recovered totally from a neurosensory deficit.[2]

Reduction genioplasty has a similar set of complications as those observed in advancement sliding genioplasties.

Strict attention to treatment planning and surgical technique can prevent most of these problems. Augmentation of the chin properly performed, either as a lone procedure or in conjunction with other procedures, yields an aesthetically pleasing result.

Outcome and Prognosis

Whether an alloplastic implant or an osseous implant is used, more than 90% of the patients are satisfied with their results. Complications observed with genioplasty are minimal, and benefits are readily evident to both patient and surgeon.

A study by Bedoucha et al indicated that in hyperdivergent adolescents who are exclusive or diurnal mouth breathers, genioplasty leading to spontaneous lip closure can help to recalibrate the upper airway.[7]

A study by Kumar et al indicated that the results of vertical reduction and advancement genioplasty are stable in the long-term, based on a review of presurgical and immediate postsurgical cephalograms, as well as cephalograms taken more than 2 years postsurgically.[8]

Future and Controversies

In addressing the underprojected chin, alloplastic implants and sliding genioplasty are generally considered equally acceptable. The benefits of the sliding genioplasty include its versatility in correcting chin abnormalities in every dimension and its relative ease of use. For chin reductions, a genioplasty or a direct reduction can result in a better profile. For the mild-to-moderate deficiency of the chin, alloplastic implantation is simple, easy to place, and requires only short operative time. Excellent results are obtainable, surgical time is acceptable, and patient satisfaction can be achieved with both alloplastic implants and sliding genioplasty. Additionally, the protruding chin can be addressed by either the genioplasty or by direct reduction.

The stability and predictability of skeletal surgery has been recently reconfirmed by Proffit and Turvey.[9] In addition, more advance mandibular skeletal surgeries have been introduced by Puricelli.[10]

The authors hope that these techniques are widely taught in residency training programs as methods to achieve a desired cosmetic result of the mentum area.