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Sliding Genioplasty for Correction of Chin Abnormalities
Edward W. Chang, MD, DDS;
Samuel M. Lam, MD;
Matthew Karen, MD;
Jeffrey L. Donlevy, DDS, MD
Arch Facial Plast Surg. 2001;3:8-15.
ABSTRACT
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Background Correction of chin underprojection has a significant effect on facial
symmetry. Alloplastic chin implants and sliding genioplasty represent the
accepted methods of chin augmentation. While both procedures may be used for
retrognathia or microgenia, the sliding genioplasty may also be used in chin
asymmetry, prognathia, and vertical height discrepancies. We report our finding
from a 5-year review of our experience with sliding genioplasty.
Objectives To evaluate the results of sliding genioplasties performed by residents
and private practitioners, to illustrate the versatility and ease of this
procedure, and to confirm the excellent clinical results obtained with minimal
complications.
Design Retrospective case review.
Setting University center and private practice.
Patients Forty-three patients, aged 16 to 52 years (mean age, 21 years), underwent
sliding genioplasty alone (8 patients) or with concomitant orthognathic surgery
(35 patients).
Main Outcome Measures Patient satisfaction, physician satisfaction, chin movement, bone resorption,
and other complications.
Results Mean value of chin advancement was 8 mm in cases of isolated sliding
genioplasty and 4 mm when performed with orthognathic surgery. Average setback
for prognathic correction (6 patients) was 2 mm. Less than 0.5 mm of bone
resorption was encountered. Temporary unilateral mental nerve paresthesia
was noted in 1 patient. Thermal injury to the lower lip occurred in 1 patient.
Thirty-seven of 43 patients were extremely satisfied with their cosmetic result;
5 patients were very satisfied; and 1 patient was dissatisfied because of
the resultant occlusion. Physician satisfaction correlated closely with that
of the patients. Follow-up ranged from 6 months to 5 years, with an average
follow-up of 2.3 years.
Conclusions Our findings indicate excellent esthetic results with minimal complications.
Unlike alloplastic chin implants, sliding genioplasty allows correction of
many chin abnormalities, including underprojection, overprojection, chin asymmetries,
and/or vertical-height abnormalities. This underused technique is simple and
effective and should be included in the options of the facial plastic surgeon.
INTRODUCTION
GOALS IN augmentation of the mentum include the creation of an esthetically
pleasing contour and establishing proportionate facial height. Two principal
methods are available for chin augmentation—alloplastic implantation
and sliding genioplasty. Sliding genioplasty has often been neglected by the
facial plastic surgeon and been more favored by the oral maxillofacial surgeon.
It is beyond the scope of this article to debate whether alloplastic augmentation
or osseous genioplasty is the superior choice. Both methods have achieved
considerable success with correcting the underprojected mentum. Alloplastic
implants have been recognized as technically easy to perform with a low complication
rate. Advocates of sliding genioplasty stress that chin abnormalities in all
3 dimensions can be addressed, making it a more versatile procedure.1
Historically, Hofer2 is credited as the
first to describe the anterior horizontal osteotomy of the mandible in 1942.
Sir Harold Gillies3 treated a patient with
Treacher-Collins-Franchetti syndrome in 1947 with an open-approach genioplasty.
Since then, Converse and Wood-Smith4 have popularized
the procedure. Many surgical subspecialties have embraced the technique of
osseous genioplasty, making it the second most commonly performed osteotomy
of the facial bones.1
Several terms merit clarification at this point. Apart from a retruded
chin, retrognathia denotes occlusal misalignment due to Angle5
class II deformity, in which the mesiobuccal cusp of the maxillary first molar
is mesial (or anterior in the sagittal view to) the buccal groove of the mandibular
first molar (Figure 1), or the maxillary
canine is anterior to the embrasure formed by the mandibular first bicuspid
and canine. When hypoplasia of the mandible exists, then the term "micrognathia"
has been used. If no malocclusion is present, then the retruded chin has been
referred to as "microgenia," "retrogenia," or "hypoplastic mentum." Further,
mentoplasty generally implies the use of an alloplastic implant, whereas genioplasty
should be reserved for osseous movement of the mentum.
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Figure 1. Angle's skeletal classification
is based on the first molar teeth relationship in the sagittal plane. The
mesial buccal (MBC) cusp of the maxillary first molar lies in the buccal groove
(BG) of the mandibular first molar in class I occlusion. In class II occlusion
the MBC is anterior to the BG. In class III the MBC is posterior to the BG.
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Chin augmentation is a satisfying procedure for patient and surgeon
alike. Guyuron and Raszewski6 reported a patient
satisfaction rate of 85% to 90% for alloplastic mentoplasty and 90% to 95%
for osseous genioplasty. However, each method of chin augmentation has its
own unique disadvantages and complications. Morbidity associated with alloplastic
mentoplasty include bone resorption, infection, extrusion, dehiscence, inappropriately
sized implant, asymmetry, displacement, capsular contraction, lower lip retraction,
and chin ptosis.7-8 Bone resorption
has been blamed on many factors, from subperiosteal insertion to tension caused
by the overlying skin, subcutaneous tissue, or musculature. Pearson and Sherris,9 however, showed no significant difference between
supraperiosteal and subperiosteal placement of the Silastic implants in a
study on adult hounds. Even though clinically bone resorption due to implant
placement is not a significant problem, Robinson and Shuken10
do show at least some degree of bone loss in many of their patients. Further,
some investigators argue that severe chin retrusion corrected with a large
alloplastic implant may produce an unnaturally deep labiomental sulcus. Osseous
genioplasty has its own associated complications: mental nerve injury, malunion,
nonunion, irregularities, step-type deformities, asymmetry, lip drop, overcorrection,
and undercorrection. Undercorrection is better accepted than overcorrection
of the chin. If the chin is placed beyond the plane of the lower lip, a disharmonious
profile results. Done properly, the augmentation of the chin performed as
a lone procedure or done in conjunction with other procedures yields an esthetically
pleasing result.
Of historical interest, autograft augmentation with nasal bone or cartilage
was popularized by Aufricht in the late 1950s.11
Unfortunately, this technique has been associated with an increase in infections.
Kelly et al12 described a patient who developed
an infection 40 years after her autograft procedure.
Common alloplastic implant materials include Silastic (solid silicone;
Michigan Medical Corporation, Santa Barbara, Calif), Gore-Tex (W. L. Gore
& Associates, Flagstaff, Ariz), and Mersilene mesh (Ethicon, Somerville,
NJ). Gross et al13 reported a 14-year experience
with the use of Mersilene mesh. It was found to be safe and well tolerated.
The only disadvantage in using Mersilene mesh was the time needed to fold
and shape the mesh.13
We have found the sliding genioplasty to have similar success. A significant
advantage of the sliding genioplasty is the ability to correct chin deformities
in 3 dimensions: coronal asymmetry (Figure
2), vertical microgenia with or without retrogenia, and vertical
macrogenia with retrogenia and prognathia.14
We contend that facility with genioplasty allows treatment of more complex
deformities. We describe the findings of our 5-year experience with sliding
genioplasty performed by residents in a teaching hospital and by a single
private practitioner. This article will demonstrate the ease and versatility
of this procedure and illustrate the excellent esthetic outcomes.
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Figure 2. Asymmetry of the chin can be addressed
by a sliding genioplasty as shown.
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PATIENTS AND METHODS
PATIENTS
Forty-three (29 female and 14 male) consecutive patients who underwent
a sliding genioplasty from 1995 to 1999 were retrospectively reviewed. They
were aged 16 to 52 years, with a mean age of 21 years. Most (35 patients)
underwent a combined genioplasty with orthognathic surgery (Figure 3A-B), whereas 8 patients underwent genioplasty alone (Figure 4A-D). In 2 patients alloplastic implants
were removed prior to orthognathic surgery. Thirty-two patients had advancement
genioplasty with orthognathic surgery (Figure
3). Setback genioplasty was performed on 6 patients, 3 of whom also
had orthognathic surgery. Of the remaining 5 patients who had genioplasty
alone, 4 underwent advancement and 1 had correction of asymmetry (Figure 5).
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Figure 3. Preoperative (A) and postoperative
(B) lateral views of a patient who underwent orthognathic surgery and chin
advancement.
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Figure 4. Preoperative (A and B) and postoperative
(C and D) frontal lateral views of a patient who underwent rhinoplasty, cervical
liposuction, and chin advancement.
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Figure 5. Peroperative (A) and postoperative
(B) lateral views of a patient who underwent a correction for an asymmetric
chin.
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Surgical procedures were performed in a university setting and in a
private practice. All procedures were performed as ambulatory, unless concomitant
orthognathic surgery required maxillomandibular fixation and a hospital stay.
The maximum hospital stay was 2 days. Patients' medical records noted the
surgical goals, level of satisfaction for the patient and the surgeon, amount
of osseous movement, operative time, evidence of bone resorption on follow-up
cephalogram, and other complications. Follow-up was 6 months to 5 years, with
an average of 2.3 years.
METHODS
Initial consultation included a complete medical history and physical
exmination, including a dental history with occlusal evaluation along with
standard facial photographs, lateral cephalogram, anteroposterior skull x-ray
film series, and dental panoramic tomogram (Orthopantomograph; Siemens Corp,
Iselin, NJ). Functional and cosmetic goals were determined. In addition, if
skeletal or dental deformities were present, dental models were sculpted.
This information was used to advise the patient about the available surgical
options. If a skeletal abnormality existed, orthodontic realignment with orthognathic
surgery was suggested. When the patient desired only cosmetic correction and
his or her deformity could be addressed by either treatment modality, options
for both alloplastic implant and sliding genioplasty were discussed. Recommendation
was based on the severity of the deformity and concomitant facial procedures
being considered. Criteria described by Sykes and Frodel15
were used in the decision-making process. They recommended treatment of mild
to moderate abnormalities with either alloplastic implantation or osseous
genioplasty, whereas in severe abnormalities only sliding genioplasty was
recommended.
If sliding genioplasty was considered, cephalometric tracings and measurements
were completed. Cephalometric points SNA and SNB (S indicates sella; N, nasion; A, subspinale; and B,
supramentale) were plotted to assess the sagittal relationship between the
anterior skull base and the maxilla and mandible, respectively (Figure 6). 16 Soft tissue measurements
were assessed by pogonial position vis-à-vis a vertical line traced
through the subnasale and perpendicular to the Frankfort plane. The outline
of the vermilion of the upper lip, vermilion of the lower lip, and the soft
tissue pogonion was measured in relationship to this line. Normal values for
these measurement areas follow: vermilion of the upper lip, 0 mm (±2
mm from reference); vermilion of the lower lip, -2 mm (±2 mm
from reference); and soft tissue pogonion, -4 mm (±2 mm from
reference) (Figure 7). 17
Ideal vertical facial-height dimensions were obtained according to the Powell
and Humphreys'18 method, namely, the lower
third of the face (subnasale to menton) should approximate 57% of the lower
two thirds of the face, and the middle third of the face (nasale to subnasale)
should make up 43% of the lower two thirds of the face. In repose it is acceptable
to have 0 to 3 mm of maxillary incisal show. Incisal show beyond this indicates
maxillary vertical excess. Anteroposterior x-ray films were helpful to assess
chin asymmetry in the transverse dimension.
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Figure 6. Bony landmarks are traced and
identified. S indicates stella; N, nasion; P, porion; O, porion; A, point
of the maxilla; B, point of the mandible; Me, bony mentum; and Go, gonion.
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Figure 7. Soft tissue profile is traced
off the lateral cephalometric radiograph. Points of interest include: TR,
trichion; N, soft tissue nasion; SN, subnasale; O, porion; P, porion; VU,
vermillion of the upper lip; VL, vermillion of the lower lip; and PG, soft
tissue pogonion.
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Once deficiencies are measured, the amount and direction of movement
can be planned. Up to 8 mm of bony advancement, a 1:1 ratio of soft tissue
to bony translation exists. Osseous advancement of the chin beyond 8 mm requires
freeing the muscular attachments for maximal movement of the bony segment.
However, the ratio of soft tissue to bony movement decreases to approximately
1:0.6 despite freeing the musculature because of excessive resorptive forces
by the presumed overlying tissues. Less predictable ratios are reported for
vertical movements.19-20 Special
consideration was paid to the labiomental fold because it has an appreciable
effect on the final cosmetic result. The depth of the fold will generally
increase with advancements and/or vertical shortening and decrease with vertical
lengthening.1
Although sliding genioplasty under local anesthesia21
has been reported with good results, all patients in our series underwent
general anesthesia according to the surgeon's preference. Unless a concomitant
rhinoplasty was performed, nasoendotracheal intubation was favored. The procedure
has been well described by Sykes and Frodel.22
Some of the salient points of the surgery will be included herein.
In making the gingivobuccal incision, it is crucial to leave an adequate
cuff of mucosa for ease of closure and mentalis muscle to avoid lower lip
and chin ptosis. Subperiosteal dissection is carried out laterally to identify
the mental nerve, which is generally located between the first and second
premolars at the level of the origin of the mentalis muscle or 2 to 4 mm below
the level of the bicuspid teeth. It is deep to the midportion of the depressor
anguli oris.23 Dissection is then taken inferolaterally
to permit a longer osteotomy and thereby prevent unsightly mandibular notching.
Periosteum at the inferior margin of the mandible should be left intact to
assure a broad pedicle for vascular integrity. Skeletal midline should be
carefully preserved by inscribing a reference line in the midline to prevent
postoperative iatrogenic asymmetries.
Although straight saws have been used with success, we find a sagittal
saw with a 30° bend allows for an even cut while minimizing soft tissue
trauma (Figure 8 and Figure 9) Lateral cuts should be 4 to 5 mm below the mental nerve
foramina to compensate for the path of the inferior alveolar nerve. Fixation
can be achieved with wires or plates. When wire fixation is used, there is
the potential for increased bone resorption due to greater periosteal dissection
as well as possible drop of the bony segment due to muscle pull.20
We use a single 4-hole titanium plate (Stryker-Leibinger, Dallas, Tex)(Figure 10) with 12-mm screws for males and
10-mm screws for females. A larger screw is used if the posterior cortex of
the mandible is not engaged at these lengths.
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Figure 8. Diagrammatic representation of
the access needed for the sliding genioplasty. Mental nerve identification
is facilitated by following the origin of the mentalis muscle to a point between
the lower first and second premolar teeth.
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Figure 9. A, Operative photographs demonstrate
the midline marking needed to prevent iatrogenic asymmetry. B, Plate in place.
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Figure 10. A prebent 4-hole titanium plate
with millimeter markings gives rigid fixation keeping the distal segment in
place.
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Closure is accomplished in layers. The mentalis muscle is resuspended
with 3-0 interrupted, buried polyglactin (Vicryl; Ethicon, Somerville, NJ)
sutures. Mucosa is then reapproximated with a running 3-0 chromic suture.
The skin is redraped at the level of the labiomental fold with skin adhesive
such as Mastisol (Ferndale Laboratories, Ferndale, Mich) and sterile tape
(Steri-Strip; 3M, St Paul, Minn). Patients were advised to maintain a soft
diet and to rinse their mouths frequently with a saline solution until the
first postoperative visit at 1 week.
RESULTS
The main outcome measures of our study were patient satisfaction, physician
satisfaction, chin movement, bone resorption, and other complications. We
also evaluated operative time, which ranged from 15 minutes to 1 hour 45 minutes.
The average time was 45 minutes. The broad range of time was because of the
inclusion of cases that the residents performed.
Patient satisfaction was determined by a written questionnaire completed
at the 6-month follow-up appointment. The survey ranked satisfaction on a
4-point scale with 1 indicating dissatisfied; 2, satisfied; 3, very satisfied;
and 4, extremely satisfied. Thirty-seven (86%) of the 43 patients were extremely
satisfied with their results; 5 (11.6%) of the 43 patients were very satisfied.
One patient was unhappy with his dental occlusion and deemed his outcome unsatisfactory.
The surgeons felt extremely satisfied in 39 (90.6%) of the 43 cases and very
satisfied in 4 (9.4%) of the 43 cases. Through postoperative photographic
analysis, the operating surgeon ranked his results (using the same 4-point
scale).
Mean value of chin advancement was 8 mm in cases of isolated sliding
genioplasty and 4 mm when performed with orthognathic surgery. Average setback
for prognathic correction (6 cases) was 2 mm. When orthognathic surgery is
done, there is movement of the mandible, thus requiring less movement of the
chin. There were more combination cases done rather than sole genioplasties
(Table 1).
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Table 1. Procedures and Average Movement
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One-year cephalograms were performed if the patient or surgeon noted
any clinical evidence of bone resorption or movement (Figure 11). No greater than 0.5 mm of resorption was noted in any
case. No major complications from sliding genioplasty were encountered. Three
(6.9%) short-term complications were seen. One patient had unilateral mental
nerve paresthesia, which resolved in 1 month with no residual deficit. A poorly
guarded cautery tip caused a lower lip burn that healed within 1 week. A patient
with orthodontic braces had poor healing of the intraoral incision but opted
not to have it addressed. We believed that the braces may have prevented proper
oral hygiene. No revision surgical procedures were necessary. There were no
cases of infection, excessive hemorrhage, nonunion, malunion, bone necrosis,
iatrogenic asymmetry, movement of the distal segment, or a need for plate
removal (Table 2).
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Figure 11. Preoperative (A) and postoperative
(B) lateral cephalometric radiographic views. Preoperative (C) and postoperative
(D) panoramic views (Orthopantomography; Siemens Corp, Iselin, NJ) of the
same patient.
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COMMENT
It is well established that chin position and proportion have a significant
influence on facial profile and harmony. In evaluating the profile of patients
who seek cosmetic enhancement of the face, the published norms of facial ratios
and radiographic cephalometric measurements serve as valuable guides in determining
midface and lower face proportions. Poor chin projection is frequently unappreciated
by patients seeking reduction rhinoplasty. It is the responsibility of the
consulting surgeon to call attention to the profile deficits of the lower
third of the face and to recommend treatment when appropriate.
In addressing the underprojected chin, alloplastic mentoplasty and sliding
genioplasty both represent viable surgical options. Our experience with sliding
genioplasty confirms previous reports of excellent cosmetic results with minimal
risk of adverse effects. Our results indicate excellent outcomes attainable
at all levels of training. The diverse nature of clinical settings (private
practice vs resident training program) in our study attests to the safety
and ease of performance of this procedure.
As mentioned, sliding genioplasty offers the distinct advantage of addressing
a host of chin abnormalities, from underprojection, overprojection, vertical-height
disparities to transverse asymmetries. Riley and Powell24
have reported on orthognathic surgery and related osteotomies for obstructive
sleep apnea. Studies are investigating the benefits of sliding genioplasty
in the patient with retrognathia and obstructive sleep apnea syndrome.
Distraction osteogenesis is being met with favorable results from oral
maxillofacial surgeons and plastic surgeons; yet osseous techniques are not
widely taught in otolaryngology–facial plastic training programs. It
is our hope that this article will refocus attention to the sliding genioplasty
so more residents will acquire the clinical experience needed to use this
technique when the appropriate patient should present with the need.
CONCLUSIONS
Sliding genioplasty offers a viable alternative to alloplastic mentoplasty
to correct chin retrusion. Our results demonstrate a very high patient satisfaction
(42 patients, 98%) and good cosmetic result with low morbidity. Unlike alloplastic
mentoplasty, sliding genioplasty allows for correction of many chin abnormalities.
We recommend that this technique be more widely included in otolaryngology–facial
plastic training programs and in the options afforded the facial plastic surgeon.
AUTHOR INFORMATION
Accepted for publication October 18, 2000.
Presented in part at the American Academy of Facial Plastic and Reconstructive
Surgery section of Combined Otolaryngology–Head and Neck Surgery Scientific
Meeting, Orlando, Fla, May 13, 2000.
Dr Chang is a Facial Plastic Surgery Fellow at the University of South
Florida, Tampa. Dr Karen is a Facial Plastic Surgery Fellow at LSU–Health
Science Center, Shreveport, La.
Corresponding author: Edward W. Chang, MD, DDS, Facial Plastic Surgery
Fellow, 800 S Dakota Ave, Apt 415, Tampa, FL 33606 (e-mail: ed614{at}msn.com).
From the Departments of Otolaryngology–Head and Neck Surgery,
University of South Florida, Tampa (Dr Chang); Columbia University, New York,
NY (Dr Lam), LSU–Health Science Center, Shreveport, La (Dr Karen). Dr
Donlevy is in private practice in Redondo Beach, Calif. The authors have no
commercial, proprietary, or financial interest in the products or companies
described in this article.
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