ERN
INT ATI
IBUTION
TR
AL CON
ON
Facial Surgery
Modified Technique of Chin Augmentation With
MEDPOR for Asian Patients
Aesthetic Surgery Journal
32(7) 799­–803
© 2012 The American Society for
Aesthetic Plastic Surgery, Inc.
Reprints and permission:
http://www​.sagepub.com/
journalsPermissions.nav
DOI: 10.1177/1090820X12455191
www.aestheticsurgeryjournal.com
Jinde Lin, MD; and Xiaoping Chen, MD
Level of Evidence: 4
Keywords
chin augmentation, genial tubercle, mental protuberance, MEDPOR, facial surgery
High-density porous polyethylene (MEDPOR; Stryker, Inc,
Kalamazoo, Michigan) is a popular product for chin augmentation, which achieves good results.1-3 MEDPOR
implantation is less invasive than osteotomy. However,
modification of the external aspect of the implant may be
necessary, particularly for Asian patients, to create an
appropriate shape for the new chin. Because MEDPOR
implants are designed for Caucasian chin contours, the
inner aspect of the implant usually does not conform to
the mandible of the Asian patient, primarily due to the
genial tubercles and mental protuberance (Figure 1).
Moreover, it is difficult to contour the inner aspect of the
implant. Without appropriate modification, a gap may
exist between the implant and the chin. Discrepancies
between the mandible and inner aspect of the implant
may increase the incidence of implant displacement,
deformity and poor transition between the mandible and
the implant. Poor transition and implant displacement are
major reasons for implant removal. Some surgeons have
prevented these problems by contouring the distal part of
the implant.4
In the present report, we describe our modified technique for MEDPOR chin augmentation, which entails
Dr Lin is Associate Chief Physician in the Department of Surgery,
First Affiliated Hospital, School of Medicine, Zhejiang University,
Hangzhou, China. Dr Chen is Chief Physician, Department of Plastic
Surgery, Nanjing Friendship Plastic Surgery Hospital, Nanjing
Medical University, Nanjing, China.
Corresponding Author:
Dr Jinde Lin, Associate Chief Physician in the Department of
Surgery, First Affiliated Hospital, School of Medicine, Zhejiang
University, 79 Qingchun Road, Hangzhou, Zhejiang Province, China
E-mail: hzljd@sohu.com
Downloaded from http://asj.oxfordjournals.org/ by guest on March 4, 2016
Abstract
Background: Commonly used chin implants are made of silicone, expanded polytetrafluoroethylene (e-PTFE), or high-density porous polyethylene
(MEDPOR). Although MEDPOR is an effective implant for chin augmentation, modification of the external aspect of the implant is recommended,
particularly for Asian patients, to create an appropriate shape for the new chin. It is often difficult to contour the inner aspect of the implant to conform
to the patient’s mandible. Without modification, a gap may exist between the implant and mandible. To address this problem, a modified augmentation
technique was developed.
Objectives: The authors describe their modified technique for MEDPOR chin augmentation, which includes removal of the genial tubercles and, if
necessary, the mental protuberance.
Methods: Ninety-five patients underwent the modified MEDPOR technique of chin augmentation. Before placement of the contoured implant, a
drill was used to remove the patient’s genial tubercles. If the mental protuberance was deemed too prominent, it was removed as well. The implant was
inserted and fixed to the mandible with 2 titanium screws.
Results: Results were satisfactory in 90 cases. Chin shape was too “strong” in 4 patients, and another patient had poor transition between the implant
and mandible. Complications were minimal. The most common complication in this modified technique was lower lip numbness, which was transient
in all cases.
Conclusions: The MEDPOR chin implant can be effectively contoured to the mandible by removing the genial tubercle and/or mental protuberance.
This technique is less invasive than chin osteotomy. Successful results can be achieved with minimal risks.
800
Figure 1. Intraoperative view of genial tubercles and mental
protuberance.
Aesthetic Surgery Journal 32(7)
Figure 2. The right genial tubercle is intact; the left tubercle
has been removed.
Downloaded from http://asj.oxfordjournals.org/ by guest on March 4, 2016
removal of the patient’s genial tubercles and mental protuberance (when necessary).
Methods
From January 2005 through March 2009, chin augmentation with MEDPOR was performed in 95 Chinese
adults.
Physical Examination
Physical examination is the most important procedure in
preoperative assessment and planning. In this series, preoperative evaluation of the chin included symmetry, contour,
anterior/posterior projection, height, and occlusion.4 The
projection of the chin was assessed in the context of surrounding facial features, including projection of the nose,
relationship to the lips, and depth of the labiomental sulcus.
Two vertical lines were drawn, which extended downward
from the nasion and subnasale, while the patient’s head was
in the Frankfurt position. Normally, the anterior projection of
the mentum approaches approximately the vertical line from
the subnasale in men and is slightly anterior to the vertical
line from the nasion in women. A previous study documented that when the aesthetic plane is formed from the
nasal tip to the pogonion, both the upper and lower lips
should lie 1 to 2 mm posterior to the aesthetic plane.5 The
height of the lower face (from subnasale to mentum) should
equal that of the midface (from glabella to subnasale). The
height of the lower face is often subdivided into an upper
third (between the subnasale and lip contact [stomion]) and
lower two-thirds (between the stomion and mentum).4 The
ideal height of the lower face to the head and face were determined objectively. After careful evaluation of these regions in
our patients, the size and position of the implant were determined.
Figure 3. The implant is fixed to the mandible with 2
titanium screws. There is no gap between the implant and
the mandible.
Implant Selection and Contouring
The anthropometric measurements obtained from the physical examination were helpful for determining the correct
implant size. An implant with small projection was selected
for 20 patients (21.06%), medium projection for 66 patients
(69.47%), and large projection for 9 patients (9.47%). Before
insertion, the implant was contoured (including its height
Lin and Chen801
and width) in accordance with the dimensions determined
during each patient’s preoperative assessment.
Surgical Technique
The area to be dissected was marked with methylthioninium chloride. The operation was performed with the
patient under local or inhalational anesthesia. A mixture
of 1% lidocaine and 1:100 000 epinephrine was infiltrated
into the chin area. A transverse incision, approximately 4
cm long, was made 1 cm above the buccal sulcus, in the
midline. An appropriately sized subperiosteal pocket was
created in accordance with the marked area. The mandible’s anterior portion was fully exposed, including mental
neurovascular bundles, genial tubercles, and mental protuberance. Precautions were taken to avoid injury to the
mental neurovascular bundles. The genial tubercles and
mental protuberance (when indicated) were removed with
a drill (Figure 2). The bony material removed from the
chin did not exceed 2 mm in thickness.
The previously contoured implant was inserted into
the pocket. Two titanium screws (each 6-8 mm long)
were used to precisely and securely fix the implant to the
mandible (Figure 3). Careful examination was required
to ensure proper transition between the implant and
mandible.
The wound was irrigated and closed in 2 layers. A chin
dressing with mild compression was placed for 48 to 72
hours. Antibiotics were administered for 3 days.
Results
The study population comprised 69 women and 26 men (age
range, 18-42 years) of Asian descent. The follow-up period
ranged from 3 months to 51 months (average, 35 months).
All patients with microgenia had normal or near-normal
occlusion.
Postoperative photographic results were evaluated
by the surgeon and the patient at least 3 months after
the procedure. Good results were achieved in 90 patients
Downloaded from http://asj.oxfordjournals.org/ by guest on March 4, 2016
Figure 4. (A, C) This 21-year-old woman with microgenia and near-normal occlusion presented for correction of her
retrograde chin. (B, D) Six months after undergoing the modified MEDPOR technique of chin augmentation, which entailed
removal of the genial tubercles and mental protuberance.
802
Aesthetic Surgery Journal 32(7)
Downloaded from http://asj.oxfordjournals.org/ by guest on March 4, 2016
Figure 5. (A, C) This 42-year-old woman with microgenia and near-normal occlusion desired correction of her small
retrograde chin. (B, D) Twelve months after undergoing the modified MEDPOR technique of chin augmentation, which
entailed removal of the genial tubercles.
(95%). The chin shape was too “strong” in 4 patients,
and 1 patient had poor transition between the implant
and mandible. Among the 4 patients with a “strong”
chin, implants were removed in 2 cases and revised in
2 cases. The implant was refixed in the case with poor
transition.
Lin and Chen803
One patient whose result was good asked to have her
implant removed because her family disagreed with the
surgery.
Lower lip numbness, which occurred in 46 cases and
was the most common complication with this technique,
was transient and resolved within 3 to 6 months. There
was no incidence of infection.
Clinical results are shown in Figures 4 and 5.
Discussion
Conclusions
Chin augmentation with MEDPOR is less invasive than
osteotomy, and recovery is more rapid. In some patients,
particularly Asians, the implant will conform better to the
patient’s mandible if the genial tubercles or mental protuberance (when appropriate) are removed. Successful outcomes can be achieved, with minimal risk of complications.
Disclosures
The authors declared no potential conflicts of interest with
respect to the research, authorship, and publication of this
article.
Funding
The authors received no financial support for the research,
authorship, and publication of this article.
References
1. Sclafani QP, Thoma JR, Cox AJ, Cooper MH. Clinical and
historical response of subcutaneous expanded polytetrafluoroethylene (Gore-Tex) and porous high-density
polyethylene implants to acute and early infection. Arch
Otolaryngol Head Neck Surg. 1997;123:328-336
2.Yaremchuk MJ. Facial skeletal reconstruction using
porous polyethylene implants. Plast Reconstr Surg.
2003;111:1818-1827.
3. Cohen MS, Constantino PD, Friedman CD. Biology of
implants used in head and neck surgery. Facial Plast Surg
Clin North Am. 1999;7:17-33.
4. Gui L, Huang L, Zhang Z. Genioplasty and chin augmentation with MEDPOR implants: a report of 650 cases. Aesthetic Plast Surg. 2008;32(2):220-226.
5. Yaremchuk MJ. Facial skeletal augmentation with implants. In:
Thorne CHM, Beasley RW, Aston SJ, Bartlett SP, Gurtner
GC, Spear SL, eds. Grabb and Smith’s Plastic Surgery. 5th
ed. Philadelphia, PA: Lippincott; 2007:551-556.
Downloaded from http://asj.oxfordjournals.org/ by guest on March 4, 2016
MEDPOR is a popular implant in facial reconstruction
because of its high tensile strength and firm consistency
that resists material compression. The firm consistency of
the chin implant allows it to be easily fixed with screws
and to be contoured without fragmenting. The intramaterial porosity, which ranges from 125 to 250 µm, allows for
more extensive fibrous ingrowth.5 Soft-tissue ingrowth can
lessen the implant’s tendency to migrate, reduce capsule
formation in the surrounding fibrous tissue, and prevent
erosion of the underlying bone. Tissue ingrowth also helps
to prevent bacterial infection. In a large study by
Yaremchuk2 of facial skeletal augmentation with porous
polyethylene implants, there were no reports of bioincompatibility, and the complication rate was low.
The contour of the MEDPOR chin implant typically
requires modification for effective use in certain patients,
particularly Asians. Because the MEDPOR implant was
designed for Caucasian chin contours, its inner aspect usually is not a suitable match for the mandible of the Asian
patient. Moreover, it is difficult to contour the inner part of
the implant. However, the external aspect of the implant can
be carved to create a new chin of appropriate size and shape.
Although the implant material is somewhat flexible and can
be carved easily, a gap may still exist between its inner aspect
and the patient’s mandible because of the presence of genial
tubercles and excessive mental protuberance. The discrepancy in contour between the implant and the chin may result
in deformity of the implant, displacement of the distal part of
the implant, poor transition between the mandible and the
inner aspect of the implant, and/or compression of the mental neurovascular bundles. Therefore, we modified the mandible by removing the genial tubercles or mental protuberance
before inserting the implant. This allowed the implant to
better conform to the mandible, minimizing the likelihood of
these complications and reducing the risk of hematoma and
infection.
Although good outcomes can be achieved with MEDPOR
chin augmentation, other implants (eg, silicone, expanded
polytetrafluoroethylene [e-PTFE]) do not require removal
of genial tubercles or the mental protuberance. MEDPOR’s
firmness may necessitate removal of the mental protuberance and genial tubercles because, when the implant is
fixed with titanium screws, it is forced to conform to the
contour of the chin. Thus, the implant (particularly its
ends) would be displaced, resulting in poor transition
between the implant and chin. Silicone and e-PTFE
implants are much softer than MEDPOR and, after shaping,
both wings typically are very thin and soft. These characteristics, in conjunction with pressure from the overlying
soft tissue of the chin, allow these implants to conform
more readily to the patient’s original chin. Because the
amount of bony material removed from the patients’ chins
was minimal (approximately 1-2 mm thick), this alteration
did not impair the integrity of the mandible, nor did it
cause exposure of tooth roots.
Transient lower lip numbness is a relatively common
complication in patients who undergo this technique of
chin augmentation. To remove the genial tubercles and
mental protuberance, wide subperiosteal dissection is
required. Injury to the mental neurovascular bundles may
occur from the “pulling” force applied during surgery,
which may lead to paresthesia. However, this effect is usually transient. In our study, paresthesia resolved in all
patients by 6 months postoperatively.