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TITLE:   CHIN  AND MALAR IMPLANTS
SOURCE:  Dept. of Otolaryngology, UTMB, Grand Rounds
DATE:    September 6, 1995
RESIDENT PHYSICIAN:     Michael Bryan, M.D.
FACULTY:                Karen Calhoun, M.D.
DATABASE ADMINISTRATOR: Melinda McCracken, M.S.
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"This material was prepared by resident physicians in partial fulfillment 
of educational requirements established for the Postgraduate Training 
Program of the UTMB Department of Otolaryngology/Head and Neck Surgery 
and was not intended for clinical use in its present form.  It was 
prepared for the purpose of stimulating group discussion in a conference 
setting.  No warranties, either express or implied, are made with respect 
to its accuracy, completeness, or timeliness.  The material does not 
necessarily reflect the current or past opinions of members of the UTMB 
faculty and should not be used for purposes of diagnosis or treatment 
without consulting appropriate literature sources and informed professional 
opinion." 


INTRODUCTION

The creation or restoration of an aesthetically pleasing facial contour
can encompass many surgical approaches.  Rhinoplasty is probably the most
frequently performed procedure that has a marked effect on the facial
appearance, but rhinoplasty alone is sometimes inadequate.  Successful
facial plastic surgery requires the surgeon to achieve a "balanced" facial
appearance that takes into account more than the nasal profile.  Chin and
malar augmentation can play a major role in achieving this balanced look.


As an adjunct to rhinoplasty, chin implantation has long been a valuable
technique.  It can be especially important in creating an aesthetic
profile when combined with rhinoplasty, as a poorly developed or
proportioned chin frequently accentuates nasal deformities.  The malar
prominence areas dominate the lateral midface and their importance is
paramount in the "social profile" or oblique view.  Augmentation of this
area can provide a more youthful appearance and softens the more angulated
face that may appear drawn or harsh, especially when performed in
conjunction with rhytidectomy and/or blepharoplasty.

The submalar area deserves special mention as this area is not emphasized
in most of the literature reviewed that discusses malar augmentation.
Malar flattening and submalar hypoplasia is most common in caucasians.
Underdevelopment of the submalar area gives rise to the emaciated "hollow"
facial appearance.  The decrease in submalar soft tissue that occurs with
subcutaneous fat atrophy as the face ages can exacerbate the problem.  The
deficiency here can be subtle and camouflaged by sagging of facial skin,
but post- rhytidectomy results can appear tense and "stretched" over the
inadequate submalar area.  Further, augmentation of the malar area can
exaggerate this deformity, so preoperative assessment is the key to
success.  A slight fullness of the submalar area imparts a youthful look
and softens the overall appearance.  Submalar augmentation can be
intuitively included in the discussion of malar augmentation that follows.


Aside from purely cosmetic surgery, both the malar and chin augmentation
principles and techniques are valuable in restoring post traumatic and
congenital facial disfigurement.

Facial contour modification can be performed through craniofacial or
orthognathic surgical rearrangement of the facial skeleton, or through the
use of implanted material.  For the purposes of this review, only
implantation will be addressed.  Orthognathic problems and malocclusion
should be addressed before mentoplasty is proposed, but the great majority
of patients are usually reluctant to undergo orthognathic surgery.  Most
just want cosmetic augmentation, but they should at least be counseled
prior to proceeding.

CONTRAINDICATIONS

Perhaps as important as knowing when to perform these procedures is
knowing when they are not indicated.  It is generally agreed that it is
not appropriate to use implantation alone for correction of severe
micrognathia or retrognathia (3rd degree retraction - see below).
Additional "relative" contraindications to routine mentoplasty include the
patient with a very short mandible or a disproportionately short maxilla
Schoenrock outlines several contraindications to malar augmentation.  In
addition to avoiding augmentation of the malar area of patients who really
have submalar deficiency, he advises against this procedure in patients
with small nasal and mental features, those who have prominent noses with
small chins (unless chin augmentation is also planned), and patients with
"deep- set" orbits in whom augmentation may exaggerate the appearance.
Overall, a common sense approach and thoughtful consideration of the
consequences that one change in facial region may have on the others is
the key to identifying potential pitfalls.


FACIAL ANALYSIS

Aside from a patient presenting to the aesthetic surgeon with a specific
request for malar or chin augmentation, the surgeon usually is the one to
recommend these procedures.  Frequently this will be during the
preoperative planning for a different procedure, such as rhinoplasty,
rhytidectomy, and/or blepharoplasty.  The evaluation of the preoperative
patient should take into account the effect of the planned procedures, and
currently available graphic imaging systems are excellent for this.  

Attractiveness is a subjective quality, and many people who are considered
"beautiful" have less than classic facial features in some aspects.  In
order to lend more objectivity to the process, the surgical community has
established certain characteristics that are considered aesthetically
pleasing.  Many authors have proposed methods of facial analysis to allow
surgeons to objectively evaluate their patients and thus plan surgical
alteration of their appearance.  Typically, detailed analysis of the
facial features of people considered to be highly attractive have been
used as the basis for these methods.

The method of facial analysis used by most aesthetic surgeons is one form
or another of cephalometrics.  This is nothing more than the formulation
of geometric analysis of anatomic relationships of the face and head.
Cephalometrics can be determined for "hard tissue" (skeletal) or "soft
tissue".  Soft tissue cephalometrics is the most commonly described in the
aesthetic surgery literature, while skeletal cephalometrics is probably
most useful for planning maxillofacial orthognathic or reconstructive
surgery.  To illustrate, if chin implantation is planned, soft tissue
landmarks could be used to determine the amount of augmentation and
therefore the size and shape of the implant, whereas if sliding
genioplasty were planned, skeletal cephalometric analysis would be
desirable.

ANALYSIS FOR CHIN AUGMENTATION

For chin augmentation, analysis of the soft tissue profile is the primary
tool.  Several authors have described methods of determining ideal chin
position and will be described.  No one method is "best", but some are
simpler than others.

Rish technique - A line perpendicular to the Frankfort Horizontal line is
projected tangential to the most anterior edge of the lower lip vermilion
border.  This perpendicular line is the meridian that marks the desired
chin projection.

Legan's angle - One line is projected through the glabella and the
subnasale, and a second line is projected through the subnasale and the
pogonion.  The ideal angle created between these two lines is 120 ñ 40.

Merrifield Z-angle - A line is projected through the pogonion and the most
anterior point of the upper lip vermilion border.  The angle this creates
with the Frankfort horizontal line should be 80o ñ 5o.

Zero meridian of Gonzales-Ulloa - A line perpendicular to the Frankfort
Horizontal line projected through the nasion.  The pogonion is supposed to
be within 5 mm of this line.  Slight (up to the quoted 5 mm) retraction of
the pogonion from this line is more acceptable in women as this creates a
softer more feminine profile.  Retraction of the chin up to 1 cm is deemed
1st degree retraction, from 1 to 2 cm is 2nd degree retraction, and
greater than 2 cm is classified as 3rd degree retraction.  The
significance of this is that 1st and 2nd degree retractions are treatable
with implants, but 3rd degree retraction is best treated with
maxillofacial surgery.

Goode's method - A perpendicular line is projected from the Frankfort
horizontal through the alar-facial cease.  The ideal chin position is said
to be at or just anterior to this line

Lower facial triangle - Drs. Calhoun and Gibson created the lower facial
triangle method of analysis, wherein a triangle is defined by the tragion
(consistent with the superior margin of the EAC), the subnasale, and the
chin defining point (determined by centering an arc at the tragion with a
radius that allows the arc to be tangent to the chin).  The points T, S,
and C are used, and based on comparative data, the ideal facial profile
was determined to have a TC/TS ratio of 1.15 to 1.19, and an angle "S" of
88 to 93 degrees.  Interestingly, the algorithm provided by the authors
proposes that this analysis be utilized only if the lower facial profile
was subjectively not well balanced.  In other words, if the facial
features were subjectively appropriate, no further analysis was
recommended.  The reported advantage of this method of analysis is that it
takes into account the height and horizontal balance of the lower half of
the face.


Peck and Peck - This method also takes into account facial height in
addition to anterior projections of facial profile features.  The nasal
angle is defined by lines from the tragion to the nasion and the nasal
tip.  The maxillary angle is defined by lines from the tragion through the
nasal tip and through the labrale superiorus.  The mandibular angle is
defined by lines from the tragion through the labrale superiorus and the
pogonion.  The ideal values for these three angles is 23.3, 14.1, and 17.1
degrees respectively.  The facial angle is then defined as the angle
created by the intersection of a line from the tragion through the
midpoint of a line from the nasion through the pogonion.  Dropping another
line from the nasion to labrale superiorus, through the aforementioned
line from the tragion, creates another angle, the maxillofacial angle.
Finally, the nasal maxillary angle is created by the intersection of the
projection from the tragion with a line drawn between the nasal tip and
the labrale superiorus.  The ideal facial, maxillofacial, and nasal
maxillary angles are said to be 102.5, 5.9, and 106.1 degrees
respectively.

Holdaway - The "harmony" line or "H-line" is a projection from the
pogonion through the most prominent portion of the upper lip.  The angle
between this projection and a line between the pogonion and the nasion is
called the "H angle".  The ideal H angle is 10 degrees and the higher the
angle, the more retrusive the chin.

Powell and Humphreys - This method uses "aesthetic triangle" and is based
on the ideal profile having a nasofrontal angle of 115/120 degrees
(male/female), a nasofacial angle of 36/36 degrees, a nasomental angle of
130/130 degrees, and a mentocervical angle of 80/85 degrees.  The
interrelationship of these angles can be appreciated by constructing them
on a facial profile and noting how changes in any one reference point can
affect the other angles.

Stambaugh - A straight line is projected tangential to the most anterior
point of the vermilion of the upper and lower lips with the lips when they
are in contact over the teeth.  The chin should meet this line in males
(+/- 2 mm) , and be 2 to 3 mm behind this line in females (+/- 2 mm).  As
stressed by Gibson and Calhoun, Stambaugh emphasizes that the vertical
height of the maxilla and mandible be considered when evaluating the
patient for chin augmentation.  If the mandible itself is short relative
to the rest of the face, augmentation may accentuate lower lip eversion.
If the maxillary height is disproportionately small, augmentation of the
mentum can accentuate a deep sublabial crease.  

ANALYSIS FOR MALAR AUGMENTATION

Despite the relative availability of literature about malar implantation
augmentation, there does not appear a very widely accepted standard method
of facial analysis to optimize preoperative planning.  Rather, the
definition of anatomic landmarks and methods of delineating the malar
prominence and boundaries is accompanied by a caveat that malar
augmentation should be offered when it will affect a greater harmony and
balance of facial proportions.  Perhaps the reason that standard facial
analysis is difficult to apply to malar areas is that two dimensional
projection analysis does not take into account the more important three
dimensional aesthetics of the malar mound.  In fact, the aesthetics of a
particular individual may supersede algorithmic analysis. Nevertheless, a
summary of some methods that can assist in evaluating the malar area
follows.

Hinderer - In a frontal view, draw a line from the lateral commissure of
the lip to the lateral canthus of the ipsilateral eye.  Another line
projects from the tragus to the inferior edge of the nasal ala.  The area
posterior and superior to the junction of these two projections should the
most prominent area of the malar eminence.

;Powell et al. - A vertical line is drawn through the middle of the face
and then the segment between the nasion and the nasal tip is bisected by a
line that curves gently upward to the tragus on both sides.  This line
demarcates the .  A line is drawn from the inferior ala to the lateral
canthus and another one, parallel to this one, is drawn from the lateral
oral commissure toward the ear.  The intersection of the curvilinear
horizontal line and the line from the oral commissure marks the point
where the malar area should be most prominent

Silver and Guilden - As general rule these authors suggest that if the
malar prominence in the true lateral projection is greater than 5 mm
posterior to the nasolabial groove then there is deficiency in the malar
area.  As a more formal method of analysis Silver describes the malar
prominence triangle.  To construct this triangle draw a Frankfort
horizontal line across the face in frontal projection, and a parallel line
that bisects the upper lip.  Then drop a perpendicular line through both
of these lines and through the lateral canthus.  The intersection of the
vertical line and the line through the upper lip defines "point A".
Project a line from point A though the medial canthus and then a second
line from point A towards the temporal area but at the same angle from the
vertical that was created by the projection from point A through the
medial canthus.  This creates the malar prominence triangle with the base
the Franfort line and the apex point A.  Silver advises that the implant
should be placed several millimeters below the Frankfort line.  

/Schoenrock - On an oblique view (27 to 35 degrees of rotation from the
frontal view) with the patient an a position to keep the Frankfort line
truly horizontal, a line drawn through lateral canthus and the mentum
should reveal the "width" of the malar eminence.  This is said to be about
3 to 7 mm in the average person, and therefore this gives the target for
augmentation purposes in the under developed malar area.  In evaluating
this area it appears that the author intends for the 3 to 7 mm dimension
to refer to the perpendicular distance from the projected line, and that
he is describing the width of the skeletal component excluding the soft
tissue covering.

Some authors confess that the best way to plan malar augmentation is to
use computer graphics software that allow the surgeon to directly
visualize the overall effect of malar augmentation on the video monitor.
One method is to use a prototype implant of the proposed size, taped to
the skin, and photograph the patient.  Then using the software
capabilities to shade the implant to match the surrounding skin, the
postoperative appearance can be simulated so that the patient can be
involved in the selection of the amount of augmentation.  Whatever method
is used, careful scrutiny of the submalar area should be performed.
Flattening of the submalar area is sometimes more causative of midfacial
disharmony than is malar flattening, and as noted previously, augmenting
the malar area in these instances will only enhance the deformity.


IMPLANT SELECTION

There are a variety of implantable materials available.  Implant materials
have been the subject of a great deal of scrutiny in the past few years
particularly silicone based products, which is important as this has
historically been one of the more popular materials for chin and malar
implants.  The jury is literally and figuratively still out on this topic
so any surgeon should familiarize himself with the available options.
Autogenous implant materials do circumvent the problem of biocompatibility
but also carry the price of donor site morbidity, absorption in some
cases, and prolonged surgical procedures (harvest and donor site closure
time in addition to normal implant time).

The key factor in implant behavior is the tissue/implant interface and
this interface may change in reaction to the forces of the biologic
environment.  As originally proposed by Scales, the ideal implant material
should behave according to the following criteria:

it should not be physically modified by soft tissue
it should not incite foreign body reaction
it should not incite an allergic response or induce hypersensitivity
it should be non-reactive chemically
it should be noncarcinogenic
it should resist deformation secondary to strain (it should be "elastic"
not "plastic") it should be sterilizable it should be capable of being
fabricated or modified to the desired form easily.

No man-made material has been found that meets all the criteria, but some
come reasonably close.  

METALS All metals corrode to some degree in the human body.  The
implant/tissue interface is the site of this action and with the initial
reaction, there is the formation of an oxide film which actually changes
the characteristics of the interface and thus the process is retarded to
some extent.  Stainless steel was the first metal to be used extensively,
but it does corrode.  Vitallium was introduced in the 1920's and is an
alloy of cobalt and chromium.  Like all chromium alloys, it has more
corrosion resistance than stainless steel but is not corrosion proof.
Titanium is a bit more corrosion resistant than Vitallium.  In general
metals are used to restore or change skeletal framework and are not often
used to support soft tissue augmentation.  

POLYMERS Polymers are carbon chain based molecules with varying degrees of
crosslinking, which is the origin of their varied mechanical properties.
This category includes the dimethylsiloxanes (or "silicone" based
molecules), polytetrafluoroehtylene (Teflon), Nylon, polyethylene,
polyamide, polymethylmethacrylate, and polyethylene terephthalate.  These
are the most widely used synthetic implant materials in facial contour
surgery.  All of the materials when used in bulk induce a fibrous capsule
formation around the implant.  However, because these materials can have
textured surfaces and can be woven they can be "incorporated" into the
implant site by fibrous "ingrowth" which is a nice way of saying they
promote a dense scarifying reaction that can hold them in position.
Composite polymeric implants such as a silastic chin implant with a dacron
backing to promote tissue ingrowth to help secure the implant and avoid
migration are also available.

Silicone based products - silicone is a natural occurring substance in the
body, found in mucopolysaccharide.  Depending on the degree of
crosslinking, it can be formulated as anything form an injectable liquid
to a dense rubber like consistency.  It is relatively inexpensive and can
be carved, or purchased in premolded implant shapes.  It has been the most
popular chin implant material but some question its use due to erosion of
the mentum after years of pressure when implanted in its more firm form.
An alternative to the solid form is the use of prefabricated silastic bags
filled silicone gel, which according to some has not shown any evidence of
the tendency to cause erosion of underlying bone.  The drawback of this
approach is the limitation in the size and shape of the implant
commercially available.  Despite this it is widely used.

Polyamide - Supramid is a commercially available mesh that is related to
Nylon and Dacron.  It promotes a fairly intense foreign body reaction that
causes a dense scarifying reaction, making it very difficult to remove one
healed in place, but also giving it stability.  It has not been reported
to be associated with bone resorption, and can be custom shaped through
folding or stacking pieces of the material together.

Polyethylene and Polyethylene terephthalate - Mersilene is a mesh similar
to supramid, but made of polyethylene terephthalate (also known as
Dacron), and touted to be a good material for facial contouring.
McCollough is a proponent of rolled mersilene implants in facial
augmentation.  It promotes a less intense tissue reaction than Supramid.
Medpor is the trade name for a relatively new polyethylene polymer that is
porous.  It has a pore size of between 135 and 250 micrometers.
Theoretically a pore size of greater that 100 micrometers will allow
osseointegration and soft tissue ingrowth into the implant, which would be
ideal for facial implants.  There are however some conflicting data
concerning osseointegration of this material.  However, it has minimal
disadvantages and is available in preshaped implants or as a block form
that can be carved to custom sizes.

Polytetrafluoroethylene (PTFE or Teflon) - Proplast I was the first
biosynthetic material specifically designed for implantation, and is a
black solid composed of carbon fibers and teflon.  Proplast II (which is
white), is mixture of teflon and aluminum oxide (instead of carbon
fibers).  Both versions of Proplast are porous, allowing for some tissue
ingrowth, and can incite fairly aggressive inflammatory reactions that
last for months.  They are not however noted to have a high infection or
extrusion rate.  Proplast material is available in commercially preshaped
implant sizes, but can be carved with some difficulty.  Although the
Proplast II was developed to allow its use in areas covered by thinner
skin because it is less likely to show through, it is a harder material
and more difficult to carve than Proplast I.

Polymethylmethacrylate (PMMA) - PMMA is a hard polymer that is frequently
used in bony reconstruction of skull defects, it can be used as a facial
contour implant.  Gonzales-Ulloa, who was one of the pioneers of chin
implants, uses it by choice and claims to have never experienced an
extrusion or even a significant complication in 38 years.  It can be
purchased in preformed implant form, or fashioned intraoperatively in a
cold-curing form.  The cold-curing form comes as two components,a liquid
monomer and a methylmethacrylate powder.  These are mixed together and a
polymerizing reaction takes place creating a temporarily malleable mixture
that is then custom shaped and trimmed to fit the needs of the surgeon.
This form is not especially useful for implantation when the introducing
incision is small, as in most malar and chin implant cases.  There is also
the risk of side effects sometimes seen due to the toxicity of the
monomeric component, although this is rare.  Nevertheless it has some
excellent qualities such as superior biocompatibility and tissue ingrowth
promoted by drilling multiple holes in the implant.  The preformed version
can be cut and shaped with rotary burrs.

HTR - "Hard Tissue Replacement" and is a trademark of the company that
developed this composite material.  It consists of a core of PMMA,
surrounded by a coating of polyhydroxyethylmethacrylate (PHEMA) and
calcium hydroxide.  The intention is to create a hydrophilic outer layer
that is capable of being osseointegrated.  The absorption of water in the
outer layer is accompanied by the presence of calcium ions carrying a
negative charge.  It has been shown that negative surface charge at the
interface of healing bone enhances new bone growth, by mechanisms that are
not clear.  HTR has been used successfully in humans, but whether it
delivers on the aspect of osseointegration is not agreed upon.  There does
appear in some studies to be a bilaminar fibrous capsule intimately
associated with the implant with bone growth surrounding it in some cases
(osseoconduction), but actual bone growth into the outer layer of the
implant has only been reported in one animal study.  HTR comes in block
form, granule form (can be used to fill defects and irregular surfaces),
or in preshaped implants.  It is more difficult to custom shape and drill
than most other polymers.

Bioplastique - Dr. Robert Ersek has reported the only use of this material
in human subjects.  Bioplastique is a biphasic mixture of textured 100 and
600 micrometer particles of vulcanized methylpolysiloxane in a gelatinous
carrier vehicle.  The gel is a "plasdone" and is readily absorbed by the
body and excreted unchanged by the kidney.  Dr. Ersek has used the
material for chin augmentation to in 13 patients.  A "pocar" is used to
create an array of subcutaneous tunnels above the layer of the periosteum.
The pocar is introduced through a puncture made on the opposite side of
the mentum, and the tunnels are created in a radial fashion through this
puncture.  The procedure is performed bilaterally and a special injection
gun and cannula system is used to deliver the Bioplastique mixture through
the puncture into the subcutaneous tunnels.  The amount of material is
based on the judgement at the time of injection, and irregularities are
"digitally" manipulated into smooth contour during the first postoperative
week.  There have been no reported adverse effects and no loss of
augmentation in follow up, although the longest period is reported as five
years.  The augmentative effect is not thought to be due to the material
itself, but rather to the development of multitudes of fibrous capsules
around the minute particles.

SYNTHETIC BONE GRAFT MATERIALS Synthetic bone graft materials are intended
to be incorporated into the host bone structure either through
osseointegration or osseoconduction.  The principle is that no intervening
fibrous layer is supposed to exist between the implant and the host bone.
There is some question

IMPLANT SIZE

When planning orthognathic and maxillofacial procedures that rearrange the
facial skeleton, it is common to use a 1.0 : 1.0 dimensional ratio in
predicting the post surgical effect of a change in bone structure on soft
tissue facial contour.  Kent has found that with implant materials, a
ratio of 1.0 : 0.7 more accurately predicts the final result (about two
years post-op); that is if you select an implant that is 1 cm thick, you
end up with a 0.7 cm increase in soft tissue projection eventually.  The
loss of dimension comes from position shifts with settling or shifting of
the implant, bone resorption (although this occurs over an extended period
of time), and soft tissue thinning as it is stretched over the implant..

The size of the implants is selected based on the preoperative facial
analysis, although the malar implant sizing is more subjective than the
chin implant size.  For chin implants the method to determine the width of
the implant is not set in stone, and the surgeon's judgement with respect
to lateral "tails" is the deciding factor.  The length of the lateral
portion of the chin implant can be used change the overall appearance of
the jawline.

There are a number of commercially available preformed implants available
for facial contouring.  They come in various sizes and materials, and a
complete discussion of these is not necessary.  However, some research by
the surgeon into the available products might save a great deal of
intraoperative implant modification time.


SURGICAL TECHNIQUES

CHIN IMPLANTS

For chin implants, the majority of authors reviewed prefer an extraoral
submental approach to implantation.  Their reasons are that this avoids
contamination form oral flora, and is associated with less post-operative
morbidity for the patient.  Stabilization of the implant is also said to
be more difficult when the intraoral approach is utilized.  However,
Gonzales- Ulloa uses the intraoral approach and reports no increased
incidence of infection or extrusion.  He places a PMMA implant in an
intramuscular plane of dissection , and uses a periosteal "U" stitch to
secure its location.  This method seems attractive, but nevertheless, the
majority of authors report the preference for an extraoral procedure.

For the extraoral approach, a small submental horizontal incision is made
just posterior to the first submental skin crease.  This is carried down
to periosteum, which is incised along the inferior surface of the mandible
on both sides of the midline.  the periosteum is then elevated carefully
superiorly and a bit laterally, taking care to avoid damage to the mental
nerves (remember that the mental nerves exit the mandible about 25 to 27
mm lateral to the midline).  The periosteum is elevated to create a pocket
slightly larger than the implant to allow easier insertion.  The implant
is placed in the subperiosteal pocket and care should be used to keep the
implant as inferior as possible.  Most authors recommend some method of
stabilization or fixation of the implant to avoid superior migration which
might lead to accelerated bone erosion of the anterior mandible.  

Supra vs subperiosteal implantation is an area of some controversy, with
some claiming that subperiosteal implantation leading to more bone
resorption underlying the implant.  Supra periosteal implantation is an
acceptable method, and some even perform a composite type of technique
wherein they incise the periosteum laterally and elevate small tunnels in
which to insert the "tails" of the implant, leaving the central portion of
the implant above periosteum.


MALAR IMPLANTATION Malar implantation can be performed through a an
intraoral "canine" type incision, a lateral subciliary skin/muscle flap
approach, transconjunctivally, or via a rhytidectomy approach.  The method
used depends on the surgeon' skill and preference.

The intraoral approach probably provides the best exposure of the malar
and the submalar areas.  An incision is made in the soft tissue overlying
the maxilla near the canine fossa similar to one used for a Caldwell-Luc
procedure.  The periosteum of the maxilla is elevated up to the malar
area, taking care to avoid injury to the infraorbital nerve.  The
elevation is performed only as much as is necessary to introduce the
implant as the subperiosteal pocket created will allow less movement of
the implant if it is snug.  Nevertheless, this approach has apparently
allowed more mobility than others because it is the only approach where
fixation of the implant stressed.  One method of fixation is transfixion
sutures, either through the overlying skin with the ends tied over a soft
bolster or "external" splint, or suspension sutures triangulated through
the superior/posterior aspect of the implant , passed blindly through the
hairline and secured over a bolster.  The transfixtion or suspension
sutures are removed after three or four days.  Alternatively, in the case
of a rigid implant, a screw can be used to directly fix the implant to the
underlying bone.

The transconjuctival or subciliary approaches can be used independently or
in combination with blepharoplasty.  A standard transconjunctival approach
allows access to the inferior and lateral orbital rims, and sharp
dissection here followed by periosteal elevation allows the creation of a
pocket to accept the implant.  The subciliary technique is similarly
performed, but does create a minimal facial scar.  Neither technique
requires fixation of the implant, but both require (or at least it is
recommended) a flexible implant material such as Silastic to be used
because the incisions used are so small.  Shoenrock uses this technique
and recommends a textured Dacron backed Silastic implant (commercially
available) to allow fibrous tissue ingrowth and adherence to maintain the
position of the implant.

The rhytidectomy approach is advocated by those with experience in its
use.  It does put the frontal branch of the facial nerve at some risk,
although proponents state that blunt dissection posterior to and parallel
to the nerve is safe.  This requires identification of the nerve and
failure to do so would make this procedure less safe.  If the nerve is
found, the blunt dissection is carried down to bone, and the periosteum of
the anterior zygomatic arch and malar prominence is elevated, creating a
small pocket for the prosthesis.  Again fixation is not possible, but a
porous or predrilled implant is used by the advocates of this technique to
encourage tissue ingrowth.


COMPLICATIONS

In addition to the possible complications of any surgical procedure
(bleeding, hematoma formation, injury to nerves, infection, etc.), are the
risks of implant migration and or extrusion, and bone resorption.
Fortunately the rate of postoperative complication after chin and malar
implantation is reportedly very low.  Infection is a particularly dread
complication as it can lead to forced removal of the implant it
antibiotics are not effective.  Fortunately again, the incidence of
postoperative wound infection ultimately requiring implant removal is very
low.  To help prevent this some authors recommend soaking the implant,
especially the porous ones in antibiotic solution up until actual
implantation.  Some commercially available implants have been impregnated
with antimicrobials.

Bone resorption under the implant is a controversial topic and there are
conflicting reports concerning this occurrence.  Implant characteristics
do play a role in this with general agreement that the more firm the
implant material the more likely there will be bone significant erosion.
Some have suggested that subperiosteal implantation is more likely to lead
to this complication.  Supraperiosteal implantation may be more
advantageous, but it also predisposes to increased implant mobility and
this in itself is believed to be one of the causes of complications like
infection, migration, and extrusion.  As noted previously, a composite
approach wherein part of the implant is subperiosteal and part is
supraperiosteal may be useful and has been described for chin implants.
Malar implants do not seem to be as subject to migration problems,
probably due to less dynamic forces imparted on them as compared to chin
implants.

An additional complication, or at least the fear of this complication, has
surfaced in recent times.  This is the concern over the possibility of
induced collagen-vascular illnesses secondary to silicone based implants.
The most recent data does not support the statistical connection of this
connection, but fear over potential malpractice claims has not been
quashed completely.  Surgeons will have to make this choice based on their
experience and the results of ongoing studies and litigation.

-------------------------------------------------------------------------
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