TITLE: Microtia Reconstruction
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: October 13, 2004
RESIDENT PHYSICIAN: Jing Shen,
MD
FACULTY PHYSICIAN: Francis B. Quinn, Jr., MD
SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD
"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
Microtia occurs once in
about every 7,000 to 8,000 births in the general population. It occurs more often in right ears and males,
especially in unilateral microtia. The
occurrence in general is more often in Hispanics and Asians than blacks and
whites. The cause of microtia is
multifactorial. Fewer than 15% of the
cases have a positive family history. (1) And it is fairly common for microtia
to be associated with other congenital abnormalities. Among associated malformations, facial cleft
and cardiac defects are the most common followed by anophthalmia or
microphthalmia, limb reduction defects, severe renal malformation, and
holoprosencephaly. (2) And it has long
been felt that microtia represents the mild end of the spectrum of hemifacial
microsomia, with Goldenhar syndrome being the severe end of the spectrum.
(2) There are many classification
systems for microtia. One widely adopted
system assigns a grade from I to III based on the severity of the
deformity. Grade I represents a pinna
with all anatomic subunits present but misshapened. Grade II represents a pinna with some
recognizable subunits but is rudimentary and malformed. Grade III includes the classic “peanut” ear,
which is severely deformed with an inferior fibroadipose lobule and a nubbin of
cartilage in the superior remnant. (6)
Microtia reconstruction is
one of the most challenging surgeries faced by the reconstructive surgeon. Dr. Tanzer published a paper on the use of
autogenous rib cartilage in reconstruction of the auricle in 1959 and brought
in the new era of auricular reconstruction.
Dr. Brent modified Dr. Tanzer’s technique and has been treating patients
with auricular malformation since the 1970s.
He has treated over 1,000 patients with microtia in the last 25 years
and has become the foremost expert in microtia reconstruction. Another popular technique based on a modification
of Tanzer’s technique was developed by Dr. Nagata
from
Surgical Planning
The timing of microtia reconstruction has been much
debated in the literature. Factors used
to determine the most appropriate timing for auricular reconstruction include
the age of external ear maturity, the availability of adequate donor site rib
cartilage, and psychological impact of the disease. (2) At birth, the auricle is 66% of its adult
size. By age 3, it is 85% of its adult size.
By age 6, it is 95% of its adult size.
Rib cartilage is rarely of sufficient size until age 5 or 6 years. And per Dr. Brent’s experience, the
psychological effects of microtia are important once a child starts school. Therefore, Dr. Brent starts his auricular
reconstruction at age 6 in general.
About 60-70% of his reconstructions were done between age 6 and 10. (5)
Dr. Nagata starts his reconstruction at age 10 and a chest circumference
of at least 60cm, which can be confirmed with X-ray. (4) This may be related to
the relative large volume of cartilage needed for using his technique for
reconstruction.
A complete audiologic
evaluation and radiographic study of the temporal bone is critical in all
patients with microtia. The predominant
hearing deficit in microtia is conductive hearing loss. However, sensorineural hearing loss has also been
found in 10-15% of patients.(2) A normal
middle ear is rarely found in conjunction with microtia. The status of the middle ear is not directly
related to the external deformity. The
severity of the external deformity appears to correlate with the severity of
the temporal bone abnormality; but no association between the severity of the
dysmorphic features and the degree of hearing loss has been found. Otologic surgery has traditionally not been
performed for unilateral microtia with normal hearing in the other ear. This is because the patients often do not
obtain true binaural hearing after otologic surgery. And also because of the belief that the
auditory neural structures critical for binaural processing develop only if
binaural hearing is present early in life.
However, one recent study suggested that unilateral hearing loss
increases the risk for speech and language delay, attention deficit disorder,
and poor performance in school. And the
plasticity in the developing auditory system may be greater than originally
suggested. Therefore, there has been an
increased interest in atresia correction.
If otologic surgery is to be performed on the microtic ear, it is
important to have careful coordination between the otologist and the
reconstructive surgeon. Dr. Brent
prefers to have the otologic surgery after the completion of the auricular
reconstruction to avoid the disruption of the vascular supply. And this has been the standard approach to
management in most patients.
Brent Technique (3)
This is a 4- stage procedure.
First stage: Auricular framework fabrication with
contralateral rib cartilage
A template is made by placing a piece of X-ray film
against the normal ear in the unilateral cases or the parent’s ear in bilateral
cases and tracing all anatomic landmarks.
The template is then made several millimeters smaller to accommodate for
the thickness of the skin cover and overgrow potential of the reconstructed
ear. (5) The contralateral 6th,
7th and 8th costal cartilages are usually harvested. The base of the framework is carved from the
synchondrosis of the 6th and 7th rib cartilage. The helix is carved from the “floating” 8th
rib cartilage. The helix is then sutured
to the base with clear nylon suture. The
fabricated framework is then positioned in a subcutaneous pocket through an
incision at the posterior and inferior border of the vestige. An extra piece of cartilage is also banked
either in a pocket posterior to where the framework is placed or underneath the
chest incision to be used in the later stage for improved ear projection. Two small suction drains are placed and left
for 5 days.
Second stage: Lobule transposition
This is performed several months after the stage I
procedure. The lobule is mobilized as an
inferiorly based tissue flap and rotated to receive the end of the
framework. Unused lobule tissue is
excised.
Third stage: Auricular framework elevation
An incision is made several millimeters from the
margin of the rim. Dissection is carried
over the capsule of the posterior surface of the construct until the correct
amount of projection is achieved. The
backed piece of cartilage is placed between the framework and the mastoid to
stabilize the ear position. A split
thickness skin graft is used to cover the back of the elevated cartilage
framework.
Fourth stage: Tragus construction
A composite skin/cartilage graft is taken from the
anterolateral conchal surface of the normal ear. A J-shaped incision is made along the
posterior tragal margin. The composite
graft is placed through the incision and positioned so that it produces both
projection of the tragus and cavitation of the retrotragal hollow. Soft tissue also is removed from the new
concha to deepen the concha bowl. The
shadow of the neotragus imitates an external auditory canal. Frontal symmetry is also addressed at this
stage.
Recent modification:
The most recent modification is to incorporate a small
cartilage into the framework to create a tragus in stage 1. It is sutured to the inferior aspect of the
framework to create an antitragus, then curved around and attached to the crus
helix with a bridging mattress suture superiorly to create a tragus.
Major Criticism:
1)
Number of stages required to achieve the final
result.
2)
The aesthetic result from the tragus reconstruction
3) Effacement of the postauricular sulcus causing decreased projection of the reconstructed ear
Nagata Technique (3)
This is a 2-stage procedure.
First stage: fabrication of auricular framework, tragus
reconstruction and lobule transposition
Ipsilateral costal
cartilages of the 6th, 7th, 8th and 9th
ribs are harvested. The base of the
framework is carved from the synchondrosis of 6th and 7th ribs. The helix and crus helix are carved from the
8th rib. The 9th
rib is used to construct the superior crus, the inferior crus, and the
antihelix. The remaining structures are
carved from residual cartilage pieces.
The cartilage framework is assembled with fine-gauge wire suture. Most of the posterior perichodrium is left
intact to minimize the anterior chest wall deformity. An incision is made at anterior surface of
the lobule. A 2mm circular portion of
the skin is removed at the end of the incision.
A W-shaped incision is also made at posterior lobule to divide the
lobule into an anterior tragal flap and posteroanterior lobular skin flaps. A subcutaneous pocket is dissected through
this incision. The central portion of
the posterior skin flap is not elevated to augment blood supply to the skin
flap. The framework is then placed in
the pocket. The posterior flap is then
advanced to suture to anterior tragal flap and the lobule is transposed by
assembling the flaps in the Z-plasty fashion.
The small circular skin defect gives rise to incisura intertragica. Bolsters are used to approximate skin flaps
to the framework, and the bolsters are left in place for 2 weeks.
Second stage:
framework elevation
Six months after the first stage, a crescent-shaped
piece of cartilage is harvested from the 5th rib through the previous
chest incision. An incision is made 5mm
posterior to the margin of the construct.
The framework is elevated and held in place by wedging the newly
harvested cartilage into position. A
temporoparietal fascia flap is elevated through a new scalp incision and
tunneled subcutaneously to cover the posterior surface of the cartilage graft
and reconstructed auricle. The back of
the framework is then covered with ultra-delicate split thickness skin graft
harvested freehand from the occipital scalp.
Advantage: more natural and deeper conchal bowl.
Major criticism:
1)
Vascular compromise of the peri-lobular flaps
from manipulation, increasing the risk of flap necrosis
2)
Considerable amount of cartilage required by
this technique
3)
High extrusion rate may be due to use of wire
suture
4)
Temporoparietal fascia
used in every case with risks of scalp scarring, temporal hair thinning, and
making it unavailable for future possible salvage of complications
5)
Frontal symmetry not addressed
Complications:
The immediate complications at the chest wall donor
site include pneumothroax and atelectasis.
The delayed complications include anterior chest wall deformity and
scarring. The chest wall deformity was
observed more often in younger children then in older children. Dr. Nagata has recommended keeping posterior perichondrium
intact to help prevent this problem. (3)
The complications at the ear reconstruction site
mainly consist of extrusion of the framework secondary to skin flap necrosis
and resorption of the framework. If the
framework is exposed, early intervention with local skin and fascial flaps is
usually used to salvage the reconstruction.
The temporal fascia is a potential salvage resource. Also, suture placed too tightly or placement
of the framework in a scarred, ischemic bed may predispose the cartilage to
resorption. (3)
Alloplastic reconstruction
There has always been interest to find an alloplastic
material to reconstruct the microtic ear and provide a more consistent
aesthetic result while avoiding donor site morbidity. Also without the limitation of the size of
the rib cartilage, the reconstruction may start at an earlier age.
Cronin and Ohmori have
described the use of the Silastic framework for auricular reconstruction.
(2) They had excellent initial
results. But the long term follow up
showed a high incidence of implant exposure.
Also minor trauma or abrasions resulted in implant exposure and
failure. Therefore the use of silicone
for auricular reconstruction has been abandoned
More recently Reinisch has
proposed to use porous polyethylene (Med pore) in microtia reconstruction. Good short-term (2 years) results were
reported. Romo also reported that using temporoparietal fascia flap that
completely surrounds the Med pore implant appears to have significantly reduced
its failure rate. (1)
Prosthetic reconstruction
The osseo-integrated
anchoring device uses a titanium fixture to provide direct structural
connection between living bone and a load carrying implant. It was approved by the FDA to be used extra-orally
in 1995. It has been used more
frequently in Europe than in the
Even though prosthetic reconstruction usually involves
less surgery, the prosthesis must be replaced every 2 to 5 years. In addition, the skin/implant interface is
prone to irritation, therefore meticulous hygiene is necessary. Minor trauma may lead to infection. Lastly the prosthetic reconstruction
precludes future autogenous reconstruction because all ear remnants and skin
and soft tissue in the region are removed.
Tissue Engineering
Tissue engineering offers the potential to grow
autogenous cartilage in a precisely predetermined shape. This method can offer the advantage of
autogenous reconstruction without the morbidity associated with rib harvest. Cao et al. (1) transplanted bovine
chondrocytes onto a synthetic scaffold in the shape of the human ear and
implanted this in mice. The specimens
harvested at 12 weeks after implantation demonstrated new cartilage formation
and gross shape of the complex structures of the human ear. The scaffold appears to be critical. It has to be strong enough to maintain its
shape over time and also has to avoid extrusion. Furthermore, a significant amount of human
chondrocytes must be replicated from a small amount of cartilage. Human chondrocytes have been extracted from a
number of sources, including rib and ear.
In Vitro they have demonstrated ability to multiply well and form
new cartilage. (3) However, the
durability of this neocartilage remains unclear. Even though a tissue engineered framework is
not yet a practical option in auricular reconstruction, the technology and
concept are promising.
Bibliography