Download CME Auricular Reconstruction for Microtia: Part I. Anatomy

CME
Auricular Reconstruction for Microtia: Part I.
Anatomy, Embryology, and Clinical Evaluation
Elisabeth K. Beahm, M.D., and Robert L. Walton, M.D.
Houston, Texas, and Chicago, Ill.
Learning Objectives: After studying this article, the participant should be able to: (1) Understand external ear anatomy
and embryology. (2) Develop an approach to evaluation of microtia, including otologic considerations.
branches. Cervical nerves (the great auricular
nerve, C2 to C3) and the lesser occipital nerve
(C2) innervate the posterior aspect of the auricle and lobule. These nerves have a variable
size and distribution, but in the majority of
dissections, the lesser occipital nerves have
been found to be dominant and innervate the
superior ear and the mastoid region, whereas
the inferior ear and a portion of the preauricular area are supplied by the great auricular
nerve.2 The anterior surface and the tragus are
supplied by the trigeminal nerve (auriculotemporal nerve V3). The auricular branch of the
vagus nerve (Arnold’s nerve) provides sensibility to the external auditory meatus (Fig. 2).
In the first of a two-part series, we review
issues pertinent to the anatomy, embryology,
and criteria for comprehensive management
of children with microtia. The salient aspects
of external ear anatomy, including the nerve
and blood supply, lymphatic drainage, and aesthetic anatomic relationships, are described.
An overview of the embryologic development
of the external and middle ear and its relationship to auricular deformities is presented. The
clinical spectrum of microtia and its classification are discussed. The appropriate initial evaluation of these patients and the rationale and
criteria for middle ear surgery are reviewed.
Options for treatment, optimal timing, and coordination of the otologic and plastic surgical
management of these children are discussed.
The surgical techniques for external ear reconstruction, including autologous and prosthetic
methods, both historic and contemporary, are
briefly discussed.
Vascular Supply
Two separate but intercommunicating arterial networks derived from the external carotid
system supply the auricle.3 One network supplies the triangular fossa-scapha, and the other
supplies the concha. The triangular fossascapha network is derived from one subbranch
of the upper auricular branch of the superficial
temporal artery and from branches of the posterior auricular artery, which come through
the earlobe and triangular fossa and over the
helical rim. The conchal network is derived
from perforators (usually two to four vessels) of
the posterior auricular artery. The superficial
temporal artery also sends several small auricular branches to supply the anterior surface of
the ear. The rich communications between the
superficial temporal and postauricular arterial
EXTERNAL EAR ANATOMY
The external ear is composed of three primary components, the helix-antihelical complex, the conchal complex, and the lobule.
The three-dimensional relief of the ear is supported by the auricular cartilage, which is composed of highly convoluted elastic cartilage1
(Fig. 1).
Nerve Supply
Sensibility of the normal external ear is derived from several cranial and extracranial
From the Department of Plastic Surgery, M. D. Anderson Cancer Center, and Section of Plastic Surgery, University of Chicago. Received for
publication August 13, 2001; revised November 16, 2001.
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FIG. 1. (Left) External ear anatomy. CH, crus helicis; H,
helix; T, tragus; AT, antitragus; L, lobule; A, antihelix; TF,
triangular fossa; SC, superior crus; C, cavum conchae; CY,
cymba conchae; TA, tuberculum auriculae. (Center) Ear elastic cartilage anatomy, anterior surface. LT, lamina tragi; CU,
cauda helicis. (Right) Ear elastic cartilage anatomy, posterior
surface. TS, transverse sulcus; P, ponticulus.
systems allow for either system to support the
ear. Venous drainage flows through the posterior auricular veins into the external jugular,
the superficial temporal, and the retromandibular veins (Fig. 3).
PLASTIC AND RECONSTRUCTIVE SURGERY,
June 2002
vertical axis of the face at an angle ranging
from 2 to 30 degrees. The axis of the ear and
the nasal bridge, although similar, are not
identical: the angle between them approximates 15 degrees, with the ear more vertical.
The helical rim protrudes 1 to 2 cm from the
skull, with the projection increasing from superior to inferior. In a normal ear, the rim is
positioned 10 to 12 mm from the mastoid at
the superior helix, 16 to 18 mm from the mastoid at midear, and 20 to 22 mm from the
mastoid in the lower third. Although these
measurements are most commonly used as a
reference in setback otoplasty to avoid the classic “telephone” deformity, they must also be
carefully assessed and reproduced for an anatomically correct ear reconstruction in patients
with microtia.
Embryology
Both the first (mandibular) and second (hyoid) branchial arches contribute to auricular
Lymphatic Drainage
The lymphatic drainage patterns of the external ear are generally felt to reflect embryologic development. As such, it has traditionally
been considered that the concha and meatus
drain into the parotid and infraclavicular
lymph nodes, whereas the external auditory
canal and superior auricle drain into the mastoid and superior cervical lymph nodes.4 Recent use of sentinel lymph node biopsy and
lymphoscintigraphy in melanoma and other
neoplastic disorders, however, has demonstrated lymphatic drainage patterns in the
head and neck that are more unpredictable
and less discrete than those described
classically.5–7
Muscles
The anterior, superior, and posterior auricularis muscles constitute the extrinsic musculature of the external ear. The intrinsic musculature is largely vestigial and includes the
helicis major and minor, the tragicus, the antitragicus, and the transverse and oblique muscles1 (Fig. 4).
Anatomic Relationships
The relationships, dimensions, and proportions of the external ear have been thoroughly
reviewed by Tolleth8 (Fig. 5). Ear width is approximately 55 percent of length. The long
axis of the ear is tilted posteriorly from the
FIG. 2. (Above) Sensory innervation of anterior surface of
the external ear. (Below) Sensory innervation of posterior
surface of the external ear.
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AURICULAR RECONSTRUCTION FOR MICROTIA
FIG. 3. (Left) Arterial supply of the anterior auricular surface. The superficial temporal artery (STA) has upper, middle, and lower terminal branches, the most superior (*) of
which provides an anastomotic network to the anteroauricular surface with branches of the posterior auricular artery that
penetrate anteriorly in the region of the triangular fossa (‘),
concha (F), helical margin, and lobule (). (Center) Arterial
networks of the anterior auricular surface. The superficial
temporal and posterior auricular arteries contribute to the
triangular fossa-scapha network (vertical slashes) and the conchal network (horizontal slashes). (Right) Arterial supply of the
posterior auricular surface. Branches of the posterior auricular artery (PA) penetrate the cartilage at the triangular fossa
(‘), cymba conchae, helical root (*), cavum conchae (F),
and lobule () to anastomose with branches of the superficial
temporal artery. (Adapted from Park, C., Lineaweaver, W. C.,
Rumly, T. O., et al. Arterial supply of the anterior ear. Plast.
Reconst. Surg. 90: 38, 1992. Used with permission.)
development. The pinna begins developing between the third to sixth weeks of embryonic
life, when hillocks appear on the arches, and is
fully formed by the fourth month. The anterior
three hillocks, derived from the first arch, form
the basis of the tragus, the helical root, and the
superior helix. The second arch contributes
the posterior hillocks, which develop into the
antihelix, antitragus, and lobule. The pinna
develops around the external meatus, which
begins to canalize at week 28 (Fig. 6). The
cavity of the middle ear begins to form in the
first pharyngeal arch at 4 weeks. The middle
ear cleft is present at 8 weeks, and the cavity is
fully formed at 30 weeks. The mastoid cells
develop after birth. The malleus and incus
arise from the first arch cartilage by 8 weeks of
age, and begin to ossify at 4 months. Concurrently, the stapes forms and ossifies from the
second arch cartilage (with the exception of
the medial lamina of the footplate, which is
derived from the otic capsule).9
Microtia occurs as a broad range of deformities, involving to variable degrees the first and
second branchial arches. Failure of development or adverse events that occur early, during
the sixth through eighth weeks of gestation,
are felt to lead to the clinical spectrum of
microtia. Later gestational insults most often
result in less profound expressions of ear deformity. The auricular deformities may be accompanied by facial nerve abnormalities, middle ear maldevelopment, mandibular
hypoplasia, and lip and palatal clefts. The most
common clinical presentation of microtia (approximately 60 to 70 percent) is that of an
isolated deformity.10 Despite absence of other
readily identifiable clinical manifestations,
however, radiographic examination will often
demonstrate pathologic disease in the mandible (most notable in the condyle), temporal
bone, and vertebra of these patients. Isolated
microtia is felt to represent the mildest form of
hemifacial microsomia.11–14
TYPES
OF
MICROTIA
A number of classification systems for microtia have been proposed. Microtic auricular deformities are usually classified according to the
vestigial structures present.13,15–19 Nagata has
proposed a concise categorization of this disorder, directly pertinent to the surgical correction of each deformity. This system defines
lobule-type, concha-type, and small conchatype microtia20 –24 (Fig. 7). Anotia, the most
severe form of microtia, represents the complete absence of the external ear. Those microtic ears with a remnant ear and lobule without the concha, acoustic meatus, and tragus
are categorized as lobule-type microtia. In concha-type microtia, the lobule, concha, acoustic
meatus, tragus, and incisura tragica are present
to variable degrees. Classically, the features of
small concha-type microtia include the remnant ear and lobule with only a small indentation representing the concha. As certain microtia variants exist with a well-developed external
ear save for hypoplasia of the middle third,
FIG. 4. The auricular muscles. Three extrinsic muscles:
anterior (A), superior (S), and posterior (P); and six intrinsic
muscles: helical muscles, large (HL) and small (HS), muscle
of the tragus (T), muscle of the antitragus (AT), transverse
muscle (TM), oblique muscle (O).
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PLASTIC AND RECONSTRUCTIVE SURGERY,
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more pregnancies. This is more pronounced
for anotia than for microtia.25
Microtia has long been felt to represent one
end of the spectrum of hemifacial microsomia.10,13 Although debates in the literature continue, mounting evidence points to the commonality of not only “isolated microtia” and
hemifacial microsomia but also oculoauriculovertebral dysplasia and Goldenhar syndrome,
as variants of the same condition, each exhibiting variable degrees of auricular
malformation.12,13,26
DIAGNOSTIC STUDIES AND EVALUATION
MICROTIA
FIG. 5. Variations in ear position. (Above, left) The aesthetic ideal. (From Tolleth, H. Artistic anatomy, dimensions, and proportions of the external ear. Clin. Plast. Surg. 5:
337, 1978. Used with permission.)
small concha-type microtic ears are probably
best characterized by the presence of a small
concha.
EPIDEMIOLOGY
The cause of microtia is felt to be heterogeneous, including genetic aberrations, teratogens, and vascular abnormalities.10 Excluding
known chromosomal anomalies, large multinational registries of congenital malformations
suggest the prevalence of microtia to be from
0.76 to 2.35 per 10,000 births.10 –13,25 It is generally held that there is a lower incidence of
microtia among whites (and probably blacks)
than in Hispanics and Asians. The proportion
of anotia and microtia also varies between
races, with the lowest proportion of anotia seen
in whites. In unilateral cases, the right side
appears to be more frequently affected than
the left side, especially when the ear malformation occurs as an isolated deformity. There is a
male excess, again most pronounced in isolated forms of microtia. Anotia and microtia
are associated with other congenital malformations, to a comparable degree. Among associated malformations, facial clefts and cardiac
defects are the most common (about 30 percent of these infants are so affected), followed
by anophthalmia or microphthalmia (14 percent), limb reduction defects or severe renal
malformations (11 percent), and holoprosencephaly (7 percent). A maternal parity effect is
also seen, with an increased risk at four or
IN
Initial assessment of patients with microtia
should include a thorough physical examination: evaluation of facial and ear structure, symmetry, and animation, and dental occlusal relationships. A family history and subsequent
genetic study/counseling will address any syndromic issues. A complete audiologic evaluation and radiographic study of the temporal
bones is critical in all patients with microtia.
Classically, it has been held that a small external auditory canal is associated with a mixed
hearing loss, whereas an atretic canal has been
linked primarily to a conductive hearing loss.27
In addition, the presence of a tragus in a microtic ear has been considered an indication of
a functional middle ear.28 A normal middle ear
is rarely found in conjunction with microtia,
but the status of the middle ear is not directly
related to the external deformity. Although the
severity of the external deformity appears to
correlate with the severity of the temporal
bone abnormalities, no such association between the severity of the dysmorphic features
and the degree of hearing loss has been noted.10 It is therefore important to conduct a
FIG. 6. Embryology of the external ear. (Left) Hillock formation in an 11-mm human embryo. (Middle) Hillock configuration in a 15-mm embryo at 6 weeks’ gestation. (Right)
Adult auricle depicting the hillock derivations.
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FIG. 7. Types of microtia. Anotia (above, left); lobular type microtia (above); intermediate deformities having elements of both
lobule and helix (center); isolated tragal element with external auditory meatus (center, right); and deformities having conchal,
tragal, ear canal, lobule, and helical elements (including “cup” ear, “lop ear,” “crumpled ear,” and conchal and small conchal
microtia) (below).
complete radiographic and audiologic evaluation for every child with microtia, regardless
of clinical presentation. It must be remembered that the middle ear is formed later
embryologically than is the external ear.
Thus, although patients with relatively minor
unilateral deformities often hear and speak
well, attempts to correlate function with the
presence or absence of certain anatomic
remnants of the hypoplastic external ear remain unreliable.
Sensorineural, conductive, and mixed
(sensorineural and conductive) hearing loss
may be present in the microtic ear. The predominant hearing deficit in microtia/aural
atresia is conductive hearing loss (80 to 90
percent). However, sensorineural hearing
loss has been found to account for 10 to 15
percent of the hearing loss in these children
and should not be overlooked.10,28,29 To eval-
uate these patients, and before any ear surgery, audiometric studies, including an auditory brainstem response, are performed to
determine the degree of sensorineural and
conductive hearing losses. In the case of an
associated atretic external auditory canal, the
status of the middle ear and the need to rule
out a cholesteatoma are of great concern.
The middle ear deformity may range from
minor ossicular chain disruption (the stapes
is usually normal) to complete loss of the
tympanic cavity. A high-resolution computed
tomographic scan of the temporal bone will
best evaluate the status of the ossicles and
middle ear cleft, providing critical anatomic
information for any proposed otologic surgery.30 Nuclear magnetic resonance imaging
may also be helpful in defining the course of
the facial nerve, which is often displaced in
middle ear malformations.28,29
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CONSIDERATIONS
PLASTIC AND RECONSTRUCTIVE SURGERY,
FOR
OTOLOGIC SURGERY
It is well accepted, and intuitively obvious,
that binaural hearing affords improved sound
localization and speech perception. Tradition
has held that middle ear reconstruction is not
indicated for unilateral microtia with normal
hearing in the contralateral ear. This is based
on the observation that patients with microtia
often fail to achieve true binaural hearing following middle ear surgery because they continue to rely almost exclusively on the normal
ear. This approach is also supported by experimental observations suggesting that the auditory neural structures critical for binaural processing develop only if binaural hearing is
undisturbed early in life.31 As such, the classic
treatment of children with unilateral microtia
has focused primarily on the preservation of
the normal ear, with amplification of the affected one. Conversely, more recent studies
have demonstrated that children with unilateral hearing loss from any cause are at risk for
delayed language development, attention deficit, and poor school performance.32 In addition, the plasticity in the developing auditory
system may be greater than originally suggested, as a number of patients may exhibit
binaural processing, albeit subnormal, even after long-term deprivation.33–35 These considerations have led to an increased interest in middle ear exploration in an attempt to improve
hearing in children with congenital auricular
deformities.
Middle ear surgery, in experienced hands,
results in some hearing improvement in approximately 70 percent of cases. These interventions, although encouraging, entail certain
risks, such as injury to the facial nerve and a
decrease in sensorineural hearing levels.30,36 –38
This potential morbidity suggests that middle
ear surgery should be undertaken only when a
final air-bone gap of 30 dB or better may be
expected.38 Many authorities argue that because of the modest hearing obtained with surgical intervention, the risks do not warrant
surgical intervention. In addition, some degradation of hearing may occur postoperatively,
usually as a result of stenosis of the new external auditory canal. In approximately one-third
of these patients, surgical revision will be required. Although long-term studies are scarce,
in suitable candidates it appears that a speech
reception threshold of 30 dB can be achieved
in greater than two-thirds of patients. The risk
June 2002
of facial nerve injury in experienced hands
approximates that of cholesteatoma surgery
and the risk of sensorineural hearing loss is
comparable to that reported for stapedectomy,
suggesting a favorable risk/benefit ratio for
middle ear exploration in selected
patients.36 –39
The current approach to middle ear surgery
involves careful evaluation of the status of the
ossicles, mastoid, and facial nerve with specific
selection criteria to establish those patients
who will be appropriate candidates for surgical
exploration.32,36 – 40 A rating system suggested by
Aguilar and Jahrsdoerfer assigns a cumulative
point scale to identify those patients who will
benefit from middle ear surgery. In this system,
one point is given for the presence of each of
the following: an open oval window, an adequate middle ear space, a normal facial nerve
course, a malleus-incus complex, adequate
mastoid pneumatization, an incus-stapes connection, good external ear appearance, and
canal stenosis with a malleus bar. Two points
are given for presence of the stapes. A score of
8 or more suggests a good surgical candidate,
with an anticipated success rate of approximately 60 percent. A score of 5 or less contraindicates surgery, as does a predominately sensorineural hearing loss, complete lack of
pneumatization of the mastoid, or obstruction
of the mandibular condyle and/or glenoid
fossa.40
In bilateral microtia, early and conscientious
use of bone-conductive hearing aids is imperative for social hearing and speech development. Traditional dictates have held that if
adequate auditory acuity is not achieved with
the use of hearing aids by approximately 1 year
of age, middle ear exploration on the most
favorable side should be performed.40 However, as previously noted, not all patients are
favorable candidates for surgery. This is especially true in bilateral deformities, which are
often more severe, and carry higher risks for
surgical intervention. If otologic surgery is
deemed appropriate, the anticipated success
rate approximates only 50 percent in bilateral
cases.37,38,41 The hearing deficits in many of
these children are either not treated surgically
or the surgical intervention is delayed until
later in childhood.
Most of the hearing deficits in children with
bilateral microtia are managed primarily with
hearing aids. There have been a number of
advances in conductive hearing devices, but a
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AURICULAR RECONSTRUCTION FOR MICROTIA
major limitation of hearing aids has been their
fixation to the mastoid. Bone aids have been
traditionally applied transcutaneously to intact
skin. The aids are applied with adhesives, headbands, or spectacles, which pose numerous
problems for young children. The small size of
the nose and lack of an external ear provides
little support for spectacles, and adhesives are
difficult to use and may lead to dermatitis or
local skin reactions.32 During the 1980s, boneanchored hearing aids secured with an osseointegrated implant were developed. The implant is usually composed of a ceramic with a
titanium and/or gold core that is compatible
with magnetic resonance imaging. These implants were initially used in adults with discharging ears, but have been studied in children with congenital deformities 2 years of age
and older. The bone-anchored hearing aid has
demonstrated marked improvement over conventional aids in hearing threshold levels, as
well as in aiding previously refractory ears,
likely because of its improved anchorage to the
mastoid. These implants are well tolerated in
children with congenital deformities, with minimal adverse effects, and the success of these
implants has obviated the need for middle ear
exploration in certain cases. These aids have a
functioning and retention rate of over 95 percent on long-term follow-up, with a soft-tissue
reaction rate of about 30 percent (these infections rarely lead to implant removal).42– 48 The
location for securing a conductive hearing aid
must be carefully considered in the planning
of auricular reconstruction to ensure good coaptation and hearing, and avoidance of surgical incision sites. Unfortunately, a purely implantable bone conduction aid, which might
obviate a number of these issues, has remained
largely in the experimental realm, and is not
yet a central part of the clinical strategy.49 –51
If middle ear reconstruction is deemed appropriate, it must be carefully coordinated with
the auricular reconstruction, taking into account canal position, the vascular axis of the
flaps, and location of the incisions used in
external ear reconstruction. This may require
an additional stage in the auricular reconstruction. Flexibility on the part of both the otologist and the plastic surgeon is necessary. Brent,
in his extensive experience, prefers to delay
the middle ear surgery until the auricular reconstruction is completed, and this has been
the standard approach to management in most
patients.52–56 Others have proposed integrated
protocols in which the atresia repair and the
auricular reconstruction are divided into
stages, beginning with initial placement of the
cartilage framework, followed by the atresia
repair in a three- to five-stage procedure.57,58
Both approaches appear to work well. However, for either technique to be successful, a
joint management plan customized to meet
the reconstructive goals of each individual patient is crucial.
HISTORY
OF
AURICULAR RECONSTRUCTION
Early attempts at external ear reconstruction
were rather crude and were primarily directed
toward the reconstruction of partial losses resulting from trauma.59 Because of the paucity
of knowledge on grafting and flap physiology,
and the lack of anesthesia, one can easily surmise that these attempts were fraught with
high complication rates and less-than-ideal results. Nevertheless, as experience with moving
and shaping tissue was gained, legitimate inroads were made. In 1597, Tagliacozzi applied
his now classic pedicled arm flap technique in
the reconstruction of a monk’s ear, and in the
mid 1800s Dieffenbach used a folded mastoid
flap to repair a traumatic ear defect.
Until the mid-twentieth century, total ear
reconstruction for microtia remained an elusive goal and was deemed impossible by most
surgeons. The experimental and clinical use of
autogenous costal cartilage reported by Pierce
and others in the early 1930s ushered in a new
era in reconstruction that could be uniquely
applied to ear reconstruction.60 Most ear reconstructive techniques have been derived
from the formula that uses a framework placed
beneath the skin to create an ear form. Numerous materials have been used to fabricate the
ear framework, but autologous cartilage has
long been considered the standard material.
Modern auricular reconstruction has been
credited to Tanzer, who thoroughly detailed
the principles, techniques, and critical evaluation of total ear reconstruction using carved
autologous costal cartilage.61,62 Borrowing from
these principles, Brent, Nagata, and others
have refined the technique of ear reconstruction to an art form.20 –24,52–56 A history of ear
reconstruction through the mid-twentieth century is nicely chronicled by Converse.59
TIMING
OF
AURICULAR RECONSTRUCTION
The primary factors considered in determining the most appropriate timing for auricular
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PLASTIC AND RECONSTRUCTIVE SURGERY,
reconstruction include the age of external ear
maturity, the availability of adequate donor-site
rib cartilage, and the school age and risk of peer
derision.61 Although ear width will continue to
increase until age 10, it has been established that
85 percent of ear development is attained by 3
years of age.63,64 Rib cartilage is rarely of sufficient
size until the age of 5 to 6 years, which coincides
with the beginning of school. In addition, the
autologous cartilage construct will usually grow at
a rate comparable to the normal ear, and sometimes to a size slightly larger that the native ear.
The cartilage framework is thus carved to match
the dimensions of the opposite normal ear or, in
very young patients, it is made slightly larger.26,62,65 Brent noted that with a minimum 5-year
follow-up, 48 percent of the reconstructed ears
grew at the same rate, 41.6 percent grew several
millimeters larger, and 10.3 percent lagged several millimeters behind the native ear.66 Weighing all these factors, Brent and many others have
recommend performing ear reconstruction between the ages of 4 and 6 years, during preschool, to complete the reconstruction before
the child enters first grade. However, some surgeons, especially those using the Nagata technique, may delay the surgery until a later age.
The recommended age of surgery in Japan is 10
years; a chest circumference (at the level of the
xiphoid) of at least 60 cm is also an acceptable
criterion. This may relate to the relatively large
volume of cartilage needed for reconstruction as
required by the Nagata technique.20 –24,67
CHOICE
OF
AURICULAR FRAMEWORK
There has been continued debate over the
use of autologous versus nonautologous auricular frameworks. Proponents of each of the
different framework materials cite legitimate
reasons for their specific material preferences.
These include the number of operative procedures and donor-site morbidity (more with autologous cartilage constructs), erosion or migration of the implant, and infectious
complications or exposure of the implant
(more with alloplastic constructs).
Autologous costal cartilage is the most commonly used and preferred material for ear reconstruction. It has a demonstrated track
record for durability and stability over time but
is not without shortcomings. Harvest of the
costal cartilage results in a visible anterior
chest-wall deformity in most patients, and although local application of Marcaine into the
harvest site may ameliorate it somewhat, con-
June 2002
siderable pain and discomfort is present in the
initial postoperative period. The cartilage
framework is usually harvested from the synchondrosis of the sixth, seventh, and eighth
ribs. Preservation of perichondrium on the surface of the cartilage may help with construct
adherence to the recipient site and promote
graft viability. The entire perichondrial sleeve
has been elevated with the costal cartilage
graft, but because of problems of significant
chest-wall depression and deformity, most authors prefer to leave at least some remnant of
the perichondrium in situ to support cartilage
regeneration at the harvest site. To satisfy the
needs of both the construct and the chest-wall
donor site, the superficial perichondrium is
usually harvested with the graft, leaving the
posterior perichondrium at the donor
site.52,61,62,68,69 Most authors advocate harvest of
the contralateral cartilage. Fukuda and
Yamada prefer harvesting the ipsilateral cartilage, placing the superficial perichondrium
side down to enhance contact with the mastoid
surface and construct stability.70
Cronin and later Ohmori et al. described use
of the Silastic framework for auricular reconstruction.71–75 The initial aesthetic results were
often excellent, and donor-site deformity was a
nonissue. Long-term follow-up, however, demonstrated spontaneous exposure of the implant
with failure of the reconstruction in many cases.
In addition, minor abrasions or trauma also resulted in exposure and failure. The complications entailed in this technique have prompted
Cronin and Brauer to abandon the use of silicone implants for ear reconstruction.
The use of porous polyethylene has been
recently advocated by Reinisch.76 A total of 116
patients over an 8-year period demonstrated an
initial high complication rate. With technique
modification, however, good short-term (2
years) results were reported. The inertness and
porous quality of porous polyethylene provide
better tissue anchorage, a major advantage
over smooth Silastic implants. The performance of these constructs over time has not
been established, and this technique remains
to be proved safe and reliable.
Elisabeth K. Beahm, M.D.
Department of Plastic Surgery
M. D. Anderson Cancer Center
1515 Holcombe Blvd., Box 443
Houston, Texas 77030
[email protected]
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AURICULAR RECONSTRUCTION FOR MICROTIA
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Self-Assessment Examination follows on
the next page.
Self-Assessment Examination
Auricular Reconstruction for Microtia: Part I
by Elisabeth K. Beahm, M.D., and Robert L. Walton, M.D.
1. SENSIBILITY TO THE EXTERNAL AUDITORY CANAL IS PROVIDED BY WHICH OF THE FOLLOWING
NERVES?
A) Lesser occipital nerve
B) Maxillary division of trigeminal nerve
C) Auriculotemporal nerve
D) Auricular branch of vagus nerve
E) Greater auricular nerve
2. THE CONCHAL VASCULAR NETWORK IS DERIVED PRIMARILY FROM WHICH OF THE FOLLOWING
SOURCES?
A) Subbranch of the upper auricular branch of the superficial temporal artery
B) Occipital artery
C) Perforating branches of the postauricular artery
D) Direct branches of the superficial temporal artery
E) Mastoid artery
3. THE CONCHA AND MEATUS PORTIONS OF THE EXTERNAL EAR PREFERENTIALLY DRAIN TO WHICH OF
THE FOLLOWING LYMPH NODES?
A) Parotid and infraclavicular lymph nodes
B) Superior cervical lymph nodes
C) Postauricular lymph nodes
D) Posterior cervical lymph nodes
E) Submandibular lymph nodes
4. THE TRAGUS IS DERIVED FROM WHICH OF THE FOLLOWING EMBRYONIC PRECURSORS?
A) The hyoid arch
B) The first branchial arch
C) The second branchial arch
D) The first branchial cleft
E) The posterior hillocks
5. WHICH OF THE FOLLOWING STATEMENTS ABOUT MICROTIA IS TRUE?
A) The incidence of microtia varies from 5.20 to 10.55 per 10,000 births.
B) Anotia and microtia are rarely associated with other congenital malformations.
C) There is a female preponderance for microtia.
D) In unilateral microtia, the right side predominates.
E) Limb reduction defects are the most common associated malformations.
6. THE PRESENCE OF WHICH ONE OF THE FOLLOWING EXTERNAL EAR PARTS IS ASSOCIATED WITH A
FUNCTIONAL MIDDLE EAR?
A) Lobule
B) Helix
C) Concha
D) Tragus
E) Antitragus
7. AT WHAT AGE WILL THE EXTERNAL EAR ATTAIN 85 PERCENT OF ITS ADULT SIZE?
A) 2 years
B) 3 years
C) 5 years
D) 8 years
E) 10 years
8. WHICH OF THE FOLLOWING REPRESENTS THE MAJOR SHORTCOMING OF THE SILASTIC FRAMEWORK
FOR AURICULAR RECONSTRUCTION?
A) Migration of the implant
B) Poor definition
C) Cost
D) Exposure
E) Temporal arteritis
To complete the examination for CME credit, turn to page 2626 for instructions and the response form.