OTOLOGY SEMINAR
Ear reconstruction: review and prospects
R3 楊宗霖
2002-02-20
Microtia
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normal external ear anatomy
embryology: 4-8 wks: inner ear; 4-14 wks: external ear
incidence of microtia
- 0.03% (1 in 10000 to 20000)
- half of these patients associated with congenital anomalies
- right ear, boy (2.5x), unilateral (4x): more
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classification: simplified by evaluation external auricle alone
- I mild deformity, with slightly dysmorphic helix and antihelix
as lob ear, cupped ear
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No need of other tissue in reconstruction
II: (atypical microtia) dysplasia: all major structures present to some degree
need additional skin and cartilage
with or without stenosis of external ear canal
III: (classic microtia) dysplasia: few or no recognizable landmarks
lobe is often present with anterior position
Classic microtia reconstruction
Stage I : cartilage implantation
/ place the framework best fit the face symmetry
/ three templates made from the radiological evaluation
- positioning plate: for the contour of the normal ear
- sizing plate: to test the skin pocket where cartilaginous framework is placed
- carving template: landmark or the ear
/ donor: chest site
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use the 6th,7th synchondrosis, expose rib 5-8
rib is harvested with the perichondrium, typically 9 cm in length
the framework and helix were then carved
recipient site: the ear
incision line: anterior-superior margin of the lobe
create a thin flap to cover the cartilage flap
framework is placed in the pocket
insertion silicon drains with vacuum to promote adhesion of non-nourishing flap
Stage II: lobe transfer
/ 2-3 months after stage I procedure
/ a simple transposition flap into the donor site from inferior border of framework
/ the lobe is wrapped around the posterior-inferior margin of framework
Stage III post-auricular skin grafting
/ to create post-auricular sulcus
/ to project the ear away from the surface of the mastoid
/ post-auricular skin over the mastoid is undermined and advanced into
post-auricular sulcus
/ greater projection with placement of a wedge of rib cartilage
turnover the occipitalis fascia from behind the ear
Stage IV tragus reconstruction
/ the aim of the operation is to form a tragus and concha bowl
/ an composite graft is removed form the contra-lateral concha cymba
/ incision is made along the posterior border of future tragus, and the composite flap
is placed in the place to make some projection
/ conchal bowl was debulked of scar and redundant skin tag
/ care for the facial nerve anomalies
Management of the hairline
/ normal hairline is above the apex of the external ear
/ lower hairline is the most common problems
/ management depends on how much was involved
- if only helix: electrolysis & clipping
- if 1/3 or more of the ear: skin graft
- better to eradicate the ear with non-surgical method
- laser: reduce of epidermal appendage, eliminate the apocrine sweat glands
Long-term results
/ Complications
- major is rare
- minor as hematoma or infection may loss the graft
- scar formation and poor contouring improved with time
/ Durability of the constructed auricle
- most ears retain their form in the following years
- no softening or shrinkage of the cartilaginous framework
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some report that reconstructed ear in young patients can be expected to grow
Physiological and emotional benefit
Culture-expanded ear condrocyte transplants
/ A polymer template was formed in the shape of a human auricle
- using a nonwoven mesh of polyglycolic acid (PGA)molded
- then immersed in a 1% solution of polylactic acid.(PLA)
- template was seeded with chondrocytes from bovine articular cartilage
- then implanted into subcutaneous pockets on the dorsa of 10 athymic mice.
/ Specimens harvested 12 weeks after implantation
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Gross morphologic and histologic analysis: new cartilage formation.
The three-dimensional structure was maintained after removal of an external
stent
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The overall geometry of the experimental specimens closely resembled
the complex structure of the child's auricle
/ Both articular and ear sources of chondrocytes have been used in past with success
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suspension of ear chondrocytes injected into a subcutaneous location
biochemical and histological data with greater similarity to those of native
cartilage.
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The subcutaneous environment of native ear cartilage accommodates
subcutaneously injected ear chondrocyte transplants better than aiticular
transplant
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the phenomenon is attributable to the local environment in which
isolated chondrocytes from different sources are introduced.
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Native structural and biochemical cues within the local environment are believed
to guide the proliferation of the differentiated chondrocytes.
/ To construct an autologous cartilage graft, cells must be multiplied in vitro
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Culture cells will lose its phenotypes
Cells were isolated from the ear cartilage, multiplication in mono-layer culture
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Cultured in 10% fetal calf serum, unable to induce re-differentiation.
Some seeded in alginate and cultured for 3 weeks in serum-free medium
with insulin-like growth factor 1 (IGF-1) and transforming growth factor-beta2
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Chondrocytes from the ears of young, but not adult, rabbits, synthesized
significantly more glycosaminoglycan
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Using human ear cells, glycosaminoglycan synthesis could also be stimulated
by replacing serum with insulin-like growth factor and TGF-beta.
/ Autogenous cartilage using alternative polymers
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Previous successful efforts have used an immunocompromised nude mouse
xenograft model
by using polyglycolic acid/polylacic acid (PGA/PLA)
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Less success in an immunocompetent autogenous animal model is due to
inflammatory response.
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alternative polymer material, Pluronic F-127 (polyethylene oxide and
polypropylene oxide).
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Injection of autologous porcine auricular chondrocytes suspended in a
biodegradable, biocompatible hydrogel of Pluronic F-127 resulted in the
formation of cartilage in the approximate size and shape of a human ear helix.
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Final product: cartilage without residual foreign material
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Some other new material as polyethylene, scrylic, extrapurified silasic
success in limited inflammation & cover with pure elastic cartilage
References
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2. Aguilar EF. Auricular reconstruction in congenital anomalies of the ear. Facial
Plast Surg Clin North Am. 2001:9;159-69.
3. Spring PM et al. Congenital aural atresia. J La State Med Soc.1997;149:6-9.
4. Aguilar EF 3rd. Auricular reconstruction of congenital microtia (grade III).
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Matsumoto K, Maeda M, Fujikawa M. Staged, laminated, costal cartilage
framework for ear reconstruction. Clin Plast Surg. 1990;17:273-85.
van Osch GJ, van der Veen SW, Verwoerd-Verhoef HL. In vitro redifferentiation
of culture-expanded rabbit and human auricular chondrocytes for cartilage
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cartilage. Arch Otolaryngol Head Neck Surg. 2000;126:1448-52.
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helix using an injectable hydrogel scaffold. Laryngoscope. 2000;110:1694-7.
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