MICROTIA

1
MICROTIA
With an Emphasis on Reconstructive Options

• Viet Pham, M.D.
• Harold Pine, M.D.
• Raghu Athre, M.D.
• University of Texas Medical Branch
• Department of Otolaryngology
• Grand Rounds Presentation
• January 26, 2010

All images obtained via Google search unless
otherwise specified. All images used without
permission except for those provided by Dr. Athre.
2
Outline

• Anatomy and Development
• Microtia
• Reconstructive Options
• Autogenous cartilage
• Tissue expanders
• Osseo-integrated prosthesis
• Tissue engineering
• Alloplastic implants
• Conclusion

3
Anatomy and DevelopmentEmbryology

• Development begins at 5 weeks gestation
• First branchial cleft
• Dorsal end of first (mandibular) and second
  (hyoid) branchial arches
• Six mesenchymal proliferations (Hillocks of His)
• First arch (hillocks 1-3), second arch
  (hillocks 4-6)
• Tragus (1)
• Helix (2,3)
• Antihelix (4,5)
• Lobule (6)
• Starts on lower neck but ascends with mandible
  development (weeks 8-12), adult location by
  week 20

4
Anatomy and DevelopmentMusculature

• Intrinsic musculature
• Major and minor helixes
• Tragus
• Antitragus
• Transverse
• Oblique

• Extrinsic musculature
• Anterior auricularis
• Superior auricularis
• Posterior auricularis

5
Anatomy and DevelopmentBlood Supply and
Lymphatics
Superficial Temporal Artery
Posterior Auricular Artery

• Arterial
• Superficial temporal
• Posterior auricular
• Occipital
• Venous
• Superficial temporal
• Posterior auricular
• External jugular
• Retromandibular veins
• Lymphatics
• Parotid lymph nodes
• Cervical lymph nodes

Occipital Artery
6
Anatomy and DevelopmentInnervation
Auriculotemporal
Posterior Auricular

• Auricle (facial nerve)
• Temporal branch ? anterior and superior
  auricularis
• Posterior auricular nerve ? posterior
  auricularis
• Sensory
• Anterior
• Auriculotemporal nerve (V3)
• Greater auricular nerve (anterior branch)
• Arnolds nerve (branch of vagus)
• Posterior
• Greater auricular nerve (C3)
• Lesser occipital nerve (C2,C3)

Temporal Branch
Greater Occipital
Lesser Occipital
Greater Auricular
7
Anatomy and DevelopmentNormal External Ear

• Ear development with age
• 66 of adult size at birth
• 85 of adult size at age 3 years
• 95 of adult size at age 6 years
• Normal height 5.5-6.5cm
• Posterior vertical inclination 5-30º
• Vertical angle parallel or within 15º of nasal
  dorsum
• Helical rim protrudes 1.5-2.0cm from mastoid with
  15-20º protrusion angle

(Bailey, 2006)
8
Microtia

• Abnormal development of external ear
• Incidence of 0.76-2.35 per 10,000 births
• Males affected more than females (2.51)
• Higher occurrence in Hispanics, Asians
  (Japanese), and Native Americans (Navajo, Eskimo)
• Increased risk with increasing multiparity (four
  or greater)
• Predilection for the right ear than left
• Family history in less than 15 of cases

9
MicrotiaClassification and Grading

• First classification system by Marx (1926)
• Amended by Jarhsdoerfer and Aguilar (1988)
• Further refined and reaffirmed by Aguilar (1996),
  only auricular malformations
• Additional classification schemes with
  concomitant congenital aural atresia
• Altmann (1955)
• Lapchenko (1967)
• Gil (1969)
• Jarhsdoerfer and Aguilar (1988)

10
MicrotiaClassification and Grading (Marx)
Normal ear

• Grade I
• Slightly smaller auricle
• Mild deformity but can distinguish each part

• Grade II
• 1/2 2/3 of normal size
• Mild deformity but can distinguish each part

• Grade III
• Severe malformation
• Peanut ear

Grade IV (anotia)
11
MicrotiaClassification and Grading (Aguilar)
Normal ear

• Grade I
• Slightly smaller auricle
• Mild deformity but can distinguish each part

• Grade II
• 1/2 2/3 of normal size
• Mild deformity but can distinguish each part

• Grade III
• Severe malformation
• Peanut ear

Grade IV (anotia)
Grade II (deformities present)
Grade III (includes anotia)
Grade I (normal ear)
12
Microtia Considerations

• Limb reduction
• Renal malformation
• Holoprosencephaly

• Association with other congenital abnormalities
• Cleft palate/lip
• Cardiac defects
• Anophthalmia
• Microphthalmia
• Hearing loss (80-90 conductive hearing loss)
• Sensorineural hearing loss in 10-15
• Can delay additional testing to 6-7 months if
  nonmicrotic ear passes newborn hearing screen
• Middle ear abnormalities but no direct relation
• Associated facial nerve dysfunction

13
Microtia Reconstruction

• Reports of first attempts in 1500s
• Folded mastoid flap by Dieffenbach in mid-1800s
  (for traumatic defect)
• Autogenous cartilage by Pierce in 1930s
• Tanzer subcutaneous placement of autologous
  cartilage graft framework (1959)
• Modified by Brent in 1970s
• Cronin silicone rubber implant (Silastic)
  (1966)
• Williams polyethylene implants (Medpor) (1997)

14
Microtia Reconstruction

• Reconstruction typically delayed until 6 years of
  age
• Especially for unilateral cases
• Sufficient autogenous costal cartilage
• Psychological factors (i.e. manage postoperative
  care, school)
• Congenital aural atresia drill-out no earlier
  than 7 years
• Autogenous cartilage is considered gold standard
• Brent technique
• Nagata technique

15
Microtia ReconstructionBrent Technique

• Adapted from Tanzers six-stage procedure (1959),
  four-stage procedure (1971)
• Prefer to perform by 6 years of age
• Approximately 60-70 of cases done between 6-10
  years
• Four-stage procedure (1974)
• Develop auricular framework
• Lobule transposition
• Auricular framework elevation
• Tragus formation
• Any otologic surgery follows after reconstruction

16
Brent TechniqueStage I Fabricate Auricular Frame

• Template of normal ear (if unilateral) or
  parents ear (if bilateral) on X-ray film
• Decrease size of template by a few millimeters to
  accommodate for skin cover thickness
• Harvest costal cartilage from ribs 6-8
  contralateral to microtic ear
• Base formed by synchondrosis of ribs 6 and 7
• Helical rim formed by floating rib 8
• Pieces attached with clear Nylon suture

(Bailey, 2006)
17
Brent TechniqueStage I Fabricate Auricular Frame

• Place framework in subcutaneous pocket at
  posterior and inferior borders of vestige
• Extra cartilage banked with frame work or in
  chest incision
• Two suction drains beneath and near framework
• Left for five days
• Avoid complications related to pressure and
  bolster dressings

(Walton, 2002)
18
Brent TechniqueStage II Transpose Lobule

• Performed several months after Stage I completed
• Inferiorly based rotational flap to receive
  framework

(Bailey, 2006)
(Walton, 2002)
(Shen, 2004)
19
Brent TechniqueStage III Elevate Framework

• Incision a few millimeters from helical rim
• Dissect over the posterior aspect of the capsule
  until desired amount of projection achieved
• Ear position stabilized with banked cartilage
  posteriorly beneath frame in fascial pocket
• Retroauricular scalp advanced, followed by
  split-thickness skin graft

(Walton, 2002)
(Shen, 2004)
20
Brent TechniqueStage IV Construct Tragus

• Composite skin/cartilage graft from anterolateral
  aspect of contralateral (i.e. normal) conchal
  vault
• J-shaped incision along posterior tragal margin
• Composite graft inserted into incision to project
  neotragus and cavitate retrotragal hollow

(Bailey, 2006)
21
Brent TechniqueStage IV Construct Tragus

• Shadow of neotragus imitates external auditory
  canal
• Conchal bowl deepened with subcutaneous tissue
  excavation
• Adjust for frontal symmetry as needed

(Walton, 2002)
22
Brent TechniquePreoperative and Postoperative
(Walton, 2002)
23
Brent TechniquePreoperative and Postoperative
(Thorne, 2001)
24
Brent TechniqueProcedural Modifications

• Laser hair removal of scalp flaps prior to
  reconstruction
• Create tragus with cartilage framework in Stage I
• Floating cartilage creates helix
• Second strut arches around to form antitragus,
  intertragic notch, and tragus
• Tip of strut affixed to helical crus of main
  frame with horizontal mattress suture using clear
  nylon

Horizontal Mattress Nylon Suture
(Walton, 2002)
Second Strut
25
Brent TechniqueCritique

• High number of stages
• Operative morbidity
• Increased cost
• Aesthetic result of tragal reconstruction
• Lack of definition to conchal bowl, intertragic
  notch, and antitragal contour
• Hyperpigmentation of skin grafts to conchal bowl
• Effacement of postauricular sulcus after
  elevating framework results in decreased
  projection
• Caused by contraction of skin grafts
• Minimize with thicker skin grafts (prefer
  full-thickness) or advancing postauricular skin
  to depth of sulcus and grafting only posterior ear

26
Microtia ReconstructionNagata Technique

• Two-stage technique introduced in 1993
• Technical refinements dependent on type of
  microtia
• Lobular
• Small concha
• Conchal
• Anotia
• Low hairline
• Reconstruction begins at age 10 years and at
  least 60cm chest circumference

27
Nagata TechniqueStage I

• Roughly encompasses first three Brent stages
• Rib cartilage framework with tragal component
  housed in subcutaneous pocket
• Lobule transposition
• Framework assembled with fine-gauge wire sutures
• Three floors correspond to three different
  elevations of frame
• Base cymba, cavum conchae
• Second level crus helicis, fossa triangularis,
  scapha
• Top level helix, antihelix, tragus, antitragus

(Walton, 2002)
28
Nagata TechniqueStage I

• Ipsilateral costal cartilage of ribs 6-9
• Base 6th and 7th costal cartilages
• Helix and crus helicis 8th costal cartilage
• Superior and inferior crus and antihelix 9th
  costal cartilage
• Remaining structures carved from residual
  cartilage
• Most, if not all, perichondrium left intact

(Walton, 2002)
29
Nagata TechniqueStage I

• Anterior lobule/tragal incision with removal of
  2mm circular portion of skin
• W-shaped posterior lobule incision
• Increases surface area to cover cartilage
  construct
• Allows lobule transposition
• Flaps undermined and reapproximated to form cup
  of intertragal notch

2mm circular portion of skin
Anterior incision
Posterior W incision
Not elevated and left intact to augment blood
supply to flaps
Cup of intertragal notch
(Walton, 2002)
30
Nagata TechniqueStage I

• Cartilage framework inserted and positioned
• Posterior flap advanced to anterior flap
• Inverted dog-ear formed from 2mm circular skin
  defect creates incisura intertragica
• Reassembling flaps in Z-plasty fashion transposes
  lobule
• Bolsters secured with mattress sutures and left
  in place for 2 weeks

Excessive skin inverted to form pseudoacoustic
meatus
(Walton, 2002)
31
Nagata TechniqueStage II

• Six months after Stage I
• Crescent-shaped piece of costal cartilage
• Harvested from fifth rib
• Wedged into position to elevate framework
• Serves as posterior conchal wall

(Walton, 2002)
32
Nagata TechniqueStage II
Occipital scalp harvest site

• Temporoparietal fascial flap
• Raised through new scalp incision
• Tunneled subcutaneously to cover
• Posterior aspect of cartilage graft
• Reconstructed auricle
• Mastoid surface
• Retroauricular skin advanced followed by
  split-thickness skin graft
• Ultra-delicate
• Freehand harvest from occipital scalp

(Walton, 2002)
Temporoparietal fascial flap origin
33
Nagata TechniquePreoperative and Postoperative
Stage I Completed
(Walton, 2002)
34
Nagata TechniquePreoperative and Postoperative
Stage II Completed
(Walton, 2002)
35
Nagata TechniqueCritique

• Provides a deeper and more natural conchal bowl
  (no need to excavate subcutaneous tissue)
• High rate of peri-lobular flap necrosis (14)
  from vascular compromise
• More cartilage harvested
• Significant anterior chest wall deformity
• Thicker ears
• High extrusion rate of cartilage framework from
  wire sutures (8)
• Frontal symmetry not addressed, would require
  third stage

36
Autogenous Cartilage GraftRisks and Benefits

• Advantages
• Native tissue
• Less infection
• Potential for 5 growth with time

• Disadvantages
• Cartilage may warp or resorb with time
• Framework extrusion with skin flap necrosis
• Cartilage donor effects
• Pneumothorax
• Atelectasis
• Chest wall deformity/scarring
• Low hairline
• Aesthetics
• Thicker skin with less contour
• Inflammation/infection

37
Other Reconstructive Options

• Single-stage reconstruction
• Tissue expanders
• Osseo-integrated prosthesis
• Tissue engineering
• Alloplastic implant
• Silastic
• Medpor

38
Other Reconstructive OptionsSingle-Stage
Reconstruction

• Used predominantly for partial defects (i.e.
  superior helix or lobule)
• Total ear reconstruction usually entails
• Skin flaps
• Fascial flaps
• External stents
• Results not comparable to multiple-staged
  procedures
• Two-flap, single-stage procedure has been
  converted to a three-stage one (Park, 1997 and
  2000)

39
Other Reconstructive OptionsTissue Expanders

• Hata and Umeda (2000)
• Reconstruct auricle in single stage without skin
  graft
• Good skin texture and match
• Skin innervation preserved
• Park (2000)
• First Stage
• Expand skin and fascial layers
• Cartilage framework sandwiched between both
  layers
• Skin graft over fascial layer
• Second Stage
• Remove cartilage and shape structures from
  framework
• May need skin graft to posterior surface of frame

(Yang, 2009)
40
Other Reconstructive OptionsTissue Expanders

• Pain
• Not well tolerated in young children
• Insertion of expander is a procedure number of
  stages not truly reduced
• Fibrous capsule formation around expander may
  marginalize contouring results

(Yang, 2009)
41
Other Reconstructive OptionsOsseo-Integrated
Prosthesis

• At least 3mm of bone to secure implant
• Indications for use
• Severe soft-tissue or skeletal hypoplasia
• Poor local tissue
• Cancer
• Radiation
• Failed autogenous reconstruction
• High operative risk factors
• Prosthesis changes
• Approximately 2-5 years with ultraviolet
  degradation
• Multiple prosthesis for seasonal skin tones

(Tollefson, 2006)
42
Other Reconstructive OptionsOsseo-Integrated
Prosthesis

• Advantages
• Single, less involved procedure
• Best cosmetic outcome
• No resorption
• Minimal infection
• Inflammation around anchoring pins
• Mechanical trauma to pins
• Tissue overgrowth

• Disadvantages
• Repeat procedures (2,000-7000 per prosthesis)
• Mr. Potato Head social stigma (i.e. if ear
  falls off)
• Precludes future autogenous reconstruction

43
Other Reconstructive OptionsTissue Engineering

• Potential to offer autogenous cartilage without
  morbidity from rib harvest
• Prefabricated framework
• Taut pressure from overlying skin can deform
  frame
• Firm alloplastic frames can withstand pressure
  but extrude
• Difficult to match size and shape of normal ear
• Requires replication of numerous human
  chondrocytes to create adequate framework
• Cao et al (1997)
• Bovine chondrocytes grown in vitro transplanted
  onto synthetic ear-shaped biodegradable scaffold
• Scaffold implanted into immunocompetent mouse
• New cartilage formation with human ear shape
  after 12 weeks

44
Other Reconstructive OptionsTissue Engineering

• Human-sized auricle with hydrogel scaffold in
  pigs (Kamil, 2004)
• Grow chondrocytes on perforated pure gold ear
  mold (Kamil, 2004)
• Harvest chondrocytes from microtic human ears in
  mouse model (Kamil, 2004)

45
Other Reconstructive OptionsSilastic Alloplastic
Implant

• Silicone implant investigated by Cronin (1966)
  and Ohmori (1978)
• Promising results initially
• Disappointing long-term outcomes
• Implant extrusion/resorption secondary to skin
  flap erosion/necrosis
• Minor trauma or abrasions can cause implant
  failure
• May occur years after operation
• Salvage can be done with local skin and
  fascial flaps
• Use has since been abandoned

46
Other Reconstructive OptionsMedpor Alloplastic
Implant

• Prefabricated porous polyethylene auricular
  implant
• Excellent biocompatibility, stability, tissue
  integration, and resistance to infection
• Minimal tissue reaction
• Pore size 150µm allows soft-tissue ingrowth
  improves stability
• Can be bent when heated to 82-100ºC, carved to
  shape, or affixed to other pieces with cautery
• Lobule transposition can be
  performed after three months
• Bone-anchored hearing aid can be placed
  concurrently (Romo, 2006 and 2009)

47
Other Reconstructive OptionsMedpor Alloplastic
Implant

• Less extrusion rates compared to silicone with
  use of temporoparietal fascial (TPF) flap to
  cover framework
• Lower 2/3 inserted in to skin pocket
• Upper portion covered with TPF and skin graft
• Flap must be water-tight
• Soft tissue flaps to treat early implant exposure
  from flap ischemia
• If exposure is less than 1cm
• If tissue integration is seen
• Good short-term results (2-year) but
  long-term results still lacking

TPF Flap
Medpor Implant
(Tollefson, 2006)
48
Other Reconstructive OptionsMedpor Alloplastic
Implant

• Dr. John Reinischs Five Main Advantages
• Good projection and definition
• Decreased reconstruction time
• No scarring from costal cartilage harvest
• Can perform in younger children (3-4 years)
• Shorter learning curve than autogenous cartilage
  graft

49
Other Reconstructive OptionsMedpor Alloplastic
Implant

• Advantages
• Improved cosmetic result compared to autogenous
  cartilage graft
• No resorption
• Low extrusion rate

• Disadvantages
• Not native tissue
• Infection risk with any cut
• Sensitive to trauma and direct contact

TPF Flap
Full-thickness skin graft over top 1/3 of Medpor
Y-shaped incision
Small vacuum drain
(Romo, 2009)
50
Medpor Alloplastic ImplantFirst Stage
Reconstruction

• Scalp incisions
• Made to avoid junctions over arteries
• Perpendicular to direction of hair growth

Subcutaneous pedicle for blood supply to skin
over future conchal bowl
Template marked for implant position
Superficial temporal arteries identified with
Doppler
Long and wide TPF flap is needed to cover the
entire implant
(Reinish, 1998)
51
Medpor Alloplastic ImplantFirst Stage
Reconstruction
Skin exposure flaps over fascia reapproximated to
protect tissue
Lobule mobilized and opened to fit over implant
rim
Postauricular skin harvested from contralateral
ear
(Reinish, 1998)
52
Medpor Alloplastic ImplantFirst Stage
Reconstruction
Abdominal skin graft to cover harvest site
Antibiotic-covered bolster to cover the graft site
(Reinish, 1998)
53
Medpor Alloplastic ImplantFirst Stage
Reconstruction

• Medpor pieces soaked in betadine
• Placed inside 60mL syringe
• Betadine suctioned against finger to drive
  betadine into pores

(Reinish, 1998)
54
Medpor Alloplastic ImplantFirst Stage
Reconstruction
Medpor pieces affixed with electrocautery or
non-absorbable suture
TPF flap lifted with enough to cover the entire
implant
(Reinish, 1998)
55
Medpor Alloplastic ImplantFirst Stage
Reconstruction
TPF flap draped over implant
Two drains, one placed right under implant

• TPF flap must be watertight
• Skin flap will press against TPF and implant if
  truly tight

(Reinish, 1998)
56
Medpor Alloplastic ImplantFirst Stage
Reconstruction
Contralateral postauricular skin flap placed
anteriorly
Trim flaps as needed to keep abdominal flap
behind helical rim
Abdominal skin flap placed posteriorly
(Reinish, 1998)
57
Medpor Alloplastic ImplantSecond Stage
Reconstruction
Excess tissue removed
Anteriorly based flap made near tragus
(Reinish, 1998)
58
Medpor Alloplastic ImplantSecond Stage
Reconstruction
Part of parotid gland removed to make room for
conchal bowl
Anterior flap sutured over itself to make tragus
(Reinish, 1998)
59
Medpor Alloplastic ImplantPreoperative
(Courtesy of Dr. Athre)
60
Medpor Alloplastic ImplantIntraoperative
(Courtesy of Dr. Athre)
61
Medpor Alloplastic ImplantPostoperative
(Courtesy of Dr. Athre)
62
Conclusion

• Microtia can be associated with other congenital
  abnormalities and adverse psychosocial effects
• Surgical intervention can be delayed until the
  child is older
• Reconstruction with autogenous cartilage graft is
  the gold standard
• Alloplastic implants provide improved cosmetic
  results with less staged procedures

(http//www.smbc-comics.com)
63
References

• Altmann F. Congenital atresia of the ear in men
  and animals. Ann Otol Rhinol Laryngol 1955
  64(3)82458.
• Aguilar EA III. Auricular reconstruction of
  congenital microtia (grade III). Laryngoscope
  1996 106(suppl 82)126.
• Aguilar EA III, Jahrsdoerfer RA. The surgical
  repair of congenital microtia and atresia. Arch
  Otolaryngol Head Neck Surg 1988 98600.
• Bailey BJ, Johnson, JT, Newlands SD. Head and
  Neck Surgery Otolaryngology, Fourth Edition.
  Philadelphia Lippincott 20062685-700.
• Brent B. Microtia repair with rib cartilage
  grafts a review of personal experience with 1000
  cases. Clin Plast Surg 2002, 29257271.
• Brent B. The team approach to treating the
  microtia atresia patient. Otolaryngol Clin North
  Am 2000 33(6)135365.
• CaoY, Vacanti JP, Paige KT, et al.
  Transplantation of chondrocytes utilizing a
  polymer-cell construct to produce
  tissue-engineered cartilage in the shape of a
  human ear. Plast Reconstr Surg 1997, 100297302.
• Cronin TD. Use of a Silastic frame for total and
  subtotal reconstruction of the external ear
  preliminary report. Plast Reconstr Surg,
  196637399.
• Cummings CW, Flint PW, Harker LA, et al, editors.
  Otolaryngology head and neck surgery, Fourth
  Edition. Philadelphia Mosby 200444228,
  4439-44.
• Gill NW. Congenital atresia of the ear. A review
  of the surgical findings in 83 cases. J Laryngol
  Otol 1969 8355187.
• Harris J, Kallen B, Robert E. The epidemiology of
  anotia and microtia. JMed Genet 1996 3380913.
• Hata Y Do not forget the merits of microtia
  repair using a tissue expander. Plast Reconstr
  Surg 2002, 109819822.
• Hata Y, Umeda T. Reconstruction of congenital
  microtia by using a tissue expander. JMed Dent
  Sci 2000 4710516.
• Kamil SH, Vancanti MP, Aminuddin BS, et al.
  Tissue engineering of a human sized and shaped
  auricle using a mold. Laryngoscope 2004
  114(5)86770.
• Kamil SH, Vacanti MP, Vacanti CA, Eavey RD.
  Microtia chondrocytes as a donor source for
  tissue-engineered cartilage. Laryngoscope 2004
  11421872190.
• Lapchenko S. On surgery for improving hearing in
  congenital atresia of the external and middle
  ear. Vestn Otorinolaringol 1967 29(2)914.
• Lee KJ. Essentials of Otolaryngology, Fifth
  Edition. McGraw-Hill 2003.
• Nelson SM, Berry RI. Ear disease and hearing loss
  among Navajo childrena mass survey. Laryngoscope
  1984 94(3)31623.
• Ohmori S. Reconstruction of microtia using the
  Silastic frame. Clin Plast Surg 1978
  5(3)37987.

64
References

• Shen, J. Microtia Reconstruction. UTMB Department
  of Otolaryngology Grand Rounds, 2004.
  http//www.utmb.edu/otoref/Grnds/Microtia-Recon-04
  10/Microtia-Recon-slides-0410.pdf ltAccessed
  January 2010gt.
• Shen, J. Microtia Reconstruction. UTMB Department
  of Otolaryngology Grand Rounds, 2004.
  http//www.utmb.edu/otoref/Grnds/Microtia-Recon-04
  10/Microtia-Recon-0410.htm ltAccessed January
  2010gt.
• Tanner PB, Mobley SR. External auricular and
  facial prosthetics a collaborative effort of the
  reconstructive surgeon and anaplastologist.
  Facial Plast Surg Clin North Am 2006 14137145.
• Tanzer RC. Total reconstruction of the external
  ear. Plast Reconstr Surg 1959231.
• Tanzer RC. Total reconstruction of the auricle
  The evolution of a plan of treatment. Plast
  Reconstr Surg 1971 47523.
• Tanzer R, Edgerton M, et al. Symposium on
  Reconstruction of the Auricle, Volume 10. St.
  Louis CV Mosby 19743-11, 46-57.
• Thorne CH, Lawrence EB, Bradley JP, Levine, JP,
  Hammerschlag P, Longaker MT. Auricular
  reconstruction indications for autogenous and
  prosthetic techniques.. Plast Reconstr Surg 2001
  1071241-51.
• Walton RL, Beahm EK. Auricular reconstruction for
  microtia part I. Anatomy, embryology, and
  clinical evaluation. Plast Reconstr Surg 2002
  109(7)247382.
• Williams JD, Romo T III, Sclafani AP, et al.
  Polyethylene implants in auricular
  reconstruction. Arch Otol Head Neck Surg 1997
  123578583.
• Yang SL, Zheng JH, Ding Z, Liu QY, Mao GY, Jin
  YP. Combined fascial flap and expanded skin flap
  for enveloping Medpor framework in microtia
  reconstruction. Aesth Plast Surg 2009 33518-22.
• Zim SA. Microtia reconstruction, an update. Curr
  Opin Otolaryngol Head Neck Surg 2003
  11(4)27581.