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journal homepage: www.JournalofSurgicalResearch.com

Fabrication of three-dimensional scan-to-print earmodel for microtia reconstruction

Byoungjun Jeon, BS,a Chiwon Lee, PhD,b Myungjoon Kim, BS,a

Tae Hyun Choi, MD, PhD,c,* Sungwan Kim, PhD,b,d,**and Sukwha Kim, MD, PhDc

a Interdisciplinary Program for Bioengineering, Seoul National University, Seoul, Koreab Institute of Medical and Biological Engineering, Seoul National University, Seoul, KoreacDepartment of Plastic and Reconstructive Surgery, Institute of Human Environment Interface Biology, College

of Medicine, Seoul National University, Seoul, KoreadDepartment of Biomedical Engineering, College of Medicine, Seoul National University, Seoul, Korea

a r t i c l e i n f o

Article history:

Received 30 December 2015

Received in revised form

1 July 2016

Accepted 2 August 2016

Available online 9 August 2016

Keywords:

Microtia

Reconstruction

3D

Print

Scan

Ear

* Corresponding author. Department of Plastro, Jongno-gu, Seoul 03080 Korea. Tel.: 82-2-** Corresponding author. Department of Biomgu, Seoul 03080, Korea. Tel.: 82-2-2072-3126;

E-mail addresses: psthchoi@snu.ac.kr (T.0022-4804/$ e see front matter ª 2016 Elsevhttp://dx.doi.org/10.1016/j.jss.2016.08.004

a b s t r a c t

Background: Microtia is a congenital deformity of the external ear that occurs in 1 of every

5000 births. Microtia reconstruction using traditional two-dimensional templates does not

provide highly detailed ear shapes. Here, we describe the feasibility of using a three-

dimensional (3D) ear model as a reference.

Materials and methods: Seven children aged from 11 to 16 (6 grade III and 1 grade II microtia)

were recruited from Seoul National University Children’s Hospital, Korea. We generated

3Decomputer-aided design models of each patient’s ear by performing 3D laser scanning

for a mirror-transformed cast of their normal ear. The 3D-printed ear model was used in

microtia reconstruction surgery following the Nagata technique, and its shape was

compared with the casted ear model.

Results: One patient experienced irritation caused by accidently pouring resin into the

external auditory meatus, and another had minor skin necrosis; both complications were

successfully treated. The average percentage differences of the superior, inferior, anterior,

posterior, and lateral views between the casted and 3D-printed ear models were 1.17%,

1.48%, 1.64%, 1.80%, and 5.44%, respectively (average: 2.31%), where the difference between

the casted ear models and traditional two-dimensional templates were 16.03% in average.

Conclusions: Our results show that simple microtia reconstruction can be performed using

3D ear models. The 3D-printed ear models of each patient were consistent and accurately

represented the thickness, depth, and height of the normal ear. The availability of the 3D-

printed ear model in the operating room reduced the amount of unnecessary work during

surgery.

ª 2016 Elsevier Inc. All rights reserved.

ic and Reconstructive Surgery, College of Medicine, Seoul National University, 101 Daehak-2072-1978; fax: 82-2-766-5829.edical Engineering, College of Medicine, Seoul National University, 101 Daehak-ro, Jongno-fax: 82-2-745-7870.H. Choi), sungwan@snu.ac.kr (S. Kim).ier Inc. All rights reserved.

j e o n e t a l � f a b r i c a t i o n o f 3 d s c an - t o - p r i n t e a r m od e l 491

Introduction the carved cartilage and patient’s normal ear, surgeons have

Microtia is a congenital external ear deformity that occurs in

about 1 of every 5000 births.1 Most cases are unilateral but

approximately 10% of deformities affect both external ears.2

Microtia and associated syndromes, for e.g., facial cleft, facial

asymmetry, renal abnormalities, cardiac defects, micro-

phthalmia, polydactyly, or vertebral anomalies, can decrease

patients’ quality of life mainly due to their low self-esteem.3,4

Kristiansen et al. found the desire to have identical ears,

perceiving their ear to look strange, frequent comments and/or

questions from other, the wish to wear sunglasses, and getting

teased to be motivational factors for surgery.5,6 Also, there are

reports that after ear reconstruction 91% of children reported

improvements in self-confidence and that auricular recon-

struction using autologous cartilage in children resulted in sig-

nificant improvements in health-related quality of life.7,8

Moreover, the success of microtia reconstruction is related to

psychological postsurgical recovery of the patient.9 Therefore,

microtia reconstructive surgery is desirable to reshape the ear

deformityandreducebothphysicalandpsychologicalproblems.

Generalmicrotia reconstruction techniques involve the use

of autologous costal cartilage, porous polyethylene (e.g., Med-

por), and ear prostheses.10-12 Prosthetic reconstruction has a

high success rate and good patient satisfaction, but its main

drawback is that prostheses are not autologous tissue and

therefore require ongoing expenses formaintenance visits and

prosthesis replacement every 2-5 y.10,13-15 One problem with

implant reconstruction using porous polyethylene (e.g., Med-

por) is that it is a foreign body framework and sometimes re-

quires secondary surgery for soft-tissue necrosis, as reported

by Baluch et al.10; in addition, it is a ready-made product that

cannot replicate the patient’s unique ear shape. Although

theseprocesses simplify ear reconstruction, thedisadvantages

stated above and a lack of training for newer surgical tech-

niques mean that the most preferred method of microtia

reconstruction among plastic surgeons is staged microtia

repair using autologous costal cartilage.10-12

Microtia reconstructive surgery using autologous costal

cartilage is the most demanding surgical approach.10-12 The

surgery includes harvesting a section or piece of the patient’s

rib cartilage and sculpting it into a newly shaped framework to

repair the ear deformity.10 Two to three surgeries are usually

performed over 12-24 months, depending on the patient’s

condition.10 Before harvesting the rib cartilage, surgeons copy

the shape of the normal ear onto a two-dimensional (2D)

transparent film by placing the film against the normal ear

and tracing its anatomic landmarks.16 After harvesting the rib

cartilage, surgeons use the film to guide sculpting.12,17 When

carving the rib cartilage, surgeons experience some difficulties

mimicking the three-dimensional (3D) ear shape because

traditional microtia reconstructive surgery uses a 2D plane

pattern although the ear is a 3D structure.17,18 Although the

transparency of the film can project the mirror image of the

normal ear and help surgeons sculpt the rib cartilage, it does

not represent the unique 3D information of each patient, such

as the height or thickness of the concha, helix, and antihelix.

As a result, surgeons must keep checking and comparing the

newly shaped framework with the normal ear. To compare

to bring the cartilage from the work station, which is located

distant from the anesthetic patient’s bed, and turn patient’s

head. During this additional step, operation time can be

extended, and it also carries a slight risk of infection. To

overcome these problems associated with this demanding ear

reconstruction technique, 3D technologies are used.

The increase in 3D scanning and printing technologies has

facilitated their use in microtia reconstructive surgery to help

visualize the ear shape and sculpt the rib cartilage. A 3D

template can be produced by scanning the normal ear cast,

making a mirror image of the cast using computer-aided

design (CAD) and printing out a 3D ear model for microtia

reconstruction. This can result in more streamlined surgery

and better outcome. In addition, the 3D-printed ear model can

be shown to a patient and modified if necessary.

In the present study, we evaluated whether the use of 3D

scan-to-print technique can provide detailed 3D information

of the affected ear and enhance surgeon’s intuition for ear

cartilage framework by providing more objective 3D features

when compared with the traditional 2D template-based ear

reconstruction surgery.

Material and methods

Patients

A total of seven children (four females and three males) aged

from 11 to 16, with six children grade III microtia and one child

grade II microtia, were recruited from Seoul National Univer-

sity Children’s Hospital in Seoul, Korea. To cast an ear model

for patients, the institutional approval was obtained by the

Institutional Review Board (IRB) of the Seoul National Uni-

versity College of Medicine and/or Seoul National University

Hospital (IRB no. 1505-081-673). Every patient and their par-

ents were told about the casting process with the possible

risks and the benefits of how the casted ear model would be

used for their microtia reconstructive surgery. After given

them a detailed information about intervention, permission

from both patients and their parents were obtained by signing

the informed consent. Casting of the patients’ normal ears

(four right and three left ears) was performed preoperatively,

and all the ear reconstruction surgeries were performed.

Normal ear molding and casting

Normal ear molds were created instead of direct scanning

because the childrenwere too young to stay still during the 3D

scanning process. Cotton plugs were used to protect the

external auditory meatus. Surgical tape (Micropore, 3M) was

used to cover the hairline around the normal ear to protect it

from the alginate impression material. A 6 � 8 � 6-cm acryl

frame with an open top and bottom was prepared to cast the

patient’s normal ear (Fig. 1).

Alginate impression material (Aroma fine plus 1 kg, GC

Corporation, Japan) was mixed with tap water (8.4 g/20 mL) at

room temperature for 20-30 s to create a mold of the normal

ear. The mixed alginate was poured slowly into the acryl

Fig. 1 e Molding and casting of patient’s normal ear. The process of molding and casting of each patients’ normal ear. (Color

version of figure is available online.)

492 j o u rn a l o f s u r g i c a l r e s e a r c h � d e c em b e r 2 0 1 6 ( 2 0 6 ) 4 9 0e4 9 7

frame until the ear was covered with it. After 30-60 s, the acryl

frame and the mold were separated from the patient’s ear

while keeping the frame and the mold in contact. The mold

was pushed inward (toward the top of the frame) to make

room for the casting material.

A dental stone (Neo plum stone 1 kg, Mutsumi, Japan)

mixed with tap water (100 g/24 mL) was filled in the frame

containing the mold to fabricate a cast of the patient’s normal

ear. Before filling the frame, less concentrated dental stone

mixture was poured into the frame to prevent air bubbles

from forming on the cast’s surface. After 2-3 h of drying, the

mold and cast were separated from the frame. The mold was

discarded, and the cast was used as the final material for 3D

scanning.

3D scanning and printing

Three-dimensional scanning was performed with a NextEn-

gine 3D laser scanner (3D Scanner HD, NextEngine) that gen-

erates an object’s 3D CAD model by capturing and registering

2D images and depth information based on the built-in image

and laser sensors, respectively. The3DCADmodel is generated

by applying the 3D scanner to the cast of the patient’s normal

ear.Toensuresufficient resolutionof the3DCADmodel, the2D

images and corresponding depth information of the cast were

collected using an interval of 30�. After generating the 3D CAD

model,mirror transformationwas used to produce the 3DCAD

model of the patient’s affected ear. For this purpose, we used

the open source software MeshLab to process and edit the 3D

model. Once the 3D model of the patient’s affected ear was

obtained, we were able to print the model using a 3D printer

(Edison, Rokit, Korea) at a resolution of 0.05 mm (Fig. 2).

Microtia reconstruction

Microtia reconstructive surgery was performed following the

Nagata technique.10,12,16,17 After harvesting the patient’s rib

cartilage, sculpting was performed using the 3D-printed ear

model as a reference to fabricate a framework for microtia

reconstruction (Fig. 3).

Evaluating 3D-printed ear model accuracy

To evaluate the percentage differences between the casted

normal ear and 3D-printed ear model, a GNU image manipula-

tion program (GIMP, The GIMP Team) was used to mirror

transform one of the models. Next, the open source code of

Mathematica was used to determine the percentage differ-

ences, and the merged images were collected and created. A

digital camera was used to capture the five sides (superior,

inferior, anterior, posterior, and lateral views)of eachcastedear

and 3D-printedmodel (Fig. 4 shows the lateral view). The black

portionof themerged images shows thedifferencebetween the

casted and 3Dmodels. As a reference, lateral viewof traditional

2D template consisting of x and y axis only was comparedwith

casted ear model due to the absence of z axis in 2D coordinate.

Results

Patients and postoperative follow-up

The mean patient age was 13. Casts of each of the seven pa-

tients’ normal ears were produced. All the surgical procedures

included a 3D-printed model as a reference of the affected

Fig. 2 e Affected side 3D ear model manufacturing process. After 3D scanning the cast, scanned image was reconstructed.

The reconstructed image was thenmirror transformed to generate 3Dmodel of patient’s affected side ear. The generated 3D

ear model was 3D printed. (Color version of figure is available online.)

j e o n e t a l � f a b r i c a t i o n o f 3 d s c an - t o - p r i n t e a r m od e l 493

side. Although patientsmight have felt some discomfortwhen

the resin was applied to their normal ear to create the mold,

none of them had any problems (e.g., contact dermatitis or

allergic reaction) from applying the alginate mixture, except

for one case of irritation caused by accidently pouring a small

amount of mixed alginate into the external auditory meatus.

To minimize irritation, ear-nose-throat forceps were used to

remove the solidified alginate inside the external auditory

meatus. One patient also experienced minimal skin necrosis

on the antihelix after microtia reconstruction, so we treated

the necrosis by secondary intention. The other five patients

did not have any complications.

Fig. 3 e Sculpting the harvested rib cartilage using 3D earmodel and before and/or after microtia reconstruction. The process

of sculpting the harvested rib cartilage for mirotia reconstruction relying on 3D ear model and presurgery and/or

postsurgery of the patient. (Color version of figure is available online.)

494 j o u rn a l o f s u r g i c a l r e s e a r c h � d e c em b e r 2 0 1 6 ( 2 0 6 ) 4 9 0e4 9 7

Percentage differences between casted ear and 3D-printedear model

Unlike 2D templates, the 3D printing outcomes of each patient

were fairly consistent and accurate, representing normal ear

symmetry (Fig. 4 and Table 1). The average percentage dif-

ferences of the superior, inferior, anterior, posterior, and

lateral views were 1.17%, 1.48%, 1.64%, 1.80%, and 5.44%,

respectively, for an average 2.31% difference between the

casted ear and 3D-printed ear models (Table 1).

Two-dimensional template and 3D ear model comparison

Traditional 2Dtemplateandcastedearmodel comparisongives

different results as expected. Since there is no z-component in

2Dcoordinatesystem,percentagedifferencesof the lateralview

were the only possible outcome which was 16.03% (Table 2).

Traditional 2D templates do not provide height information,

which means that surgeons must continually check the pa-

tient’snormalearwhilecarvingtheribcartilage.Whenusing3D

ear model, however, surgeons do not need to keep track of the

ear shape toacquireheight informationduringsculpting (Fig. 3).

Using a 3D ear model, it reduces unnecessary work during

surgery. Compared to the 2D template, the 3D-printed ear

model was a useful reference for visualizing the ear scaffold

while sculpting valuable rib cartilage (Fig. 3).

Discussion

Major difficulty in microtia reconstruction is creating a 3D

cartilage framework out of costal cartilage. There are several

options for practicing cartilage framework designing sug-

gested by Brent, Chen, Yamada et alwhich are summarized in

Thadani’s article.19 However, practicing variousmethodswith

2D template is still time-consuming for surgeon to locate parts

of 3D ear in costal cartilage. Themain issue is that the current

surgical rehearsal or method for microtia reconstruction is to

use 2D template when using harvested rib cartilage.10,12,16,17

This reference tool lacks the necessary information for

reconstruction because it does not exactly represent the

height, depth features, and mirror-imaged ear.

We used the promising methods of 3D scanning and

printing to provide more detailed information for recon-

struction.20-23 First, we tried to directly scan the patient’s

normal ear with the 3D scanner. However, our patients were

Fig. 4 e Difference in shape between the casted ear model and 3D-printed ear model. Black portion of the merged image

indicates the percentage difference between the casted ear model and 3D-printed ear model. (Color version of figure is

available online.)

j e o n e t a l � f a b r i c a t i o n o f 3 d s c an - t o - p r i n t e a r m od e l 495

too young to sit through the process, resulting in a low-quality

3D scanned image. To overcome the limitation, we created a

mold of the normal ear and casted an ear model for 3D

scanning (Fig. 1). There was no vibration or any other problem

with scanning using the stationary casted model, which

enabled us to rescan the model and reproduce a better, high-

resolution 3D image. It also made it possible for the 3D scan-

ner to obtain the information needed for mirror transforming

and 3D printing. If faster 3D scanners were available other

than the various types summarized by Murphy and Atala,21 it

would have reduced the time needed to scan the casted

model, making it possible to directly scan the patient’s ear.

The difference between the casted and 3D-printed ear

models was only 2.31% (Table 1). In other words, 3D ear

models were similar to the actual ear, regarding that the

casted ear model is not different from the actual ear. This

discrepancy may have been caused by our 3D scanner, which

is not the best one available on the market. Still, the 3D-

printed ear model looked exactly like the cast to the naked

eye, except for the fact that it wasmirror-imaged to be used as

a reference tool during ear deformity reconstruction. A 2D

model does not provide every unique detail of each patient’s

ear, such as thickness, depth, or height information of the

concha, helix, and antihelix. Conversely, the 3D model pro-

vided the information surgeons needed to sculpt the har-

vested rib cartilage (Figs. 3 and 4). Although the time to

fabricate 3D-printed ear models is much longer than needed

to trace anatomic landmarks on 2D film, this was not

Table 1 e Difference between the casted ear model and 3D-printed ear model.

Superior Inferior Anterior Posterior Lateral

Patient 1 0.66 0.52 0.97 0.68 1.88

Patient 2 1.51 0.97 1.34 2.69 1.91

Patient 3 0.85 1.63 1.39 1.68 5.15

Patient 4 0.75 0.89 1.34 1.30 7.22

Patient 5 0.71 1.04 0.74 1.00 6.31

Patient 6 1.61 0.92 1.10 1.62 4.34

Patient 7 2.11 4.38 4.63 3.65 11.28

Average 1.17 1.48 1.64 1.80 5.44

Standard deviation 0.57 1.32 1.34 1.03 3.28

Total average percentage difference ¼ 2.31%

Percentage difference between the superior, inferior, anterior, posterior, and lateral view of casted ear model and 3D-printed ear model.

496 j o u rn a l o f s u r g i c a l r e s e a r c h � d e c em b e r 2 0 1 6 ( 2 0 6 ) 4 9 0e4 9 7

problematic because 3D model preparation occurred before

the day of surgery.

Another probable benefit of using the 3D model was the

reduction in the amount of work during surgery. Carving rib

cartilage usually takes place on a separately prepared table

next to an anesthetized patient.12,18 Surgeons have to keep

checking the normal ear when using the 2D template to guide

rib cartilage sculpting. This involves turning the patient’s

head and moving between the sculpting and patient tables.

The final results of microtia reconstruction are often

evaluated by photogrammetry, but this was not possible in

our study because secondary surgery is needed to complete

the reconstruction (e.g., elevation and tragus reconstruction)

which is required for skin to be completely and stably

attached to framework for the actual ear shape to appear, and

skin stabilization takes at least 6 mo after the first surgery of

inserting the sculpted rib cartilage.10,12,16,24 As the purpose of

this study was to determine whether a 3D model can be used

as an intraoperative tool or reference during surgery, the

photogrammetry evaluation will have to be performed in a

separate study.

The applications of 3D technology are limitless; for e.g., it

can be used for current and future techniques of ear

Table 2 e Lateral view comparison of 2D template andcasted ear model.

Lateral (%)

Patient 1 16.71

Patient 2 17.90

Patient 3 20.43

Patient 4 16.36

Patient 5 11.18

Patient 6 11.71

Patient 7 17.90

Standard deviation 3.39

Total average percentage difference ¼ 16.03%

Percentage difference between the lateral view of casted ear model

and traditional 2D template.

reconstruction, such as creating ear prostheses, biocompat-

ible ear scaffolds, and bioabsorbable scaffolds seeded with

cartilage stem cells. Current ear prostheses are created by

using a silicone mold of the ear but with 3D scanning and

printing; fabrication can be simplified by directly scanning the

ear and printing the prosthesis. Also, the shape of ready-made

Medpor inserts can be customized by using 3D scanning and

printing to create unique ear scaffolds matching each pa-

tient’s normal ear. The ultimate goal of regenerating an ear

with autologous tissue can be achieved by 3D printing bio-

absorbable materials like polycaprolactone with cartilage

stem cells seeded onto the 3D-printed bioabsorbable scaffold.

The feasibility of using polycaprolactone scaffolds and cell-

laden hydrogel as ear regeneration materials was demon-

strated by Lee et al.25 In optimal in vitro experiments, 3D

printing cell-laden materials with decellularized extracellular

matrix can be used to mimic the microenvironment.26

Culturing cartilage stem cells and appropriately positioning

an appropriate amount at the correct spot are the most diffi-

cult processes. If direct scanning, 3D printing of biocompatible

or bioabsorbable scaffolds, and seeding cartilage stem cells

can be performed, regenerating ear deformity with one’s own

tissue is possible in the near future.

Conclusions

The results of this clinical study demonstrate the usefulness

of 3D scan-to-print technology for microtia reconstruction.

We were able to fabricate the 3D-printed ear model and use it

as a reference tool to simplify microtia reconstruction. The

casted earmodelwas stable enough to allow the 3D scanner to

acquire sufficient details of the ear shape. The thickness,

depth, and height information of each patients’ 3D-printed ear

models were consistently and accurately represented and

helped surgeons sculpt the harvested rib cartilage and visu-

alize the ear of the affected side. Moreover, the provided 3D-

printed earmodel reassured surgeons for cartilage framework

when compared to using the traditional 2D template. The

availability of the 3D-printed ear model in the operating room

greatly benefits both patients and clinicians by reducing sur-

gery time and effort.

j e o n e t a l � f a b r i c a t i o n o f 3 d s c an - t o - p r i n t e a r m od e l 497

Acknowledgment

Authors’ contributions: B.J., C.L., and M.K. contributed equally

to this work as first authors. T.H.C. and S.K. contributed

equally to this work as corresponding authors.

This study was supported by grant 05-2015-0010 from the

Seoul National University Hospital Research Fund. This study

was also approved by the Institutional Review Board of the

Seoul National University College of Medicine/Seoul National

University Hospital.

Disclosure

The authors have no financial disclosures and report no con-

flicts of interest with any of the companies or products

mentioned in this article.

r e f e r e n c e s

1. Luquetti DV, Leoncini E, Mastroiacovo P. Microtia-anotia: aglobal review of prevalence rates. Birth Defects Res A Clin MolTeratol. 2011;91:813e822.

2. Suutarla S, Rautio J, Ritvanen A, et al. Microtia in Finland:comparison of characteristics in different populations. Int JPediatr Otorhinolaryngol. 2007;71:1211e1217.

3. Harris J, Kallen B, Robert E. The epidemiology of anotia andmicrotia. J Med Genet. 1996;33:809e813.

4. Mastroiacovo P, Corchia C, Botto LD, et al. Epidemiology andgenetics of microtia-anotia: a registry based study on overone million births. J Med Genet. 1995;32:453e457.

5. Kristiansen M, Oberg M, Wikstrom SO. Patients’ satisfactionafter ear reconstruction with autologous rib cartilage. J PlastSurg Hand Surg. 2013;47:113e117.

6. Flint PW, Cummings CW. Mirotia reconstruction. In: Sie KC,ed. Cummings otolaryngology: Head and neck surgery. 6th ed.Philadelphia, PA: Elsevier, Saunders; 2015.

7. Horlock N, Vogelin E, Bradbury ET, Grobbelaar AO, Gault DT.Psychosocial outcome of patients after ear reconstruction: aretrospective study of 62 patients. Ann Plast Surg.2005;54:517e524.

8. Soukup B, Mashhadi SA, Bulstrode NW. Health-relatedquality-of-life assessment and surgical outcomes forauricular reconstruction using autologous costal cartilage.Plast Reconstr Surg. 2012;129:632e640.

9. Anghinoni M, Bailleul C, Magri AS. Auricular reconstruction ofcongenital microtia: personal experience in 225 cases. ActaOtorhinolaryngol Ital. 2015;35:191e197.

10. Baluch N, Nagata S, Park C, et al. Auricular reconstruction formicrotia: review of available methods. Can J Plast Surg.2014;22:39e43.

11. Im DD, Paskhover B, Staffenberg DA, Jarrahy R. Currentmanagement of microtia: a national survey. Aesthetic PlastSurg. 2013;37:402e408.

12. Wilkes GH, Wong J, Guilfoyle R. Microtia reconstruction. PlastReconstr Surg. 2014;134:464ee479e.

13. Korus LJ, Wong JN, Wilkes GH. Long-term follow-up ofosseointegrated auricular reconstruction. Plast Reconstr Surg.2011;127:630e636.

14. Younis I, Gault D, Sabbagh W, Kang NV. Patient satisfactionand aesthetic outcomes after ear reconstruction with aBranemark-type, bone-anchored, ear prosthesis: a 16 yearreview. J Plast Reconstr Aesthet Surg. 2010;63:1650e1655.

15. Hatamleh MM, Watson J. Construction of an implant-retainedauricular prosthesis with the aid of contemporary digitaltechnologies: a clinical report. J Prosthodont. 2013;22:132e136.

16. Walton RL, Beahm EK. Auricular reconstruction for microtia:Part II. Surgical techniques. Plast Reconstr Surg.2002;110:234e249.

17. Kim H, Hwang JH, Lim SY, et al. Preoperative rib cartilageimaging in 3-dimensional chest computed tomography forauricular reconstruction for microtia. Ann Plast Surg.2014;72:428e434.

18. Lee LN, Boahene KD. A novel technique for sculpting costalcartilage in microtia repair and rhinoplasty. JAMA Facial PlastSurg. 2013;15:349e351.

19. Thadani SM, Ladani PS. A new method for training of earframework creation by silicon dental impression material.Indian J Plast Surg. 2012;45:134e137.

20. Shen C, Yao CA, Magee 3rd W, Chai G, Zhang Y. Presurgicalnasoalveolar molding for cleft lip and palate: the applicationof digitally designed molds. Plast Reconstr Surg.2015;135:1007ee1015e.

21. Murphy SV, Atala A. 3D bioprinting of tissues and organs. NatBiotechnol. 2014;32:773e785.

22. Choi JW, Kim N. Clinical application of three-dimensionalprinting technology in craniofacial plastic surgery. Arch PlastSurg. 2015;42:267e277.

23. Souzaki R, Kinoshita Y, Ieiri S, et al. Three-dimensional livermodel based on preoperative CT images as a tool to assist insurgical planning for hepatoblastoma in a child. Pediatr SurgInt. 2015;31:593e596.

24. Han K, Kim J, Kim J, Son D, Kim S, Choi TH. Novelreconstructive methods of the conchal central strut using anabsorbable plate after total harvesting of the conchalcartilage. Ann Plast Surg. 2015;74:549e556.

25. Lee JS, Hong JM, Jung JW, Shim JH, Oh JH, Cho DW. 3D printingof composite tissue with complex shape applied to earregeneration. Biofabrication. 2014;6:024103.

26. Pati F, Jang J, Ha DH, et al. Printing three-dimensional tissueanalogues with decellularized extracellular matrix bioink. NatCommun. 2014;5:3935.