A novel anatomical thin titanium mesh plate with patient-matched bending technique for orbital floor reconstruction

Accepted Manuscript A Novel Anatomical Thin Titanium Mesh Plate with Patient-matched Bending Technique for Orbital Floor Reconstruction Chih-Hao Chen, MD, PhD, Po-Fang Wang, MD, Yu-Tzu Wang, MS, PhD, Pin-Hsin Hsu, MS, Chun-Li Lin, PhD, Professor PII:

S1010-5182(18)30123-9

DOI:

10.1016/j.jcms.2018.04.014

Reference:

YJCMS 2956

To appear in:

Journal of Cranio-Maxillo-Facial Surgery

Received Date: 16 November 2017 Revised Date:

26 March 2018

Accepted Date: 10 April 2018

Please cite this article as: Chen C-H, Wang P-F, Wang Y-T, Hsu P-H, Lin C-L, A Novel Anatomical Thin Titanium Mesh Plate with Patient-matched Bending Technique for Orbital Floor Reconstruction, Journal of Cranio-Maxillofacial Surgery (2018), doi: 10.1016/j.jcms.2018.04.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A Novel Anatomical Thin Titanium Mesh Plate with Patient-matched Bending Technique for ACCEPTED MANUSCRIPT Orbital Floor Reconstruction Chih-Hao Chen, Po-Fang Wang, Yu-Tzu Wang, Pin-Hsin Hsu and Chun-Li Lin

*

RI PT

Chih-Hao Chen, MD, PhD Craniofacial Research Center, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan Chang Gung University, College of Medicine 5, Fu-Hsin Street, Kwei-Shan, Taoyuan, Taiwan Tel: 886-3-328-1200, ext. 2946 Fax: 886-3-328-9582 E-mail: [email protected]

M AN U

SC

Po-Fang Wang, MD Department of Plastic and Reconstruction Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan. Tell: 886-3-3281200 ext. 2946 Fax: 886-3-3289582 Email: [email protected] Address: 5. Fu-Hsing Street. Kueishan, Taoyuan, Taiwan. 333 Email: [email protected]

TE D

Yu-Tzu Wang, MS, PhD student Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. Tel: 886-2-28267000 ext. 5571 Fax: 886-2-28210847 Email: [email protected] Address: No.155, Sec.2, Linong Street, Taipei, 112

AC C

EP

Pin-Hsin Hsu, MS Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. Tel: 886-2-28267000 ext 5405 Email: [email protected] Address: No.155, Sec.2, Linong Street, Taipei, 112

*Corresponding author: Chun-Li Lin, PhD, Professor, Department of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan. Tel: 886-2-28267000 ext. 7039 Fax: 886-2-28210847 Email: [email protected] Address: No.155, Sec.2, Linong Street, Taipei, 112

1

ACCEPTED MANUSCRIPT

RI PT

Chih-Hao Chen, Po-Fang Wang, Yu-Tzu Wang, Pin-Hsin Hsu and Chun-Li Lin*

Abstract

SC

This study developed an anatomical thin titanium mesh (ATTM) plate for Asian orbital floor fracture based on the medical image database. The computer aided stamping analysis was

M AN U

performed on four hole/slot patterns included the control type without hole design, circular hole pattern, slot pattern and hole/slot hybrid patterns within the ATTM plate with upper/lower dies of averaged orbital cavity reconstruction models. The curved-fan ATTM plate with 0.4mm thickness was manufactured and pre-bent using a patient matched stamping process to verify its

TE D

feasibility and the interfacial fitness between the plate and bone on the orbital floor fracture model. The stamping analysis found that the hole/slot hybrid patterns design resulted in the most favorable performance among all designs owing to the lowest maximum von-Mises stress/strain

EP

and spring-back value. The interfacial adaption results test showed that the average patient-matched stamping bending gap size was only 0.821mm and the operative time was about

AC C

8 seconds. This study concluded that the curved-fan ATTM plate with hole/slot hybrid pattern design and patient-matched pre-bent technique can fit the ATTM plate/orbital cavity interface well, decrease unstable fracture segment mobility and improve the overall reduction efficiency.

Keywords: orbital floor fracture, plate, stamping analysis, patient-matched, bending

1

ACCEPTED MANUSCRIPT

Introduction The orbital floor fracture is described as a fracture medial to the infra-orbital nerve and

RI PT

frequently associated with medial wall fractures (Nolasco and Mathog 1995; Burm et al., 1999; Manolidis et al., 2002; Metzger et al., 2006). The complications of enophthalmos, diplopia and visual acuity disturbance might be caused by incorrect anatomical orbital dimension

SC

reconstruction (Rana et al., 2015). Commercial titanium fan plates have been shown

biocompatible and available to offer rigid support for larger defects (Nolasco and Mathog 1995;

M AN U

Burm et al., 1999; Manolidis et al., 2002; Ellis and Tan 2003; Metzger et al., 2006; Rana et al., 2015). However, accurate contouring and alignment to fit the complex bony orbit geometry for each individual patient during surgery is still in high demand. Contouring the accuracy and fit of individualized commercial titanium fan plates requires extensive preparation. Residual stress during repeated contouring (bending) of the titanium fan plates also increases the risk of fatigue

TE D

failure for the bone plates (Champy 1980; Huang et al., 2016). The preformed orbital implants based on topographical orbital cavity analysis was proposed

EP

for incorrect orbital reconstruction improvement. This developed preformed implant was used to design an anatomical preform orbital implant covering the orbital floor and medial wall fitting

AC C

for most individuals, available at once without additional efforts (Metzger et al., 2007; Bittermann et al., 2014). However, this preformed implant did not focus specifically on orbital osteology in certain populations and still requires contouring to fit the interface. Compared with white and American populations, Asians (Chinese) have shorter distances from the anterior lacrimal crest to the more posteriorly located optic canal (Cheng et al., 2008). This phenomenon implies that anatomical variants in different populations may affect preformed implant covering size and fitness accuracy to the orbital cavity. 2

ACCEPTED MANUSCRIPT

Some surgeons used the relatively premorbid shape of the contralateral orbit and mirrored the data to the injured side based on the patient’s CT data to fabricate a stereo lithographic model to assist with accurate intraoperative bending (Baino 2011). Precise CAD/CAM milling

RI PT

technique and additional manufacturing (or 3D printing) were employed to manufacture titanium implants to be used in orbit reconstruction surgery and obtained excellent clinical outcomes (Kozakiewicz et al., 2009; Baino 2011; Huang et al., 2016). However, they are costly, time

SC

consuming and not available at all institutions. Developing a suitable anatomical thin titanium mesh (ATTM) plate based on a specific population and integrating a patient-matched bending

M AN U

technique to increase the interfacial fit adaption between the ATTM plate and orbital wall is necessary.

This study developed an ATTM plate profile for the orbital floor fracture based on the Asian medical image database and the optimal hole/slot pattern designed within the plate utilized

TE D

computer aided stamping analysis for laser cut manufacturing. A patient-matched bending technique was developed to increase the interfacial fit adaption between the ATTM plate orbital

AC C

EP

wall using integrated reverse engineering, 3D printing and stamping techniques.

Materials & methods

ATTM plate design profile This study collected at least 100 normal orbital cavity images from Taiwanese patients without traumatic deformation, including 50 males and 50 females over 18 years old. All images were obtained using a 0.4mm computed tomography (CT) scan interval. Image resolution was

3

ACCEPTED MANUSCRIPT

ensured by the Department of Plastic and Reconstructive Surgery at Chang Gung Memorial Hospital (IRB NO.201601297B0), Taiwan. The curved-fan ATTM plate profile was referenced

floor to medial wall) in our previous study (Hsu 2017) (Fig. 1).

SC

ATTM plate computer aided stamping analysis

RI PT

from the projection profile on the transverse plane of the averaged orbital concave surface (from

M AN U

Six regions (from A to F) distributed on the orbital floor and medial wall were defined to understand the most common orbital wall fractured area percentage from 50 collected orbital floor fracture CT scan images (Fig. 1).

The hole/slot pattern designed within the ATTM plate is maximized to provide enough

TE D

strength with minimum plate volume to prevent postoperative infection or discomfort. The ATTM plate mechanical strength must be considered to ensure capability when the plate is stamped to avoid buckling with spring-back value reduction and the risk for plate damage. The

EP

corresponding D+E region, the most common orbital wall fracture area within the ATTM plate, is designed as a solid plate section to isolate the orbital contents while providing sufficient

AC C

postoperative support for preventing enophthalmos and diplopia. Other regions within the ATTM plate were designed with four hole/slot patterns to perform the stamping analysis. Type 1 was a control type without hole design, Type 2 was designed with a circular hole pattern, Type 3 was designed with a slot pattern and Type 4 was designed with a hole/slot hybrid pattern (Fig. 2). The ATTM plate with four hole/slot patterns and the tool(lower)/core(upper) die solid models were imported into the Form Advisor package (Form Advisor V3.4.3, C3P Engineering

4

ACCEPTED MANUSCRIPT

International CO., New York, USA). Computer aided stamping analysis was then performed (Fig. 3(a)). The stamping tool die (cavity die/lower die) was the typical (averaged) orbital concave surface reconstructed from medical image database. The core (upper die) was created using

RI PT

Boolean operations in the CAD system (Creo Parametric v2.0, PTC, Needham, MA, USA). Four free mesh models were generated using the brick structural solid element as listed in

SC

Table 1. The plate material properties of the Grade 2 titanium including elasticity modulus,

Poisson ratio, yield strength and ultimate strength were 105GPa, 0.37, 0.303GPa and 0.462 GPa,

M AN U

respectively and applied from the literature (Hsu 2017). The tool and core dies set as rigid body, coefficient of friction and stamping speed were 0.1 and 2m/s, respectively for stamping analysis conditions. The analysis stop condition was assumed when the core (upper) die is moved to the lower die 0.4mm. The von-Mises stress, von-Mises strain and ATTM plate spring-back value for

TE D

each design were recorded to estimate the deformation and risk for plate fracture.

EP

ATTM plate manufacture, patient-matched bending and applications The laser cutting manufacturing process with high-power energy (SUPER TURBO-X 48,

AC C

Yamazaki Mazak Co., Florence, USA) was employed to cut the 0.4mm thickness design Type 4 ATTM plate (Fig. 3(b)). In order to verify the ATTM plate feasibility for orbital floor fracture, one random case in which the fracture type contained the orbital floor to medial wall was selected as the test sample. The corresponding orbital floor fracture image models were reconstructed in the CAD system. A stamping platform included core die (upper die), tool (cavity die/lower die) and alignment rods designed and duplicated as ABS (ABS-P430, Strayasys, Ltd., Minnesota, USA) models using a 3D printer (Dimension 1200es SST, Strayasys, Ltd., Minnesota, 5

ACCEPTED MANUSCRIPT

USA) (Fig. 4(a)). The stamping platform was clamped onto the punching machine with a 5 ton level to develop the patient-matched bending technique. Stamping was a single stage operation using a punching machine press where every press stroke produced the desired form on the plate.

RI PT

The curved-fan ATTM plate was placed in the tool to perform the sheet-metal forming

manufacturing process. Figure 4(b) shows the already bent curved-fan ATTM plate, fixed onto

SC

the ABS bone model.

M AN U

Interfacial adaption test

An interfacial adaption test was performed to compare the bone plate/orbital wall interfacial gap sizes between patient-matched stamping bending and manual pre-bending for ATTM plates to evaluate the interfacial fitness accuracy. The corresponding ABS plastic orbital floor fracture

TE D

model was duplicated using a 3D printer by setting application software (CatalystEX 4.4) to the Sparse-high density function with high manufacturing resolution. Three ATTM plates pre-bent using the stamping technique and manually contoured by our surgeon were fixed into the desired

EP

position to match the resting bone surface of the corresponding orbital floor fracture ABS bone

AC C

models. All samples, including the curved-fan ATTM plate and orbital floor ABS bone models, were scanned using CT to reconstruct 3D images with the gap sizes between the thin plate and plastic bone at 3 points (1-3 points) using four section slices (A-D sections) perpendicular to the plates. All samples were measured to evaluate the interfacial adaption fitness (Fig. 5).

Results

6

ACCEPTED MANUSCRIPT

Of the 50 orbital floor fracture patients evaluated, 30 were men (60%) and 20 were women (40%). The mean age was 31.5 years, ranging from 18 to 64 years old. The statistical result showed that the most common orbital wall fracture area was the floor, i.e. regions D and E and

RI PT

the fracture percentages were 64% and 58%, respectively. Combined wall fractures were

frequent as shown in Table 2. This result indicated that corresponding areas in the ATTM plate

SC

were designed as solid plate to isolate the orbital contents to support the soft tissue.

The stamping analysis showed that the highest maximum von-Mises stress/strain value of

M AN U

956MPa/0.7937 was found in the ATTM plate with Type 3 slot pattern (Fig. 6). This observation indicated that the ATTM plate with Type 3 design might increase the rupture risk after stamping owing to the residual stress/strain found within the plate. Although the design Type 2 circular hole pattern decreased the stress/strain value, the excessive spring-back value of 0.4432mm implied large error plate deformation from stamping may influence the accuracy in assisting the

TE D

fracture reduction. In general, these results indicate that Type 4 with the hole/slot hybrid pattern produced the best buckling deformation capability with the lowest risk for inducing stamping rupture (Fig. 6). The ATTM plate was then designed based on Type 4 due to its optimal

EP

mechanical behaviors (stress, strain and spring-back) among all designed stamping analysis cases

AC C

(Fig. 6). Figure 7 shows the von-Mises stress, von-Mises strain and spring-back value distributions for the four design types. The interfacial adaption results test showed that the average gap sizes in patient-matched stamping bending and manual pre-bending were 0.821mm±0.63mm and 2.285±1.82mm, respectively. Significant differences were found between plates using patient-matched stamping bending and manual bending. The average gap size value using manual contouring was about 2.78 times that using the stamping technique. The operation times were measured at about 8 7

ACCEPTED MANUSCRIPT

seconds and 7 minutes for the stamping technique and manual contouring, respectively. These results implied that the accuracy and feasibility for developing an ATTM plate with stamping

RI PT

patient-matched the manual pre-bent technique.

Discussion

SC

Inserting alloplastic material for supporting the soft tissue and to reshape the cavity is often

M AN U

indicated (Huang et al., 2016). Orbital wall constructions with more stable bridging materials are essential and depend on the defect size and location. Differences in the anatomical information were encoded from the literature for altered human races (Cheng et al., 2008). The intention was to design an anatomical orbital thin plate based on the medical image database covering the orbital floor and medial wall fitting for most individuals. CT data from unaffected orbital cavities

TE D

can be used for topographical analysis evaluations and mean orbital floor and medial wall shapes were recalculated to obtain a curved-fan ATTM flattened profile from the projection of the

2014).

EP

averaged orbital concave surface to transverse plane (Manolidis et al., 2002; Bittermann et al.,

AC C

The most common orbital wall fractured area found from the statistical orbital floor fracture CT scan images was designed as a solid region within the curved-fan ATTM plate to support the orbital contents. Other regions were designed to minimize the volume to prevent postoperative infection/discomfort. However, the hole/slot pattern design criterion within the plate needs to provide enough strength for stamping manufacturing, easy trimming operations and controlled hole/slot dimensions during laser cutting manufacturing. The computer aided stamping result showed that Type 4 with hole/slot hybrid pattern presented the optimal mechanical behaviors 8

ACCEPTED MANUSCRIPT

(lowest stress/strain/ spring-back values) with the lowest risk for stamping rupture and with best buckling deformation capability. The slots designed in the Type 4 plate were along the outer contour of the curved-fan ATTM plate to allow the clinician to trim the plate according to the

RI PT

defect size during the surgical operation. Otherwise, the hole and slot diameters were designed as 1.3mm and 1mm, respectively, under the laser cutting resolution (0.5mm). Therefore, the

proposed curved-fan ATTM plate was then designed based on Type 4 with five arms added at

SC

the anterior aspect of the plate for screw fixation at the anterior inferior orbital rim (Fig. 3(b)).

M AN U

CNC milling manufacturing with a metal 3D printer was used to produce the customized orbital implant with predefined preform thin orbital floor plate using CT image editing. However, the extremely high cost for CNC milling and thin layer manufacturing resolution of 3D printing with complex 3D structure for the customized orbital implant present real clinical application challenges. Regarding the use of archived contouring (bending) to fit the bony orbit for thin

TE D

titanium mesh plate, some surgeons use sterilized skull models to assist with intraoperative bending. Various aluminum templates with different sizes generated from topographical CT data previously obtained from normal subjects were also used to assist with pre-bent molded titanium

EP

mesh fan plates (Manolidis et al., 2002; Metzger et al., 2007). However, they are cost and time

AC C

intensive and not available for high precision reconstruction. The most appropriate orbital mesh needs to be stable, thin, preferably preformed, easy in handling, and reasonable in cost. To address these issues this study developed a curved-fan ATTM plate based on Asian populations. The laser cutting technique was employed to reduce the manufacturing cost. The patient-matched bending technique was settled by using the already very common FDM 3D printing to produce individualized tools and stamping the thin plate on a punching machine to form the patient-matched profile. Small gap size (about 0.8mm) at the 9

ACCEPTED MANUSCRIPT

bone/ATTM plate interface and rapid high efficiency forming (8 second) verified the feasibility of the developed patient-matched pre-bent technique.

RI PT

Some limitations must be noted in this study. Although duplicating the stamping die/tool using 3DP presents the greatest advantage in made-to-order (custom) implants, the greatest

positive impact is the timing required for surgery with competitive cost for small production runs

SC

(Rana et al. 2015). The 3DP material must have the strength to meet the stamping manufacturing process requirements. Otherwise, high-power laser cutting leads to surface accumulated carbon

M AN U

that may require attention due to the biocompatibility regulations for medical implants. The current patient-matched pre-bent on curved-fan ATTM plate is only available in vitro plastic

Conclusions

TE D

ABS bone model and further practical clinical testing is needed for further improvement.

The curved-fan ATTM plate is suitable for use in orbital floor fracture treatment based on

EP

the Asian normal orbital cavity image database providing reliable ATTM plate/orbital floor interface fit. The stamping manufacturing process using a custom 3DP die/tool can facilitate the

AC C

preoperative patient-matched bending technique, provides fractured bone profile, and improves the overall reduction efficiency for individual patients.

Ethical statement Ethical approval was not required.

10

ACCEPTED MANUSCRIPT

Funding No funding was available.

RI PT

Contributions

CH Chen, PF Wang and CL Lin conceived and designed the experiments; PF Wang, YT Wang and PH Hsu performed the simulation, experiment and analyzed the data; CH Chen and

SC

CL Lin wrote the manuscript; and all authors read and approved the final version of manuscript.

M AN U

Competing interests None declared. Source of support

TE D

This study is supported in part by MOST project 106-2221-E-010-006-MY3 and

AC C

EP

107-2622-8-010 -002 -TB1 of the Ministry of Science and Technology, Taiwan.

11

ACCEPTED MANUSCRIPT

References Baino F: Biomaterials and implants for orbital floor repair. Acta Biomater 7(9): 3248-3266, 2011

RI PT

Bittermann G, Metzger MC, Schlager S, Lagrèze WA, Gross N, Cornelius CP, Schmelzeisen R: Orbital reconstruction: prefabricated Implants, data transfer, and revision surgery. Facial Plast Surg 30(5): 554-560, 2014

SC

Burm JS, Chung CH, Oh SJ: Pure orbital blowout fracture: new concepts and importance of

M AN U

medial orbital blowout fracture. Plast Reconstr Surg 103(7): 1839-1849, 1999 Champy M: Surgical treatment of midface deformities. Head Neck Surg 2(6): 451-465, 1980 Cheng AC, Lucas PW, Yuen HK, Lam DS, So KF: Surgical anatomy of the Chinese orbit.

TE D

Ophthal Plast Reconstr Surg 24(2): 136-141, 2008

Ellis E III, Tan Y: Assessment of internal orbital reconstructions for pure blowout fractures: cranial bone grafts versus titanium mesh. J Oral Maxillofac Surg 61(4): 442-453, 2003

EP

Hsu PH: Development of the customized pre-bent orbital titanium plate. National Yang-Ming

AC C

University, Taiwan(ROC), 2017

Huang SF, Lo LJ, Lin CL: Biomechanical optimization of a custom-made positioning and fixing bone plate for Le Fort I osteotomy by finite element analysis. Comput Biol Med 68: 49-56, 2016 Kozakiewicz M, Elgalal M, Loba P, Komunski P, Arkuszewski P, Broniarczyck- Loba A, et al. Clinical applications of pre-bent titanium implants for orbital floor fractures. J Cranio-Maxillo-Facial Surg 37: 229-234, 2009

12

ACCEPTED MANUSCRIPT

Lieger O, Richards R, Liu M, Lloyd T: Computer-assisted design and manufacture of implants in the late reconstruction of extensive orbital fractures. Arch Facial Plast Surg 12(3):186-191, 2010

RI PT

Manolidis S, Weeks BH, Kirby M, Scarlett M, Hollier L: Classification and surgical management of orbital fractures: experience with 111 orbital reconstructions. J Craniofac Surg 13(6):726-737, 2002 Metzger MC, Schon R, Tetzlaf R, Weyer N, Rafii A, Gellrich NC, Schmelzeisen R:

SC

Topographical CT-data analysis of the human orbital floor. Int J Oral Maxillofac Surg 36(1): 45-53, 2007

M AN U

Metzger MC, Schon R, Weyer N, Rafii A, Gellrich NC, Schmelzeisen R, Strong BE: Anatomical 3-dimensional pre-bent titanium implant for orbital floor fractures. Ophthalmology 113(10): 1863-1868, 2006

Nolasco FP, Mathog RH: Medial orbital wall fractures: classification and clinical profile.

TE D

Otolaryngol Head Neck Surg 112(4): 549-556, 1995 Rana M, Gellrich MM, Gellrich NC: Customised reconstruction of the orbital wall and

208-209, 2015

EP

engineering of selective laser melting (SLM) core implants. Br J Oral Maxillofac Surg 53(2):

2014

AC C

Ventola CL: Medical applications for 3D printing: current and projected uses. P&T 39(10):704,

13

ACCEPTED MANUSCRIPT

Table 1. Element and node numbers for four free mesh designed models and averaged upper/lower die in computer aided stamping analysis.

Model

Lower Type1 die

833

2431

Element

1560

4732

Type3

Type4

5583

5284

4230

5461

5574

4968

3769

5003

AC C

EP

TE D

Node

M AN U

type

Type2

SC

Upper die

RI PT

Number of elements and nodes of each model in stamping analysis

14

ACCEPTED MANUSCRIPT

Table 2. The combined orbital wall fractures in 50 orbital floor fracture patients and presented in percentage.

A

B

C

D

24

20

13

32

48.0

40.0

Percentage

26.0

AC C

EP

TE D

(%)

M AN U

Number (people)

E

SC

Region

RI PT

Number of common orbital wall fractured

15

64.0

F

29

16

58.0

32.0

ACCEPTED MANUSCRIPT

Figure captions: Fig. 1 The curved-fan ATTM plate profile was obtained from the projection profile on the

RI PT

transverse plane of the averaged orbital concave surface (from floor to medial wall). Six regions (from A to F) distributed on the orbital floor and medical wall were defined to understand the most common orbital wall fracture area percentage from 50 collected orbital floor fracture CT

M AN U

SC

scan images.

Fig. 2 Four hole/slot patterns were designed within the ATTM plate to perform the stamping analysis. (a) Type 1: control type without hole design; (b) Type 2: circular hole pattern; (c) Type

TE D

3: slot pattern and (d) Type 4: hole/slot hybrid pattern.

Fig. 3 (a) Mesh patterns of four hole/slot designed patterns of the ATTM plate (right part) and the tool(lower)/core(upper) die (left part). (b) The curved-fan ATTM plate with 0.4mm thickness

AC C

EP

was manufactured using high-power energy laser cutting.

Fig. 4 (a) A stamping platform included core die (upper die), tool (cavity die/lower die) and alignment rods duplicated as ABS material using a 3D printer. The curved-fan ATTM plate was placed in the tool to perform the sheet-metal forming manufacturing process. (b) The already bent curved-fan ATTM plate and fixed on the ABS bone model.

16

ACCEPTED MANUSCRIPT

Fig. 5 Illustrations of the gap sizes evaluated between the thin plate and plastic bone at 3 points

RI PT

(1-3 points) using four section slices (A-D sections) perpendicular to the plates.

Fig. 6 The highest maximum von-Mises stress/strain and spring-back values of four hole/slot

SC

designed patterns within the ATTM plate in the computer aided stamping.

M AN U

Fig. 7 The von-Mises stress, von-Mises strain and spring-back value distributions for four design

AC C

EP

TE D

types. (a) stress; (b) strain and (c) spring-back.

17

Floor area

SC

Medial wall area

RI PT

ACCEPTED MANUSCRIPT

M AN U

Projection

Transverse plane

Projection profile

E

C B

D

Inferior orbital fissure

TE D

F

A

AC C

EP

Plate profile

Fig. 1

18

F

E

D

B

A

C

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

D+E

∅

2mm

TE D

1.75mm

EP

(a)

∅

∅ ∅

AC C

D+E

(b)

D+E

1.4mm

∅

1.3mm

1.8mm

∅

1mm

(c)

(d)

Fig. 2 19

RI PT

ACCEPTED MANUSCRIPT

EP AC C

ATTM plate

TE D

M AN U

SC

Core(upper die)

20

ACCEPTED MANUSCRIPT

RI PT

Tool(lower die)

AC C

EP

TE D

M AN U

SC

(a)

21

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

TE D

Five arms for screw fixation

AC C

EP

(b)

Fig. 3

22

SC

RI PT

ACCEPTED MANUSCRIPT

M AN U

Core

AC C

EP

Tool

TE D

ATTM plate

23

Alignment rods

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

(a)

24

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

(b)

AC C

EP

Fig. 4

25

RI PT

ACCEPTED MANUSCRIPT

M AN U

SC

Extension of Nosal bone

AC C

EP

TE D

(a)

(b)

Fig. 5 26

RI PT

ACCEPTED MANUSCRIPT

1200

800

600 Type1

956

M AN U

1000

SC

0.7937

Type2

TE D

400

200

AC C

EP

0

27

0.5 0.45 0.4 0.35 0.3 0.25

Type3

0.2 Type4 0.15 0.1 0.05 0

0.4432

SC

0.9

RI PT

ACCEPTED MANUSCRIPT

0.8

M AN U

0.7 0.6 0.5 0.4

TE D

0.3 0.2 0.1

0 Unit:mm

EP

Unit:Mpa

AC C

Fig. 6

28

ACCEPTED MANUSCRIPT

Type1

Type2 462.0 379.2

RI PT

296.5 213.

131.0

Type4

Type3

48.

-34.5

-117.

SC

-200.

M AN U

Unit： ：Mpa

(a)

Type2

TE D

Type1

Type3

0.250 0.219 0.188

Type4

0.125 0.094

EP AC C

0.156

0.063 0.031 0.000

(b) Type1

Type2

0.300 0.263 0.225 0.188

Type4

Type3

0.150 0.113

29

0.075 0.038 0.000

Fig. (c)7

Unit： ：mm