=Paper=
{{Paper
|id=Vol-2744/paper62
|storemode=property
|title=The Significance of Computer Modeling and 3D Printing Technology for Facial Ectoprosthetics
|pdfUrl=https://ceur-ws.org/Vol-2744/paper62.pdf
|volume=Vol-2744
|authors=Svetlana Сherebylo,Vyacheslav Vnuk,Evgeniy Ippolitov,Mikhail Novikov,Pavel Mitroshenkov,Petr Mitroshenkov
}}
==The Significance of Computer Modeling and 3D Printing Technology for Facial Ectoprosthetics==
https://ceur-ws.org/Vol-2744/paper62.pdf
The Significance of Computer Modeling and 3D Printing
Technology for Facial Ectoprosthetics*
1[0000-0003-0502-9681] 1[0000-0003-2536-6626]
Svetlana Сherebylo , Vyacheslav Vnuk ,
1[0000-0002-0622-6727] 1[0000-0003-0626-793X]
Evgeniy Ippolitov , Mikhail Novikov ,
2[0000-0002-3315-3973] 2[0000-0002-7956-425X]
Pavel Mitroshenkov , Petr Mitroshenkov
1 Institute on Laser and Information Technologies RAS – Branch of the Federal Scientific Re-
search Centre “Crystallography and Photonics” of RAS, Shatura, Russia
2 FSBI ”Clinical hospital №1” (Volynskaya) of the Russian President Administration, Moskow,
Russia
novikov@rambler.ru
Abstract. The integration of information technologies in healthcare practice
significantly changes the methods of diagnosis and treatment, the forms of in-
teraction of doctors with patients and colleagues, the organization of treatment
and recovery of health. The field of reconstruction of the auricle is still a huge
challenge for facial plastic surgeons and requires at various techniques to find
the best treatment for each patient. The paper describes the application of com-
puter modeling and laser stereolithography technology in surgical practice for
auricular surfaces ectoprosthetics. To improve the accuracy and quality of the
surgical intervention the positioning of external prosthesis is applied with the
aid of personal templates and computer navigation. The accuracy of ectopros-
thesis positioning when using a plastic mask template was 0.3-0.4 mm, while
computer navigation was 0.1 - 0.2 mm. Using personalized templates is a sim-
pler and more intuitive way of positioning that does not require expensive com-
puter navigation systems. This example of ectoprosthetics shows the possibili-
ties of various reconstructions of facial organs, not only the ear, but also, for
example, the nose, using computer modeling and 3d printing technologies
Keywords: Computed Tomography, Digital Model, Computer Modeling, Addi-
tive Technologies, Reconstructive Surgery.
1 Introduction
The integration of information technologies in healthcare practice significantly
changes the methods of diagnosis and treatment, the forms of interaction of doctors
Copyright © 2020 for this paper by its authors. Use permitted under Creative Commons Li-
cense Attribution 4.0 International (CC BY 4.0).
* This work was done with the financial support of the RFBR (Grant MK # 18-29-03238).
Work on laser stereolithography is executed at financial support of the Ministry of science and
higher education (State task FSRC "Сrystallography and Photonics" RAS).
2 S. Cherebylo et al.
with patients and colleagues, the organization of treatment and recovery of health.
The field of ear reconstruction is still a huge challenge for facial plastic surgeons and
requires at various techniques to find the best treatment for each patient. Defects and
deformities of the ear include not only acquired defects associated with trauma, burns,
tumors, puncture defects, scars, and inflammation/allergies, but also congenital mal-
formations of the ear, ranging from grade I malformations (such as prominent ears) to
grade III malformations, including severe microtia changes. Depending on the defect
and the surrounding circumstances, restoring a full ear is always the main goal of the
patient and the plastic surgeon. In work [1], a fairly complete literary review of the
application of modern methods of ear restoration is presented. Surgical practice has
already acquired sufficient experience in using computer modeling and laser stereo-
lithography for planning reconstructive operations [2-3] to successfully apply them to
the treatment of patients.
The development of modern three-dimensional modeling and the introduction of a
new generation of spiral computed tomography significantly expanded the possibili-
ties of using information technologies in reconstructive surgery [4-8]. Specialized
software allows to quickly process the graphical data of the patient's examination and
create the digital three-dimensional models of any defect or pathology zone.
Digital models are increasingly used in the preparation and planning of surgery in
maxillofacial surgery. They can be directly employed to create copies of pathologies
and defects of a specific patient using additive technologies [2-4]. Personalized plastic
copies of anatomical structures allow for effective pre-planning of complex opera-
tions. Based on digital models of defects or pathology zones of specific human dis-
eases, can create unified databases for intelligent medical decision support systems. In
most studies [4-7], the data from a patient's tomographic examination are used to
create digital models. In [8-10], the photogrammetry method was applied to transform
photographic images into a three-dimensional model. The analysis of the research
shows that to create the most complete anatomical shape of the ear, especially with an
internal structure, it is preferable to use the graphical data of the patient's tomographic
examination.
The appearance of a man is primarily his face, and quite often there are situations
when a person as a result of mechanical injury, serious illness or birth defects suffers
from serious deformations of the face or from complete or partial absence of some of
its organs. Such defects of the maxillofacial area are the cause of aesthetic discomfort,
but modern medicine can solve this problem by performing reconstructive surgery to
install individual ectoprostheses created using 3D printing technologies, which allow
you to reproduce the anatomical model of a defective or lost organ with maximum
accuracy. 3D printing technology has found its place in various branches of medicine,
since its main advantage is the ability to create personalized models of various human
organs and structures [4, 11, 12]. A breakthrough technology in the field of recon-
structive surgery and implantology can be 3D-bioprinting — direct manufacturing of
implants and organs of the required shape and functionality from biomaterials. A
review of the current state of 3D-bioprinting shows that currently there are mainly
experimental works on the search for effective biomaterials and synthesis processes,
in practical surgery, bioprinting has not yet found direct application [13-16].
The Significance of Computer Modeling and 3D Printing Technology… 3
2 Creating digital models and a virtual project
The auricle has a complex anatomical structure, and to create an individual ectopros-
thetics at the initial stage, it is necessary to have the most accurate three-dimensional
representation of the anatomical changes of both bone and soft structures of the face.
The initial data for building a personal three-dimensional model of the patient are the
graphical data of the study on a computer tomograph [4].
To create virtual models, specialized software was used that allows to convert a set
of gray images into a three-dimensional model. To do this, the image is segmented
[17], and a certain threshold value is set for graying the image, which permits to sepa-
rate bone fragments and soft tissues [18]. This process is very important, because it
largely determines the accuracy and quality of the resulting digital models. STL mod-
els and specialized Magics software from Materialise, Belgium, were used for com-
puter modeling in this work. To restore the model of the reconstructed auricle, the
symmetry of the auricles was can use and a mirror image of the healthy zone was
applied (see Fig. 1).
a b
Fig. 1. Virtual project of soft tissue with the defect (a) and a mirror model (b).
Further work with the displayed auricle includes careful positioning of it. The
three-dimensional model must be installed with regard for all the anatomical nuances,
observing the proportions and symmetry. A number of software functions are used for
this, namely rotation, displacement, merger, subtraction, smoothing, etc (see Fig. 2).
a b
Fig. 2. Positioning of the 3D model (a) of ear reconstruction (b).
4 S. Cherebylo et al.
At the next stage of modeling, a model of template is created for the installation of
extraoral implants, i.e. the fixing points of the support beam structure for the installa-
tion of the ectoprosthetics (see Fig. 3).
a b
Fig. 3. Virtual project of positioning of the 3D model (a) for reconstruction (b).
To use the navigation systems during the operation, a virtual project was developed
(see Fig.4) for combining a digital model of the patient's facial skeleton with a de-
signed mask template for positioning the ectoprosthetics fixation elements.
Fig.4. Virtual project of operation planning.
3 Intraoperative computer navigation
One of the main trends in clinical medicine is the intraoperative use of high-precision
computer navigation, which allows improving patient’s safety during surgery, increas-
ing the accuracy of surgical interventions [19, 20]. The widespread use of microsurgi-
cal equipment and high requirements for the accuracy of the intervention have led to
the fact that even the best surgeons have almost reached the limit of their physical
The Significance of Computer Modeling and 3D Printing Technology… 5
capabilities. The use of multispiral computed tomography (MSCT) significantly im-
proved the 3-dimensional localization of the pathological process and increased the
accuracy of surgical intervention and development of new imaging techniques, in-
cluding an intraoperative one. The navigation system tracks the position of the in-
strument in the surgeon's hand and shows on the monitor how this instrument is posi-
tioned relative to the three-dimensional model of the patient created from preoperative
tomographic examinations. Navigation allows to simulate the course of the operation
on the three-dimensional reconstruction of the patient before performing surgical
manipulations.
The problem of eliminating deformations of the facial skeleton of acquired and in-
nate origin remains relevant to the present time. Complex spatial and geometric rela-
tionships between the facial skeleton and the contour of the soft tissues of the face
contribute to the formation of combined deformations and defects of the facial skele-
ton when it is damaged or abnormally developed. The use of the standard technique of
"template surgery" and individualization of the maxillofacial fixing and reconstructive
implants, which in some clinical cases perform the function of a template for the re-
position of bone fragments, is not always sufficient the possibility of achieving max-
imum accuracy of implant positioning. Currently, in order to improve the objectifica-
tion and accuracy of intraoperative positioning of facial skeleton fragments, the meth-
od of computer navigation using modern surgical navigation stations is successfully
applied.
The aim of the research was to develop an algorithm for applying the method of
virtual planning of surgical interventions and intraoperative computer navigation to
eliminate asymmetric deformities of the facial skeleton, to make a comparative analy-
sis of various methods of registering the patient's head when performing intraopera-
tive navigation.
All the patients underwent MSCT of the facial skeleton at the stage of preoperative
examination. Virtual planning of the operation was performed by the external soft-
ware Magics from Materialise, Belgium with the creation of a three-dimensional
model that was imported into the navigation station before the operation. Intraopera-
tive monitoring of the position of individual maxillofacial implants was achieved by
the STRYKER computer navigation station (USA) (see Fig.5).
Fig. 5. External view of the navigation station.
6 S. Cherebylo et al.
Registration of the patient's head was performed in two ways: by the invasive and
non-invasive contact methods. During the invasive registration method, the registra-
tion pins were installed in the patient's skull in the projection of the Nasion (N) point,
the zygomatic sutures, and at the base of the Spina Nasalis Anterior (SNA). Perform-
ing registration by the non-invasive contact method did not require pre-installation of
registration pins. The projections of points in the N region, the tip of the nose, and the
medial and lateral corners of the eyes were used as registration points. To correct the
registration error at the final stage of the procedure, additional registration points were
collected from the patient's forehead using a contact or non-contact method, i.e. with a
pointer or laser pointer. The external contour of displaced bone fragments and im-
plants on the virtual model of the facial skeleton was used as reference points for
eliminating post-traumatic deformations of the middle zone of the face. The position-
ing of implants in the postoperative period was monitored by combining a virtual
preoperative model with postoperative MSCT data imported into the navigation sta-
tion.
The analysis of the results of this study shows that the algorithm of intraoperative
navigation allows achieving high accuracy of positioning of maxillofacial and ex-
traoral implants. In this case, the accuracy of intraoperative control depends largely
on the accuracy of the patient's head registration procedure. So, according to our re-
search, the most accurate is the invasive method of registration, involving the use of
bone pins. The registration error was 0.2-0.3 mm. However, this method has a signifi-
cant drawback — the need for preliminary hospitalization of the patient for the pur-
pose of installing pins and performing MSCT. Only after this procedure, it is possible
to perform preoperative virtual simulation, which significantly increases the duration
of preoperative preparation. The non-invasive method of registering the patient's head
does not require pre-installation of pins, but the accuracy of this method, according to
our data, was lower, and the registration error was 0.6-0.7 mm. This error can be
compensated by collecting additional registration points from the skin surface of the
patient's forehead, which is provided for by the registration Protocol of navigation
stations. The combination of the preoperative virtual model and the results of the
control MSCT of the facial skeleton using the image overlay method in the navigation
station revealed an almost complete coincidence of the error in positioning of the
osteotomized fragments and implants by the reference points with the data on the
error in positioning of the registration points during the registration procedure of the
patient's head, which indicates the fundamental importance of this stage in the process
of intraoperative computer navigation. At the same time, the duration of the registra-
tion procedure did not significantly affect the overall duration of the surgical interven-
tion and when mastering sufficient skills in performing this stage of navigation, it
averaged 60 seconds. In order to achieve the maximum accuracy of modeling stand-
ard reconstructive implants, it is advisable to produce a stereolithographic model of
the mold for the final packing of a standard reconstructive implant using a stereolith-
ographic model of the patient's skull during preoperative preparation. Fig.6 presents a
clinical example of employment of intraoperative navigation when installing extraoral
implants to fix the ear ectoprosthetics.
The Significance of Computer Modeling and 3D Printing Technology… 7
Fig. 6. The use of intraoperative navigation during the installation of extraoral implants.
The model created as a result of virtual planning (see Fig.6) with extraoral implants
placed on it was imported to the Stryker navigation station. The positioning of bone
channels for implant placement was performed under the navigation control using a
navigation pointer. The final check of the implant position was also performed using a
pointer, as shown in Fig. 7.
a)
b)
Fig. 7. The stage of combining the virtual and postoperative models (the arrows indicate the
position of the implants); the position of the tip of the pointer (a) on the virtual model in on-line
mode (b).
8 S. Cherebylo et al.
In the postoperative period, when on combining the virtual model and the postop-
erative model of the patient's skull, the final control of the position of the extraoral
implants was exerted, as shown in Fig. 7b (the position of the implants is indicated by
the arrows).
4 Manufacturer of plastic models and their application
Preliminary analysis of additive manufacturing methods (FDM, SLS, SLA) shows
that laser stereolithography is the most promising technology for the production of
personal templates in terms of accuracy and purity of surface reproduction, ease of
processing and removal of residual material. To solve the problem of rapid production
of three-dimensional objects of complex shape based on their computer models for
medical applications, the LS150 laser stereolithography unit was developed at ILIT
RAS. Plastic models were made by laser stereolithography, which creates real objects
of complex shapes from a liquid photopolymer composition (see Fig. 8). The essence
of the process is that the liquid resin is cured layer by layer in a given geometric plane
under the influence of laser radiation [4].
Fig. 8. Plastic template of the mask model made by laser stereolithography.
The templates made by laser stereolithography was used during the operation for
positioning and installing ectoprosthesis fixation elements (see Fig. 9).
a) b)
Fig. 9. Application of plastic models when planning the installation (a) of an ectoprosthetics (b).
The Significance of Computer Modeling and 3D Printing Technology… 9
The ectoprosthetics itself was made of medical silicone by casting a plastic proto-
type. The silicone construction is absolutely identical to the skin color and feels very
similar to soft tissues (see Fig. 10).
Fig. 10. The result of the ectoprosthetics installation
5 Conclusion
In the presented clinical cases it has become possible, thanks to computer modeling,
the technology of laser stereolithography and computer navigation, to achieve full
recovery of the body with the proper proportions and facial aesthetics, as well as to
precisely position the clamping elements of ectoprosthetics (Fig.7, 10). The accuracy
of ectoprosthesis positioning when using a plastic mask template was 0.3-0.4 mm,
while computer navigation was 0.1 - 0.2 mm. Using personalized templates is a sim-
pler and more intuitive way of positioning that does not require expensive computer
navigation systems. This example of ectoprosthetics shows the possibilities of various
reconstructions of facial organs, not only the ear, but also, for example, the nose, us-
ing computer modeling and 3d printing technologies. Such surgical operations help to
solve the problem of aesthetic disorders and as a result allow a person to restore psy-
chological balance, socialize and gain self-confidence.
Acknowledgments
This work was done with the financial support of the RFBR (Grant MK # 18-29-
03238). Work on laser stereolithography is executed at financial support of the Minis-
try of science and higher education (State task FSRC "Сrystallography and Photonics"
RAS).
10 S. Cherebylo et al.
References
1. Storck, K.: Total Reconstruction of the Auricle: Our Experiences on Indications and Re-
cent Techniques. BioMed Research International 2014, ID 373286, 15 p. (2014).
2. Stuchilov, V. A.: Clinical aspects of the use of laser stereolithography in the surgical
treatment of injuries of the middle zone of the face. Clinical dentistry 3, 54-57 (RUS)
(2001).
3. Naumann, A.: Clinical aspects and strategy for biomaterial engineering of an auricle based
on three-dimensional stereolithography. European Archives of Oto-Rhino-Laryngology
260, 568–575 (2003).
4. Panchenko, V.Ya.: «Modern laser and information technologies», red., Interkontakt Nau-
ka, Moscow, (RUS) (2014).
5. Mitroshenkov, P. N.: Reconstructive surgery of total and Subtotal defects of the upper,
middle and lower zones of the facial skeleton. Synthesis of Books, Saint Petersburg,
(RUS) (2010).
6. Zeng, W.: Fused deposition modelling of an auricle framework for microtia reconstruction
based on CT images. Rapid Prototyping Journal 14(5), 280-284 (2008).
7. Guang-Ye, W.: Computer-assisted virtual preoperative planning in orthopedic surgery for
acetabular fractures based on actual computed tomography data. Computer Assisted Sur-
gery 21(1), 160-165 (2016).
8. Chen, Z.: Precision of three-dimensional stereo-photogrammetry (3dMD™) in anthropom-
etry of the auricle and its application in microtia reconstruction. Journal of Plastic, Recon-
structive and Aesthetic Surgery 68(5), 622-631 (2015).
9. Flores, R.: The technique for 3D printing patient-specific models for auricular reconstruc-
tion. Journal of Cranio-Maxillofacial Surgery 45(6), 937-943 (2017).
10. Zhou, J.: Three-dimensional autologous cartilage framework fabrication assisted by new
additive manufactured ear-shaped templates for microtia reconstruction Journal of Plastic.
Reconstructive and Aesthetic Surgery 69(10), 1436-1444 (2016).
11. Crafts, T.; Three-Dimensional Printing and Its Applications in Otorhinolaryngology– Oto-
laryngol. Head Neck Surg 156(6):999-1010 (2017).
12. Chae, Michael P.: Emerging applications of bedside 3D printing in plastic surgery. Fron-
tiers in Surgery Volume 2| Article 25 (2015).
13. Guangdong, Z.: In Vitro Regeneration of Patient-specific Ear-shaped Cartilage and Its First
Clinical Application for Auricular Reconstruction/ EBioMedicine 28, 287–302 (2018).
14. Kim, H.: Fabrication and characterization of 3D-printed elastic auricular scaffolds: A pilot
study. Laryngoscope 129(2), 351-357 (2019).
15. Zachary, G.: Applications of 3-Dimensional Printing in Facial Plastic Surgery. J Oral Max-
illofac Surg 74, 427-428 (2016).
16. Ji, Hyun Kim: Translation and Applications of Biofabrication. A. Ovsianikov . (eds.), 3D
Printing and Biofabrication, Reference Series in Biomedical Engineering. Springer Inter-
national Publishing AG (2016).
17. Musatyan, S.A.: Sposoby segmentacii medicinskih izobrazhenij. Trudy ISP RAN, 30(4),
183-194 (RUS) (2018).
18. Eijnatten, M.: The impact of manual threshold selection in medical additive manufactur-
ing, J CARS 12, 607–615 (2017).
19. Park, Y.M.: Transoral robotic surgery for hypopharyngeal squamous cell carcinoma: 3-
Year oncologic and functional analysis. Oral Oncology 48, 560-566 (2012).
20. Lazzara. B.M.: Cyberknife radiosurgery in treating trigeminal neuralgia. J Neurointerv
Surg. 5(1), 81-85 (2012).