Page 70 - IJB-8-2

A New 3D-Printed LNF Training Model
1. Introduction solubility in other solvents, silicone gel is widely used in
industry because of its excellent elasticity and resilience,
Three-dimensional (3D) printing is a technique that could chemical stability, thermal and electrical resistance,
enable the production of anatomically matched or patient- biocompatibility, and low permeability compared
specific device and allow high on-demand fabrication of with other polymer systems. Hydrogel is an attractive
products for medical application in highly cost-effective material used in medications attributed to its capability
manner . Highly accurate products derived from patient’s of absorbing and desorbing solvents in response to its
[1]
radiological imaging data were reportedly used in pre-
operative planning, counseling with patients, training of environment; however, this property of absorbing and
students and residents, surgical training, intraoperative desorbing solvents depends on restricted environmental
conditions, such as low humidity. With the availability
navigation, and templates or guides for specific task . of advanced materials and printing technique, there has
[2]
3D-printed models range from hard tissues such as bones been a growing number of surgical simulation models
to soft-tissue structures such as heart, liver, lung, and of soft tissues that are generated from different systems.
vasculature are used in surgical simulation for different
surgical procedures training. Compared to studies about The surgical models, including anatomical model and
hard tissues, however, studies about 3D-printed soft disease model, of liver and kidney are well-established;
tissue for surgical training are scarce. Unlike fabrication however, the studies on fabricating a stomach model
of hard tissue, simulations using soft tissues are limited are still scarce although researchers had attempted to
by the simulation of mechanical properties, which vary simulate mechanical properties in an anthropomorphic
[7,12,13]
between organs or individuals [3,4] . There are several gastric model . The structures and organs in human
types of methods in 3D printing available for soft- have specific physical properties (for dissection), which
tissues fabrication, including material extrusion (fused differ from one other. For example, the texture of liver
deposition modeling and [FDM] and direct ink writing), is softer than stomach, although they are both made of
vat photopolymerization (VP), material jetting, and soft tissue. This should be considered in the process of
powder jet fusion [4,5] . Different printing materials and creating an organ or disease model. Tissue response to
techniques are chosen depending on their benefits and surgical insults also should be considered. For example,
limitations, especially in 3D bioprinting area, considering the materials used should respond well during dissection
[14]
that the unique living or bioactive materials (bioink) used by harmonic scalper .
and the type of methods used are usually determined by Laparoscopic Nissen fundoplication (LNF) is a
the desired materials . Various requirements, including surgical treatment option for gastroesophageal reflux
[6]
appearance similarities, mechanical properties similarities, disease (GERD). GERD is a common disease with
and simulations of true organ environment, should be typical symptoms of acid regurgitation and heartburn, and
taken into consideration when researchers or companies complications including esophagitis, peptic strictures,
select the appropriate printing strategies . As one of the and Barrett esophagus. The application of LNF requires
[7]
[15]
methods used in early phase, material jetting is low cost high levels of expertise and training . Developed by
and has high printing speed, but this technique demands Dr. Rudolf Nissen, the use of LNF started as early as 1955
high criteria and standards for bioinks used, especially in and was well established in Western countries, whereas at
viscosity and clotting issue. Material extrusion, a process the same time, its application was still at its initial stage
[16]
driven by pressure, allows the use of viscous liquid, such in China . Relatively low prevalence (1.9–7%) in China
as cell suspension at a high density, but has a relatively coupled with delayed developments of surgical treatment
slow printing speed and low resolution. Powder jet fusion of GERD had limited training or practicing opportunities
was also an economic choice for fast and stable printing of laparoscopic anti-reflux surgery for residents or
[17]
of soft tissue, while may more effort in post-processing attendings . Nissen fundoplication was not included
modification is needed due to residual powder that leads in the national textbook for medical college student
to low surface accuracy and deficient structure. VP, until 2018; therefore, most of the Chinese students are
including stereolithography, digital light processing, and unfamiliar about this surgical technique. Watching
two-photon polymerization, allows a relatively quick and recorded video or direct observation of surgery are how
precise fabrications of sophisticated internal or external most surgeons are trained but in the absence of practices.
anatomical structures [8-11] . Polyurethane, silicone gel, and Cadaver model, animal model, and ex vivo organ
hydrogels are some of the most commonly used materials model are common wet laboratory models used in
in soft-tissue printing. Polyurethane can be combined laparoscopic surgery training [14,18] . However, due to the
with other hydroxyl or amine polymers, offering a concerns of high cost, social stress, and biosafety issue,
changeable designation of chemical backbone, which can the need for more proper alternatives to the wet laboratory
achieve different mechanical performances, but these can models is emerging [19,20] . At present, animals such as
be a concern of toxicity and flammability. Despite low swine, rats, or mouse are still the most widely used models

62 International Journal of Bioprinting (2022)–Volume 8, Issue 2