Application of a three-dimensional-printed endoscopic retrograde cholangiopancreatography simulation operation model in surgical training and teaching

Abstract

BACKGROUND

Three-dimensional (3D)-printed models have been widely applied in the medical field and play roles in preoperative simulation, surgical training, and education for young doctors. Compared with traditional imaging data, 3D-printed models are more intuitive, more accurate, and more operable, providing valuable support for clinical and educational purposes.

AIM

To create an endoscopic retrograde cholangiopancreatography training model for the diagnosis and treatment of common bile duct stones. The model includes key anatomical components and is suitable for simulating critical steps of the operation process.

METHODS

The model will serve as a valuable training tool for young doctors, enhancing their skills and understanding of the procedure. Young doctors were divided into two groups: A model-based teaching group and a group that received only theoretical and surgical video training. The two groups were evaluated and analyzed based on six indicators.

RESULTS

Both the model simulation group and the control group showed significant improvements in their grasp of theoretical knowledge. However, compared with the control group, the experimental group demonstrated notably greater improvement in several key areas, including understanding biliary anatomy, patient management, awareness of complications, confidence in performing procedural steps, and overall self-confidence (P < 0.001, P = 0.04, P = 0.036, P < 0.001, P = 0.012, respectively).

CONCLUSION

The 3D-printed endoscopic retrograde cholangiopancreatography simulator appears to be a feasible adjunct for junior doctor training, but larger studies are needed to confirm its effectiveness.

Key Words: Common bile duct stones; Three-dimensional printing; Endoscopic retrograde cholangiopancreatography; Operation model; Surgical training and teaching

Core Tip: Endoscopic retrograde cholangiopancreatography (ERCP) is technically demanding and difficult for beginners to master through traditional teaching alone. In this study, we developed a three-dimensional (3D) printed ERCP simulation model that incorporated key biliary anatomical structures for procedural training. Compared with conventional theoretical and video-based instruction, the model significantly improved trainees’ understanding of biliary anatomy, procedural proficiency, and learning confidence, suggesting that 3D-printed simulation models may represent an effective tool for ERCP training and surgical education.

INTRODUCTION

Bile duct stones are common causes of hepatobiliary surgery and are typically classified into primary bile duct stones and secondary bile duct stones, which develop from gallbladder stones[1]. The main symptoms of common bile duct stones include biliary colic, obstructive jaundice, cholangitis, and pancreatitis[2]. If left untreated, these conditions can lead to more severe complications, potentially progressing to bile duct or pancreatic cancer[3]. For common bile duct stones, endoscopic retrograde cholangiopancreatography (ERCP) is uniquely advantageous for stone removal and is widely recognized as a key method for managing biliary and pancreatic diseases[4]. However, the success of ERCP depends on the skill of the operator because the procedure is associated with a high risk of complications. When the procedure is performed by an endoscopist with insufficient training or experience, the likelihood of postoperative complications increases[5]. Postoperative complications include pancreatitis, bile duct bleeding, infection, and perforation[6]. Studies have shown that the occurrence of related complications is primarily influenced by two factors: The indication for the procedure and the technical skills of the endoscopist[7]. Therefore, simulating the procedure and accumulating relevant experience have always been key objectives in physician training and research.

Previous studies on ERCP training models have primarily focused on in vitro models and computer-based simulations[8-11]. However, a survey revealed that a relatively small fraction of trainees had access to simulation models[12]. Due to rapid advances in three-dimensional (3D) printing technology, these models have been widely used in medical education, including preoperative simulations and undergraduate teaching. The value of 3D-printed models has been demonstrated, as they provide a relatively intuitive and realistic sensory experience[13-15]. This finding suggests that integrating 3D-printed models into ERCP training could lead to increased access to simulation models, enhancing both training efficiency and realism. Therefore, we aimed to develop a comprehensive ERCP surgical model using 3D printing technology that is convenient, user-friendly, and reusable to support the education of young doctors.

MATERIALS AND METHODS

Ethics statement

This study was approved by the Ethics Committee of Guangdong Second People’s Hospital (No. 2024-KY-KZ-391-01) and complied with the Helsinki Declaration. The participants provided informed consent and agreed to be published, allowing the use of all the data collected for scientific research only.

Construction and printing of 3D models

To create a more realistic ERCP simulation model, a partnership was established with a 3D printing company. Computed tomography (CT) data from patients who had undergone ERCP procedures were retrospectively collected and provided to the collaborator, Tengwei Technology (Guangzhou, Guangdong Province, China), for the production of a 3D-printed soft model of the esophagus, stomach, duodenum, and common bile duct (Figure 1A and B). As shown in Figure 1C, a magnetic device was used to divide the entire model into three parts at the duodenal papilla: The esophagus, stomach, duodenum, and common bile duct; and the connection to the papilla. The assembled model is shown in Figure 1D. The model was hollowed out to allow the passage of the duodenoscope. Four fixation points were designated at the duodenal papilla connection site and transparent dressings were used to simulate the surgically incised duodenal papilla. The detachable magnetic design facilitates easy replacement of the transparent dressing, enabling repeated practice. Additionally, clay and straw were used to fill the common bile duct, simulating the selection and insertion of the guide wire. By adjusting the straw position, different bile duct shapes were modeled. The entire model was constructed of translucent silicone, allowing for clear observation of the duodenoscope position during the procedure, which aids in simulation practice for junior doctors.

Figure 1 Construction of a three-dimensional-printed model based on computed tomography data. A: Computed tomography scan data of endoscopic retrograde cholangiopancreatography patients before surgery; B: Construction of the three-dimensional (3D) simulation model; C: Division of the model into the gastroduodenal, common bile duct, and duodenal connection sections; D: 3D-printed model after reconstruction; E and F: Design of the duodenal papilla connection section.

Design of the duodenal papilla

The detachable magnetic design of the duodenal papilla not only allows for the model to be reused but also allows for modification of spatial relationships between the clay and the straw to simulate various common bile duct shapes encountered in practice. Additionally, by adjusting the placement angle and direction of the straw, different levels of difficulty could be created (Figure 1E and F).

The pancreatic and bile duct junction represents the point at which the bile duct and pancreatic duct merge before entering the duodenum and is typically located in the descending part of the duodenum. The normal openings of the pancreatic and bile ducts at the duodenal papilla are generally classified into three types: (1) The common bile duct and main pancreatic duct are completely separate and individually open into the duodenum; (2) The common bile duct and main pancreatic duct are parallel with no common channel, but open into the duodenal papilla together; and (3) The common bile duct and main pancreatic duct merge to form the ampulla of Vater, which then opens into the duodenal papilla. Based on the different classifications of the pancreatic and bile duct junction, various components were designed for the openings of the common bile duct and pancreatic duct, adapting them to different scenarios through repeated practice.

Simulation of key ERCP procedure steps

To obtain evidence of preliminary validity, two senior endoscopists independently evaluated the simulator using a structured questionnaire based on a 5-point Likert scale (1 = very poor, 5 = excellent). The results showed that the simulator adequately reproduced key ERCP steps and the endoscopists considered it a useful adjunct to early-stage ERCP training. These findings provide preliminary evidence of face and content validity for the model (Table 1). As shown in Figure 2, the duodenoscope was inserted through the esophagus, and after an appropriate amount of paraffin oil was applied, the endoscope was successfully advanced into the duodenum. The duodenal papilla was identified via the lens, and a guidewire was inserted. Following confirmation that the guidewire had entered the common bile duct, the papilla was carefully incised with a duodenotomy knife, and a stone removal basket was introduced. To minimize the risk of repeated radiation exposure and to enhance procedure portability, direct visualization and common bile duct lithotomy was applied. The stones were then removed from the duodenal opening using a basket.

Figure 2 Simulation of the endoscopic retrograde cholangiopancreatography surgical process. Comparison of practical (top) and model operation (bottom). From left to right: Duodenal papilla identification; Guidewire insertion; Papillary incision; Stone basket insertion; Stone extraction.

Table 1 Model effectiveness evaluation.

Domain	Observed average
Physical attributes
Anatomical landmark visibility	4.25
Model organ size accuracy	4.3
Authenticity of materials	4.4
Overall impression of the model	4.35
Realism of experience
The force required to move the duodenoscope within the model	4.6
The force required to insert the guidewire	4.35
Authenticity of the duodenal papilla	4.2
Rate your ability to perform the below tasks on the simulator
Using a duodenoscope to locate the papilla	4.1
Guidewire placement catheter	4.5
Nipple incision	4.3
Insertion of stone extraction basket	4.3
Basket stone extraction	4.15
Rate the value of the simulator
Evaluating the value of simulators as training tools	4.4
Evaluating the value of simulators as teaching tools	4.6
Rate the simulator’s relevance to your real-world operations	4.45

Ratings from two senior doctors. Full score for each item: 5 points.

Use of models in training junior doctors

To help junior doctors better understand bile duct stone diagnosis and treatment, as well as the key techniques involved in ERCP, 3D-printed models can be used for teaching purposes. Additionally, questionnaire surveys were deployed to explore the role of these models in the learning process. The pedagogical framework used in this study is illustrated in Figure 3. The goal was to assess junior doctors’ understanding of cholelithiasis and ERCP from six key perspectives: Biliary anatomy, theoretical knowledge, patient management, complication management, procedural steps, and self-confidence. On the basis of this framework, two sets of questionnaires were designed: One objective and one subjective. The objective questionnaire covered theoretical knowledge, including bile duct anatomy, perioperative patient management in ERCP, and bile duct stone management. The subjective evaluation questionnaire focused on junior doctors’ self-assessment of their understanding of bile duct stone patients and surgical techniques. After scores were standardized according to the scoring system, the final score reflected junior doctors’ mastery of the relevant knowledge. The questionnaire is in the Supplementary material.

Figure 3 Diagram of the teaching model. 3D: Three-dimensional.

Thirty young doctors were recruited from the hepatobiliary surgery training program and their basic information was collected, including their sex, age, and education level. All participating doctors met the following criteria: (1) Strong communication and comprehension skills; (2) Regular attendance; (3) No failing grades in prior examinations; and (4) The ability to complete assigned learning tasks conscientiously. Owing to the exploratory and pilot nature of this single-center educational study, no formal a priori sample size calculation was performed. The sample size (n = 30) was determined based on the number of eligible junior doctors available during the study period and the logistical feasibility of simulator training sessions. The doctors were randomly assigned to one of the two groups, each consisting of 15 participants. Prior to the teaching session, they were asked to review materials on bile duct stones and complete two questionnaires. Senior hepatobiliary surgeons were invited to deliver lectures concerning the etiology, anatomy, clinical manifestations, and surgical methods of bile duct stones. The focus was on explaining the precautions before, during, and after ERCP, as well as guiding the students through real case analyses and teaching rounds. In the experimental group, 3D-printed models were introduced to enhance understanding.

To improve the proficiency of young doctors in ERCP, the control group primarily learned about the ERCP process through surgical videos, with the instructor analyzing each step. The experimental group used 3D-printed models for hands-on simulation. Each doctor in the experimental group had the opportunity to practice with duodenoscopes and 3D-printed models under the guidance of instructors. After the session, both groups completed the same questionnaires again, and the results were compared to assess their understanding of the teaching content. To ensure comparability between the two groups, the total duration of structured teaching was standardized to 4 hours for both groups. All participants first received 1 hour of theoretical instruction and 1 hour of standardized surgical video instruction. The remaining 2 hours differed between groups: The control group engaged in instructor-led discussion and step-by-step video review, whereas the experimental group participated in supervised hands-on simulator practice using the 3D-printed model. Thus, although the content of the final session differed, the total instructional time and faculty contact time were equivalent between groups.

Statistical analysis

Statistical analysis was performed using SPSS 26.0. The normality of continuous variables was assessed using the Shapiro-Wilk test. Normally distributed variables are presented as the mean ± SD and were compared using independent-samples t tests. Non-normally distributed data were analyzed using the Mann-Whitney U test. Given the relatively small sample size (n = 15 per group), small-sample bias-corrected standardized effect sizes (Hedges’ g) were calculated for between-group comparisons. Effect sizes were interpreted as small (0.2), moderate (0.5), or large (≥ 0.8). Because multiple questionnaire domains were analyzed, P values were interpreted cautiously, and emphasis was placed on effect sizes and overall consistency of findings rather than isolated statistical significance. A two-sided P < 0.05 was considered statistically significant.

RESULTS

We compared the basic information of the 30 young doctors. As shown in Table 2, there were no significant differences between the two groups in terms of sex, age, education level, duration of exposure during hepatobiliary surgery, prior experience using models for endoscopy exercises, or pre-teaching scores (P > 0.05). Most of the young doctors reported having had little or no exposure to 3D-printed models and had limited knowledge of bile duct stone diagnosis, treatment, and ERCP procedures. After the second questionnaire was completed, all indicators significantly improved after teaching, regardless of the teaching method (Table 3), demonstrating the effectiveness of the teaching method. While all questionnaire scores improved after the session, there was no statistically significant difference between the experimental and control groups in terms of theoretical scores on the objective test questionnaire (70.0 ± 7.9 vs 71.0 ± 6.3, P = 0.614). However, compared with the control group, the experimental group showed statistically significant improvements in the understanding of biliary anatomy (8.1 ± 0.5 vs 6.4 ± 0.5, P < 0.001), patient management (7.5 ± 0.5 vs 7.1 ± 0.5, P = 0.04), complication management (7.1 ± 0.4 vs 6.7 ± 0.5, P = 0.036), procedural steps (7.3 ± 0.8 vs 5.7 ± 0.4, P < 0.001), and self-confidence (7.3 ± 0.2 vs 6.9 ± 0.6, P = 0.012). Small-sample bias-corrected effect sizes (Hedges’ g) demonstrated large to very large between-group differences for several subjective effects. Although the effect sizes for biliary anatomy and procedural steps were numerically large, these values should be interpreted in the context of the relatively small within-group standard deviations and the limited scoring range of the Likert-scale questionnaire. These results indicate that model-based teaching has advantages over purely theoretical instruction.

Table 2 Baseline characteristics of participants, mean ± SD.

Variables	General teaching (n = 15)	Model teaching (n = 15)	χ2 value	P value
Sex, male/female	12/3	13/2	0.475	0.638
Age (year)	26.4 ± 2.0	26.6 ± 1.7	-0.297	0.769
Education level (undergraduate/master/PhD)	10/5/0	10/4/1	-0.323	0.749
Time spent in hepatobiliary surgery (year)	2.1 ± 0.7	1.7 ± 0.8	1.213	0.235
Time spent in endoscopy (year)	0.2 ± 0.4	0.1 ± 0.4	0.475	0.07
Pre-teaching theoretical performance	41.3 ± 9.9	40.0 ± 8.2	0.401	0.692
Pre-teaching understanding of biliary anatomy	2.3 ± 0.7	2.2 ± 0.6	0.462	0.647
Pre-teaching patient management	2.0 ± 0.5	2.0 ± 0.3	0.182	0.857
Pre-teaching understanding of complications	2.1 ± 0.5	2.3 ± 0.6	-1.148	0.261
Pre-teaching procedural steps	1.5 ± 0.3	1.7 ± 0.3	-1.855	0.07
Pre-teaching confidence	1.7 ± 0.3	1.8 ± 0.3	-0.915	0.368

Table 3 Post-teaching outcomes and standardized effect sizes, mean ± SD.

Outcome	General teaching (n = 15)	Model teaching (n = 15)	P value	Hedges’ g
Theoretical performance	71.0 ± 6.3	70.0 ± 7.9	0.614	-0.13
Understanding of biliary anatomy	6.4 ± 0.5	8.1 ± 0.5	< 0.0011	-3.31
Patient management	7.1 ± 0.5	7.5 ± 0.5	0.0401	0.78
Understanding of complications	6.7 ± 0.5	7.1 ± 0.4	0.0361	0.86
Procedural steps	5.7 ± 0.4	7.3 ± 0.8	< 0.0011	2.46
Confidence	6.9 ± 0.6	7.3 ± 0.2	0.0121	0.87

¹Significant difference.

Hedges’ g represents small-sample bias corrected standardized mean differences. Effect size interpretation: Small (0.2), moderate (0.5), large (≥ 0.8).

DISCUSSION

Bile duct stones commonly develop in the digestive system at an incidence rate of approximately 18% in the general population[16]. In accordance with the relevant guidelines and owing to the potential health complications they cause, patients diagnosed with common bile duct stones are recommended to undergo lithotomy whenever possible[17]. Over the years, significant progress has been made in the treatment of bile duct stones. Currently, common surgical methods include laparoscopic common bile duct exploration, laparoscopic transcystic common bile duct exploration, and ERCP. Compared with laparoscopic surgery, ERCP is favored because of its minimal invasiveness, significant efficacy, and association with faster recovery times. However, most young doctors lack opportunities to simulate the ERCP procedure, and improper technique can lead to serious complications, including perforation and bleeding. Studies on the ERCP learning curve suggest that trainees typically need to perform approximately 255 procedures to achieve competency in routine biliary ERCP[18]. Beginners cannot experience the sensations of intubation and biliary sphincterotomy in real patients and therefore must engage in continuous simulation practice to gain hands-on experience. Traditionally, ERCP training models can be categorized into four types: Mechanical, in vitro, hybrid, and digital[19]. In vitro animal models are difficult to establish and require expensive consumables. Digital models lack tactile feedback, and mechanical models still require further development to improve their simulation accuracy. Therefore, compared with previously reported ERCP simulators, including ex vivo biological models and dry mechanical simulators, our model emphasizes reusability, modular design, and portability. While some previously published models provide fluoroscopic simulation or higher anatomical fidelity, they often require complex setups or costly consumables. Our design prioritizes accessibility and repeated practice in resource-limited teaching settings. However, further studies evaluating the construct validity and skill transfer to clinical performance are necessary to fully establish its educational effectiveness.

In recent years, 3D-printed models have revolutionized the medical field because of their ability to improve surgical success rates, portability, and usefulness in simulating clinical procedures. They have been widely applied in orthopedics, urology, hepatobiliary surgery, dentistry, and other areas, particularly in preoperative simulations[20-22]. Yao et al[23] divided 62 patients who underwent laparoscopic liver resection into two groups: A 3D model-guided group and a traditional enhanced CT or magnetic resonance imaging-guided group, with 31 patients in each group. The results revealed that the 3D model group had a lower incidence of intraoperative bleeding and fewer major complications 30 days after surgery. Multivariate analysis indicated that use of the 3D model was an independent protective factor associated with a reduced incidence of postoperative complications. Zhang et al[24] used a 3D-printed liver tumor model for preoperative in vitro positioning, guiding ultrasonic microwave ablation of liver tumors. This approach reduced the number of repeated punctures and improved the accuracy and safety of percutaneous microwave ablation of the liver. Building on these advances, we aimed to use 3D printing technology to create personalized ERCP models for preoperative simulations. However, due to the lengthy printing process, it is not feasible to complete the model before the patient undergoes surgery. As a result, we opted to use the models for practice and teaching purposes, allowing young doctors the opportunity to simulate the ERCP process. This gap remains a limitation. In a recent study, Lu et al[25] combined stereolithography 3D printing with self-healing materials that mimic the liver-like modulus. Using 4-acryloylmorpholine and methoxy polyacrylate, they were able to quickly create a liver model with self-healing properties, offering new insights into reducing model construction time by using better materials.

In this study, we aimed to enhance the realism of our ERCP training model by using CT data from real patients. We constructed a 3D-printed model that included the esophagus, stomach, duodenum, and common bile duct. However, during this process, we identified several challenges that need to be addressed. First, the silicone model lacked the softness and flexibility of human organs. To reduce discrepancies between the model and real organs, we adjusted the model’s curvature by enlarging and reducing certain areas, ensuring that the duodenoscope could pass through smoothly. The second challenge was the reusability of the model. 3D printing is expensive, and the printing process is time-consuming, making repeated use impractical. To overcome this challenge, we designed a modular model with detachable parts. The main sections of the model (the stomach and duodenum) were created as one piece, whereas the common bile duct was a separate component. The duodenal papilla served as a removable connection point. We also used readily available materials such as straws, transparent films, and clay as consumables. Clay and straws were used to simulate guidewire insertion, whereas transparent film was used to simulate surgical incisions. With this design, the trainees could easily replace the consumable parts between practice sessions, allowing for multiple uses. Additionally, if different bile duct shapes need to be simulated, the clay components could be swapped out quickly, making the model highly adaptable. The third challenge was portability and operability. Typically, the ERCP procedure requires the use of contrast agents for bile duct visualization, as well as radiation to locate stones. This approach not only restricts the operating environment to specialized ERCP rooms but also necessitates protective measures such as lead suits. To mitigate the need for radiation and a complex setup, we simplified the stone removal process. We designed the bile duct to be translucent, allowing the trainees to visualize the location of the stones directly without the use of contrast agents. After placing the stone removal basket, the trainees could directly observe the position of the stones and perform the removal procedure. These improvements made the model more practical for repeated use in training settings, allowing the young doctors to simulate ERCP procedures in a safer and more cost-effective manner.

Additionally, we explored the role of the model in teaching young doctors. The first questionnaire revealed that most young doctors, even those specializing in hepatobiliary surgery, had limited knowledge of ERCP and had never used a duodenoscope to complete the procedure. When we compared the two teaching groups, we found no significant difference in improvement in theoretical knowledge. However, the key advantage of using a 3D-printed model is that it allows young doctors to visualize abstract anatomical structures, thereby enhancing their understanding of biliary diseases. By rendering anatomical structures in tangible 3D form, 3D models minimize the cognitive effort required for spatial visualization, thereby enhancing structural comprehension and procedural clarity. Furthermore, the inclusion of the model enriched the classroom experience, improving student engagement and focus. Practical demonstrations and hands-on training with the model improved engagement in the classroom, and therefore, teaching effectiveness. The 3D-printed models simulate realistic clinical scenarios, enabling learners to acquire knowledge through hands-on engagement in authentic contexts. The questionnaire survey also revealed a significant increase in the confidence levels of the students in the 3D printing group, suggesting that they would approach future clinical work with greater composure when managing patients. Nevertheless, several methodological considerations warrant caution. Although the total instructional time was standardized across groups, the experimental group received additional hands-on simulator exposure during the final session, whereas the control group participated in guided video-based discussion. Therefore, it remains possible that part of the observed benefit was attributable to increased active practice rather than the intrinsic value of the 3D-printed model itself. Future studies should consider incorporating a control group with equivalent hands-on exposure using alternative simulation tools to isolate the specific educational contribution of the 3D-printed model.

Despite these advantages, our study has several limitations. First, as mentioned above, we simplified the stone removal process and omitted the use of fluoroscopic guidance, meaning that the ERCP procedure could not be fully replicated. Second, all the participants were recruited from a single institution, which may limit the external validity of the findings and introduce potential selection bias. Moreover, the relatively small sample size may have constrained the statistical power to detect modest between-group differences, thereby increasing the likelihood of type II error. The magnitude of some of the observed effect sizes should also be interpreted with caution. Extremely large standardized differences may partially reflect the restricted variability of questionnaire scores and the bounded characteristics of Likert-scale measurements. In small educational cohorts, reduced within-group dispersion can exaggerate standardized mean differences. Consequently, the present findings should be viewed as preliminary evidence of improved perceived understanding rather than conclusive evidence of marked educational superiority. To assess the role of 3D-printed models, the sample size should be expanded, participants from multiple hospitals should be included, and the long-term progress of young doctors should be periodically reassessed. Although questionnaire-based knowledge scores and confidence levels are commonly used endpoints in educational research, they cannot fully substitute for objective measures of technical competence, such as cannulation success rate, procedure duration, structured skill assessment scores, or complication rates. Future studies should incorporate validated technical performance assessment tools to provide more robust evidence regarding the simulator’s impact on clinical competence.

In the future, we aim to explore ways to shorten the time needed to construct a 3D-printed model; thus, if the time can be effectively shortened, more preoperative simulations can be performed, potentially reducing the incidence of postoperative complications. Additionally, we plan to include more complex biliary conditions in our models, such as stenosis and tumors, to simulate procedures for a wider range of biliary diseases. Furthermore, by upgrading the printing materials and methods, both the realism of the model and the operational flexibility have been improved. Lastly, our models are not limited to ERCP; they can also be applied in SpyGlass procedures and other endoscopic practices.

CONCLUSION

In summary, we developed a silicone-based soft model for ERCP practice that offers young doctors the opportunity for repeated training through the simple replacement of materials. The model is both portable and realistic, providing an effective platform for hands-on learning. Our findings suggest that compared with traditional learning methods, model-based training may enhance understanding of key procedural concepts and improve self-reported confidence. However, given the questionnaire-based design and modest sample size, further studies incorporating objective performance assessments are needed to determine its impact on actual clinical ERCP competence.