Development and validation of a realistic neonatal intestinal atresia simulator for the training of pediatric surgeons

doi:10.21203/rs.3.rs-4008391/v1

Background

Neonatal surgical pathology presents high technical complexity and few opportunities for training. Many of the neonatal surgical entities are not replicable in animal models. The use of realistic 3D models is a cost-effective and efficient alternative for the training of new generations of pediatric surgeons.

Methods

We conceptualized, designed, and produced an anatomically realistic model for the open correction of jejunoileal atresia. We validated it with two groups of participants (experts and non-experts) through face, construct, and content validity questionnaires.

Results

The model was validated by 11 experts and 9 non-experts. The mean procedure time for the experts and non-experts groups was 41 and 42 minutes respectively. Six non-experts and one expert did not complete the procedure at the designed time (45 minutes) (p = 0.02). The mean score of face validity was 3.1 out of 4. Regarding construct validity, we found statistically significant differences between groups for the correct calculation of the section length of the antimesenteric border (Nixon's technique) (p < 0.01). Concerning content validity, the mean score was 3.3 out of 4 in the experts group and 3.4 out of 4 in the non-experts group.

Conclusions

The present model is a realistic and low-cost valid option for the training of open correction of jejunoileal atresia. Future studies with larger sample sizes and blinded validators are needed before drawing definitive conclusions.

Pediatrics

Surgery

intestinal atresia

jejunoileal atresia

simulation

silicone

3D

paediatric surgery

training

model

open surgery

The training of new generations of Paediatric Surgeons is strongly conditioned by their possibility to acquire and train the technical competencies and skills inherent to the specialty. While in many basic pathologies, the available volume is high and the learning curve is simple, in other scenarios the training and learning possibilities are conditioned by the low prevalence of the diseases.

Neonatal surgery, a major part of the specialty, is a clear example of the above. Low birth rates, an aging population, fertility problems, and marked improvements in prenatal diagnostic tools have led to a sharp decline in the volume of neonatal surgical pathology in Europe [1–3]. Also, the trend towards the use of minimally invasive techniques (such as thoracoscopy in oesophageal atresia) [4–6] and the tendency of centralizing cases in referral hospitals [7–8] exacerbates the problem.

Given this situation, several options have been put forward to train new generations of pediatric surgeons: 1) The use of animal models [9–11]. Although they have the great advantage of tissue realism and the physiological and homeostatic conditions of a mammal, they are expensive. Apart from that, many of the entities are not replicable in animal models because of their intrinsic characteristics (e.g. jejunoileal atresia, where there is a marked discordance in caliber between the intestinal ends, a situation that is not easy to replicate realistically in animal models). 2) The use of cadavers [12], which involves low availability, a high preparation cost, and a significant bioethical conflict, is not an acceptable resource for everyone. 3) The use of simulation models, built with different synthetic materials [13–15]. The marked industrialization and technological progression we are experiencing are contributing to lowering the design and production costs of these models and making their generalization for the training of Paediatric Surgeons possible. The biggest handicap of these models is, in many cases, the lack of realism. To the best of our knowledge, there is only one precedent in the literature regarding synthetic intestinal atresia models for the training of pediatric surgeons [16]. The present work aims to design, produce, and validate a low-cost and anatomically realistic model of neonatal jejunoileal atresia for the training of open corrective surgery by Paediatric Surgeons.

Conceptualization and preliminary design of the model

For the initial design, necropsic, surgical, and prenatal radiological references of the small bowel (normal, dilated/obstructed, and obliterated/dysfunctionalised) were taken [16–19], and a preliminary range of measures and diameters was established. Autodesk Fusion 360 ® (Autodesk, CA., USA) was used to design the first composition of the model and to establish an approximate proportional relationship between the two intestinal segments. Iterative adjustments and refinements were performed to ensure the model's fidelity to neonatal bowel characteristics

Model production methodology

The simulator comprises an anatomical model of jejunoileal atresia with discordant ends and a vascularized mesentery. The model is supported by a specially designed stand for proper usage.

To simulate the mucosa inside the intestine, platinum silicone Eco-Flex 0030 (Smooth-On) with red dye and Silicone Thinner (Smooth-On) additive in a 1A:1B:0.2C ratio were used. The mixture was injected into 3D-printed PLA molds using a Prusa MK3S 3D printer (Prusa Research, Prague, Czech Republic). After a 4-hour curing period, the molded cylinder representing atresia was covered with a slightly larger mold to create the serosa layer. This serosa layer, composed of 15g of Eco-Flex 0030 with a rosy pigment, was cured and introduced into a third mold to add the mesentery to the model. The mesentery was created using 5g of Eco-Flex 0030 with a red pigment. An arbitrary arboriform vascular pattern was reproduced to simulate real vasculature. Finally, the model was coated with Silicone Thinner, an oily coating, to provide a more realistic experience. A custom-designed stand was manufactured to secure the model, allowing adjustment of rotation and tension without requiring external assistance.

The final version of the model

This model constitutes a low-cost and anatomically realistic representation of neonatal jejunoileal atresia with discordant ends placed on a stand for optimal surgical technique positioning. The proximal intestinal segment (dilated) measures 12 cm in length and has a luminal diameter of 20 mm. It is composed of two platinum silicone layers of different hardness. The inner layer simulates the mucosal-muscular tissue and is 0.8 mm thick, while the outer layer simulates the serosa, is 0.3 mm thick, and is made of stiffer silicone. The distal intestinal segment (atretic) measures 12 cm in length and has a luminal diameter of 8 mm. It replicates the same layers and thicknesses of the proximal intestinal segment end. The simulator also includes a vascularized mesentery made of a thin silicone sheet, which facilitates training in vascular control and bowel sectioning skills specific to this type of intervention.

The complete model's production time is 4 hours. The replacement parts (silicone) production time takes 3.5 hours. The production cost, including materials, labor, and indirect costs (electricity consumption), is 45 € for the complete model (including the stand) and 25.21 € for the model without the stand. This price is estimated for individual handmade production. An industrialized production process would lead to lower costs and greater uniformity, making the product more competitive.

Validation

A validation protocol was carried out using two groups of validators: experts (group 1) and non-experts (group 2). Group 1 comprised consultant Paediatric Surgeons who had performed the procedure on at least one previous occasion. Group 2 consisted of General Surgery or Paediatric Surgery residents in their second to fifth year of training, with basic surgical skills but no specific training in neonatal surgical pathology or the surgical management of intestinal atresia.

Validation was conducted through a two-stage process. 1) First, an instructional video was presented to demonstrate the surgical procedure to be performed using the model (Supplementary Material 1). 2) Second, the procedure was performed under the direct visual supervision of 2 team collaborators (OEB and BPR) with continuous recording of the surgical field for reassessment. Participants did not see or manipulate the model before the validation procedure.

Specific questionnaires and checklists were developed to assess content, face, and construct validity. The number of items included in each questionnaire was: content validity: 10 items; face validity: 20 items; construct validity: 21 items. All items were rated on a Likert scale from 1 (strongly disagree) to 4 (strongly agree).

Statistical analysis

Continuous quantitative variables were expressed as mean (standard deviation). For the comparison of these variables, we used the Mann-Whitney U-test. The statistical significance value was set at p = 0.05 (two-tailed). All analyses were carried out in STATA 17.0 (StataCorp, LLC) ®.

Construct validity

The mean procedure time for the experts and non-experts group was 41 (sd = 3.70) and 42 (sd = = 5.15) minutes respectively.

Two team collaborators completed a checklist regarding construct validity questionnaire for all the experts (n = 11) and non-experts (n = 9). We found statistically significant differences in the proportion of participants who "Adequately calculated the section length of the antimesenteric border (Nixon technique)", which was 100% in the expert group and 22.2% in the non-expert group (p = 0.01). Statistically significant differences were also found in the number of validators who completed the procedure within the established time, 90.9% in the expert group (n = 10) and 33% in the non-expert group (n = 3) (p = 0.02). Table 1 shows the comparison between groups for construct validity items.

Face validity

All the experts (n = 11) responded to the face validity questionnaire. The best-rated items were those concerning the simulation of anastomotic congruence techniques (Benson and Nixon) which had an average score of 3.6 out of 4. The worst-rated item was "the model reproduces the surgical dimensions of a neonatal abdominal field.", with a mean score of 2.3 out of 4. The mean score of the face validity questionnaire was 3.1 out of 4 (sd = 0.4) Table 2 shows the mean score of each item in the face validity questionnaire.

Content validity

All the experts (n = 11) and non-experts (n = 9) responded to the content validity questionnaire. In the experts group the best-rated item was: “This model helps the user understand the surgical technique”, with a mean score of 3.9 out of 4. The worst-rated item was: “This model helps the user learn how to handle the neonatal bowel and mesenteric structures in a surgical context” with a mean score of 2.7 out of 4. In the non-experts group, the best-rated items were: “This model allows you to LEARN different surgical techniques”, “This model allows you to TRAIN different surgical techniques” and “This model helps the user to be better prepared when performing corrective surgery for jejunoileal atresia in a neonate for the first time”, with a mean score of 3.6 out of 4. The worst-rated items were: “This model allows to EVALUATE the user's surgical technique” and “This model helps the user understand how intestinal tissue responds to being handled in surgery” with a mean score of 3.1 out of 4. The mean score of the content validity questionnaire was 3.3 out of 4 for the experts (sd = 0.38) and 3.4 out of 4 for the non-experts (sd = 0.18). Table 3 shows the mean score of each item in the content validity questionnaire.

In the present work, we designed, produced, and validated a low-cost and anatomically realistic model of neonatal intestinal atresia with a group of 11 experts and 9 non-experts.

Since literature in this regard is scarce, [16] the most challenging aspect in the design and development of this model was the search for precise references of the anatomical calibers and measures. The participation of pediatric surgeons in this phase was essential. In this regard, the publication of precise anatomical calibers and measures of the different neonatal pathologies may contribute to the development of more realistic models in the future.

The correction of neonatal intestinal atresia requires some specific surgical maneuvers, such as anastomotic congruence techniques. This validation study showed the highest scores in the items related to these maneuvers, demonstrating that this is a valid model for learning and training them.

One of the most outstanding and innovative elements of this model is the mesentery. Although the characteristics of the mesentery obtained a relatively low score in the face validity questionnaire, the construct validity evaluation showed differences between the two groups (i.e. “Ligates the mesenteric vessels without grasping any of them with the forceps”, which showed a proportion of 63.6% in the experts' group and 22.2% in the non-experts' group, p = 0.09). Despite the lack of statistical significance, this difference suggests that the experts had a greater ability to manipulate delicate tissues than non-experts. Mesenteric surgical principles in the neonate are an integral part of the corrective procedure for neonatal intestinal atresia (both because of the tissue delicacy and these patients’ hemodynamic lability,).

Although the current trend is towards the development of minimally invasive surgery (MIS), the experience in intestinal atresia is limited. In this context, it seems important that future specialists acquire the essential surgical skills of open surgery before progressing to MIS. Nevertheless, this model could be introduced in a simulated neonatal abdomen to train the technique of MIS.

Finally, we believe that the intestinal model we have produced (bilayer with differences in the hardness of each layer) allows for multiple types of intestinal suturing (seromuscular, full thickness...) which enriches the user's training experience. We consider this to be a substantial improvement and difference from the existing precedent in the literature published by Takazawa et al. [16].

The construct validity showed interesting differences between groups on key aspects related to the surgical procedure (e.g. "Resects only the essential amount of affected intestine" with 100% in the case of experts and 66.7% in the case of non-experts; p = 0.07) We attribute the lack of statistical significance in those items to the low sample size. The scarcity of pediatric surgeons and their wide geographical dispersion constituted important difficulties for the recruitment of experts.

We believe the use of simulated models in Paediatric Surgery is promising for several reasons: First, because of their low production cost and reproducibility. Animal models, which are expensive and may present some ethical conflicts, have an important variability that may limit training conditions. Second, the required technology is available worldwide, which is particularly important in low-to-middle-income countries. Third, because of the easiness with which an individual practice can be set up.

We acknowledge that the small sample size of both groups represents a major limitation of this study. Furthermore, the use of more complex validation systems (such as pressure sensors or leakage tests) would have provided more objective information. Also, the fact that the team collaborators who completed the construct validity questionnaire were not blinded to the type of participant (expert or non-expert) may have affected the results. On the other hand, the methodological rigor in the design and performance of the validation study represents the main strengths of this work.

In conclusion, this is a low-cost and realistic valid model for the training of neonatal intestinal atresia open surgery. Further studies with larger sample sizes and external validators blinded to the type of participants are needed before drawing definitive conclusions. Because the use of simulators in Paediatric Surgery may contribute to better global care of children, especially neonates, this line of research should become a priority.

CRediT authorship contribution statement:

JAM: Original idea; literature search; model conceptualization and design; study design; data curation and extraction; project administration; resources; writing – original draft; writing – review and editing.

NLC: Model conceptualization and design; model production, project administration; resources; writing – original draft; writing – review and editing.

NMC: Study design; data curation and extraction; formal analysis; project administration; resources; writing – original draft; writing – review and editing.

BPR, OBA: Model production and validation; analysis; resources; writing - original draft; writing - review and editing.

FJP: writing - review and editing.

CONFLICTS OF INTEREST:

The authors declare that they have no conflict of interest.

FINANCIAL STATEMENT/FUNDING:

This review did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. None of the authors have external funding to declare.

ETHICAL APPROVAL:

This project was approved by the Research Ethics Committee of the University of Navarra on 22.12.2022 under code 2022.209

STATEMENT OF AVAILABILITY OF THE DATA USED:

The data used to carry out this study are available upon request from the review authors.

INDUSTRIAL PROPERTY

The present model is under the registration and protection of industrial property under the code U202330721.

ACKNOWLEDGEMENTS:

We would like to express our sincere gratitude to the following people for their altruistic and voluntary participation in the validation of this simulator. Without their feedback and willingness, this project would never have been possible:

Alvira Reyes Delgado
Paolo Bragagnini
Ainara González Esdera
Paulina Vargova
Yurema González Ruiz
Marina González Herrera
Mercedes Ruiz de Temiño Bravo
Carolina Corona Bellostas
Rafael Fernández Atuan
Raquel Ros Briones
Lucas Sabattel
Nuria Blanco
Sara Hernández-Martín
Elena Calleja Aguayo
Carlos Bardají Pascual
Helena Linero González
Iker Rodríguez Laguna
Cristian Fernández Romance
Carmen María Gálvez Estévez
Marina Román Moleón

Funding:

None

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Table 1. Construct validity evaluation.

Item	Experts (n=11)	Non-experts (n=9)	p-value
Decides to ligate the mesenteric vessels before sectioning. (% Yes)	72.7	55.6	0.64
Ligates the mesenteric vessels without tearing them (% Yes)	45.5	22.2	0.37
Ligates the mesenteric vessels without grasping any of them with the forceps (% Yes)	63.6	22.2	0.09
Does not produce damage to mesenteric vessels during the whole process (% Yes)	72.7	44.4	0.36
Correctly identifies the mesenteric section area and vascular boundaries of the intestinal segment to be resected (% Yes)	81.8	77.8	0.99
Sections bowel accurately, without deviation (% Yes)	81.8	33.3	0.07
Resects only the essential amount of affected intestine (<2 cm from the beginning of the healthy intestine in each segment) (% Yes)	100	66.7	0.07
Adequately spatulates intestinal loop (Benson technique) (% Yes)	72.7	33.3	0.18
Adequately calculates the section length of the antimesenteric border (Nixon technique) (% Yes)	100	22.2	0.01
Start anastomosis with side sutures and references them (% Yes)	90.0	100	0.99
In general, sutures are seromuscular (% Yes)	100	88.9	0.45
Sutures are generally equidistant from each other (% Yes)	100	88.9	0.45
In general, the entry points of the suture in relation to the free margin are equidistant (% Yes)	100	88.9	0.45
In general, hand-made knots are performed correctly (“surgeon´s knot”) (% Yes)	100	100	0.99
In general, knots are performed correctly using the Mayo holder (% Yes)	100	100	0.99
Does not leave overlapping anastomotic edges (% Yes)	36.4	22.2	0.64
Does not tear serosa (% Yes)	45.5	66.7	0.41
Properly repositions lateral references before intestinal rotation (% Yes)	81.8	66.7	0.62
Adequately rotates the anastomosis without damaging the mesentery or the bowel (% Yes)	63.6	44.4	0.65
Number of sutures employed (average)	3	2.7	0.25
Completes procedure in < 45 minutes (% Yes)	90.9	33.3	0.02
Average time to complete the procedure (only takes into account those who completed the procedure) (minutes)	41 (3.70) (n=10)	42 (5.15) (n=3)	0.61

Table 2. Face validity questionnaire.

Item	Mean score (experts) N=11
The intestinal diameter of the model resembles that of neonatal intestinal atresia.	2.7
The intestinal thickness of the model resembles that of neonatal intestinal atresia.	3.0
The mesentery resembles that of a real neonatal intestine.	2.4
Mesentery vessels are adequately represented	3.2
The layers of the model realistically simulate a real neonatal intestine.	3.4
Visually, the model material resembles a real neonatal intestine.	3.5
The feel of the model (wet and slippery) resembles a real neonatal intestine.	2.8
The texture and consistency of the model when the suture needle passes through it is similar to that of a real neonatal intestine.	3.3
The sensation of suturing the model's strands together is similar to that of a real neonatal intestine.	3.1
The model reproduces the surgical dimensions of a neonatal abdominal field.	2.3
The spatial positioning of the model resembles that of a surgical field.	2.5
The model allows a mobility of the structures similar to reality.	2.9
In general, the execution of the surgical technique for the correction of a neonatal intestinal atresia on the model resembles reality	3.0
This model is USEFUL for LEARNING the surgical technique for the correction of intestinal atresia.	3.6
This model is USEFUL for TRAINING surgical technique for the correction of intestinal atresia.	3.5
This model allows realistic simulation of the Benson anastomotic congruency technique (spatulation of the distal anastomotic end).	3.6
This model allows realistic simulation of Nixon's anastomotic congruence technique (longitudinal opening of the antimesenteric edge of the distal anastomotic end).	3.6
This model allows a realistic simulation of an end-to-end intestinal anastomosis with discordant calibre ends.	3.5
This model allows the acquisition of surgical skills transferable to the real surgical field.	3.5
This model realistically reproduces the level of difficulty of the procedure.	3.1
MEAN SCORE	3.1

Each item was evaluated on a 4-point Likert scale (1: totally disagree - 4: totally agree)

Table 3. Content validity questionnaire.

Item	Mean score (experts) N=11	Mean score (non-experts) N=9	p-value
This model helps the user to understand the surgical technique.	3.9	3.4	0.17
This model helps the user to understand the spatial arrangement of the intestine and mesentery in a neonate.	3.3	3.4	0.74
This model helps the user to learn how to handle the neonatal bowel and mesenteric structures in a surgical context.	2.7	3.2	0.33
This model helps the user understand how intestinal tissue responds to being handled in surgery.	3.0	3.1	0.74
This model allows you to LEARN different surgical techniques	3.6	3.6	0.88
This model allows TRAINING different surgical techniques	3.5	3.6	0.84
This model allows to EVALUATE the user's surgical technique.	2.9	3.1	0.56
This model allows the user to measure their ability to perform corrective surgery for neonatal intestinal atresia.	3.1	3.2	0.67
This model helps the user to be better prepared when performing corrective surgery for intestinal atresia in a neonate for the first time.	3.5	3.6	0.93
This model serves to increase the user's confidence before performing corrective surgery for intestinal atresia in a neonate.	3.5	3.4	0.59
MEAN SCORE	3.3 (0.38)	3.4 (0.18)	0.74

Each item was evaluated on a 4-point Likert scale (1: totally disagree - 4: totally agree)

Supplementary Material 1 is not available with this version.

Supplementary material 1: Video demonstration of the surgical correction of neonatal intestinal atresia in the model.

The authors declare no competing interests.

Development and validation of a realistic neonatal intestinal atresia simulator for the training of pediatric surgeons

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Figures

Introduction

Methods

Conceptualization and preliminary design of the model

Model production methodology

The final version of the model

Validation

Statistical analysis

Results

Construct validity

Face validity

Content validity

Discussion

Declarations

References

Tables

Supplementary Material

Additional Declarations

Status:

Version 1