Participants and design
This study was conducted among surgical residents and expert surgeons in order to assess the open inguinal hernia repair simulation model. The surgical residents were invited for inclusion during the education days of the Dutch Association of Surgery. The surgical residents were shown a video-demonstration of the LOIHR with the placement of a tension-free mesh on the model first. Afterward, the surgical residents performed the surgery themselves on the model and filled out the rating scale questionnaires. Participation was anonymous and voluntary. This study does not require institutional board review according to Dutch law.
The international expert surgeons had significant experience in performing the LOIHR. Ten expert surgeons were invited per email for participation. All experts confirmed participation. After confirmation of participation, they were sent a package containing a LOIHR simulation model and an instruction letter including their login credentials to a website where they could view the video-demonstration of the LOIHR performed on the simulation model and where they could fill out the rating scales concerning the model. First, they were asked to view the video-demonstration, then to perform the surgery themselves, and last to fill out the rating scales. Informed consent was obtained from all individual participants included in the study.
Lichtenstein open inguinal hernia repair simulation model
The LOIHR simulation model mimicked the human male groin region, including the abdominal wall layers and the contents of the inguinal canal. Each structure included in the model was crucial for the LOIHR. Positioned within the correct layers were the hazardous structures, such as the superficial epigastric vessels, the spermatic cord, and the ilioinguinal, iliohypogastric nerves and genital branch of the genitofemoral nerve (Fig. 1).
The model was constructed using low-cost materials. The tan-colored fabric was used to mimic the skin, white felt to mimic Scarpa’s fascia, and yellow felt layers to mimic the subcutaneous fat, and red felt was used to mimic the internal oblique muscle. A broad white braided elastic band mimicked the conjoint tendon. White cotton layers were used to represent the anterior rectus sheath and the external oblique aponeurosis, including an opening to simulate the external ring of the inguinal canal and a fold representing the inguinal ligament. The spermatic cord was constructed using batting. Within this batting, a small transparent plastic bag was added to simulate an indirect hernia. Red, blue, yellow, and white yarn were used to mimic the arteries, veins, nerves, and the vas deferens, respectively. The material cost per model was less than five US dollars. This model was identical to the one used for the video-demonstration.
The model was first developed at the Mayo Clinic and was initially reported by Rowse et al. . After using the initial model for training of surgical residents in the Mayo Clinic and Ghana and critical assessment of the model by the senior authors, adjustments were made to optimize the model. Due to the adjustments, the conjoint tendon and a separate anterior rectus sheath were added to the model. The spermatic cord was pasted to the conjoint tendon to allow trainees to dissect it. Finally, the iliohypogastric nerve was adjusted so it would run towards the subcutaneous fat tissue underlying the skin.
The video-demonstration showing the LOIHR on the simulation model lasted for 8:00 min (video-demonstration LOIHR available online). The surgery was based on the description of Amid  and was divided into steps using the step-by-step framework  (Appendix A). The step-by-step framework breaks down surgical procedures based on anatomical structures and implants, into steps and substeps.
After the surgical residents and surgeons operated on the simulation model, they were instructed to fill out the rating scales. The questions were adapted from a previously used questionnaire in a study on fidelity and its different domains using 6 model, 3 equipment, and 4 psychological statements  (Appendix B). An example of a model-related statement was “This simulation model provides a realistic representation of the abdominal layers.” The equipment fidelity was assessed using statements as “On this simulation model, I could demonstrate the precise movements of the open inguinal hernia repair.” Statements as “My experience with the simulation model seemed (overall) consistent with my real-world experiences” were used to assess the psychological fidelity.
The usefulness of the model as a teaching entity and for specific groups (medical students, residents, surgeons) was assessed using six statements (Appendix C). All statements were rated on a five-point Likert scale (1 = Strongly disagree, 2 = Disagree, 3 = Neutral, 4 = Agree, 5 = Strongly agree).
All statistical analyses were performed using SPSS (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 24.0. Armonk, NY: IBM Corp.). Descriptive data were presented as medians and interquartile range (IQR) of the statements per domain of fidelity and for the usefulness were calculated. The Mann Whitney U test was used to compare the surgical residents and expert surgeons. One-sample Wilcoxon signed-rank test was used to compare the median per domain of fidelity and usefulness to the neutral value of 3. The internal consistencies for the three domains within fidelity and for the usefulness rating scales were determined using Cronbach’s α. p values of less than 0.05 will be considered statistically significant.