External validation of a low fidelity drylab platform to enhance loupes surgical skills techniques for hypospadias repair

Summary

Introduction

Hypospadias repair is an index pediatric urology procedure that requires trainee familiarity with surgical loupes. A previous low-fidelity, 6-step curriculum was proposed that deconstructed the most important steps of loupe surgery. We expanded on this curriculum with an intermediate-fidelity silicone hypospadias model and designed an abbreviated version of the 6-step curriculum to precede the hypospadias repair simulation.

Objective

To assess the validity of our prior, low-fidelity conceptual model using the metric of improved performance on the intermediate-fidelity silicone hypospadias model.

Study design

A silicone model was first prototyped with the design software Solidworks^™, and then fabricated using a cast made of a mixture of silicone rubbers designed to function like skin and soft tissue (Mold Star 20T, Dragon skin FX-pro and Slacker). Casts were used to create the penile shaft model and the dorsal hooded foreskin model. The urethral plate was cast separately on a flat surface. The model was then assembled by hand. The model used for simulation included the penile shaft and urethral plate, while the dorsal-hooded foreskin was prepared to simulate the penile anatomy separately.

Trainees were then divided into two groups. Group 1 practiced the low-fidelity curriculum (3 tasks) and then performed dissection of the urethral plate and suturing using the intermediate-fidelity hypospadias model. Group 2 practiced hypospadias repair prior to the low-fidelity curriculum. Both groups’ models were scored by 3 blinded urologists. Trainees were then asked to complete a post simulation satisfaction survey. Data analysis was performed in IBM SPSS Statistics for Macintosh (Version 28.0 Armonk, NY: IBM Corp).

Results

Twenty-two candidates across Wisconsin, USA, and Dublin, Ireland participated in the study. This included 7 s-year residents, 9 third-year residents, 2 fourth-year residents, and 3 fifth-year residents. Both Groups 1 and 2 had a similar distribution of trainees (p = 0.60). Group 1 outperformed group 2 in all tasks (p < 0.05, Table 1). Trainees reported that the platform was very useful (91%).

Discussion

Our curriculum showed improvement in trainee ability and comfort to perform hypospadias repair. Advantages of such a simulated curriculum include improving current resident training in microsurgery, improving surgical ergonomics for trainees prior to real-time experience, and decreasing the learning curve for trainees pursuing pediatric urology.

Conclusion

An intermediate-fidelity hypospadias platform externally validates the conceptual model implemented in the low-fidelity loupes curriculum. This appears to lead to improvement in loupe surgical skills regardless of trainee level.

Introduction

Hypospadias repair is an index pediatric urology procedure and as such, skill acquisition using surgical loupes is an integral component of training. For the purpose of acquiring loupes surgery skills, we recently developed a physical midshaft hypospadias model that is amenable for urethral plate dissection and suturing to augment this program.

Previously, an innovative curriculum to introduce basic concepts of microsurgical technique using loupe magnification was developed [1]. The Toronto practice curriculum is a 6-task low fidelity tool that deconstructs all the individual skill components required when performing surgical procedures using loupes. This was the first such curriculum to broach the concepts of microsurgery in a step-wise curriculum designed for trainees. These skills included: angled face suturing with a Castroviejo needle driver and forceps, parallel face suturing, scissor cuts with a Lawton scissors, scissor cuts with removal of tissue, picking up of a rice grain, and passing a rice grain back and forth only with finger and forceps. The authors used a 5-point scoring system (with 1 demonstrating difficulty and 5 demonstrating excellence) to systematically report trainees results on each exercise. Furthermore, they proposed a possible rat model for a simulation of hypospadias surgery as a bridge to live surgical exposure. To date, no advanced fidelity curriculum has been attempted. In addition, we developed a viable synthetic model that eliminated unnecessary risk to animals, such as rats, from an ethical standpoint [2]. Therefore, our objective was to assess the validity of the prior, low-fidelity conceptual model from this original curriculum using the metric of improved performance on our intermediate-fidelity silicone hypospadias model.

Materials and methods

Model development

Three-dimensional model development was prototyped in Solidworks^™ and designes were iteratively revised using feedback from an experienced pediatric urologist and medical physicist to achieve the agreed-upon penile size and shape of the ventral penile defect (Fig. 1A). The final model was designed to emulate features of midshaft hypospadias, whereas compared to the original sub-coronal version of the hypospadias model, this provided more surface area for practicing loupes surgical skills. For urethral dimensions, the model used for this study was created to accept an 8 French pediatric catheter. After all parameters had been confirmed, the design was 3D printed using a stereolithography (SLA) 3D printer (3D systems Viper Si2), creating a rigid polycarbonate-like version of the hypospadias model (Fig. 1B).

Fig. 1.

Model Simulation/Development in (A) Solidworks^™, (B) 3D printed and (C) After Silicone Casting and Urethral Plate attachment.

Model creation

To achieve the desired mechanical properties of the final model, the 3D printed version was used in a mold and casting process, utilizing pourable silicone rubber products (Smooth-On^™). Standardized measurements of each casted model were confirmed using a gram scale. Skin-like silicone pigments were used to differentiate components of the model for improved fidelity.

Creation of the penis mold was undertaken using a cut paper-towel roll for containment of poured materials and use of mold release spray for easy removal of the 3D-printed model. The silicone rubber (Mold Star^™ 20T) was used to pour 20 g of silicone over the model until submerged. This mold was then cured for 30 min and the print removed. The dorsal-hooded foreskin mold was made separately using the same series of steps, including computer-aided design, 3D printing, and model molding.

Next, the hypospadias models were cast from the molds. First, mold release was sprayed inside of the mold. Then, silicone rubbers were mixed (Dragon Skin^™ FX-Pro^™ parts A and B, and Slacker^™) in a 1:1:1 ratio, along with skin-color pigments. The mixture was poured into the previously developed mold, followed by a cure time of 40 min and model removal. Finally, the urethral plate was made using a lighter flesh-colored pigment and the same mixture ratio of silicone rubber products. Each plate was cast on a flat surface and created to be 1 mm in thickness. A scalpel was then used to craft the shape of the urethral plate by hand.

Model assembly

After the components of the penile shaft and urethral plate were cast, the models were assembled in the following sequence:

1. A nail was used to pierce the model along the axis of the urethra, creating a prescribed path for catheter insertion into the penis.

2. The urethral plate was attached to the penile cast with an adhesive (Skin Tite^™) mixed in a small plastic dish and held in place for 6–8 min. This assembled version was used for catheter insertion, urethral plate dissection, and urethral plate suturing (Fig. 1C).

Study participant selection

Urologic surgery residents were included in the study population. The residents received a theoretical lecture covering the basic knowledge of loupes surgery, stressing the aspects of tissue handling, instrument handling and knot tying. To replicate real time surgical skills, we selected 3 of the 6 low fidelity skills - (1) Parallel Face Suturing (urethroplasty), (2) Scissor Cut (urethral plate dissection and degloving), and (3) Rice Transfer to Hole (tissue handling). To that end, the residents used the hypospadias model for urethral plate dissection and suturing.

Training approach

Following this, the residents were randomly divided into two groups. Group 1 practiced on the low fidelity curriculum (3 tasks) and then performed dissection of the urethral plate and suturing using the intermediate fidelity hypospadias model, while group 2 performed the hypospadias procedural task first, followed by the low fidelity exercises.

Each resident had 55 min to practice (25 min for the low fidelity curriculum and 30 min for hypospadias model). The final products for both the low (suturing and scissor cut) and intermediate fidelity models were then blindly reviewed by three independent attending pediatric urologists and graded on accuracy and the result using a Likert scale of 1–5 (Fig. 2). This rubric was developed specifically for this study. Trainees were then asked to complete a survey to assess their overall satisfaction with and impressions of the course.

Fig. 2.

Scoring rubric.

Statistical analysis

Data analysis was performed in IBM SPSS Statistics for Macintosh (Version 28.0. Armonk, NY: IBM Corp). We assessed descriptive statistics to compare Groups 1 and 2. Next, we used Mann-Whitney-U tests to analyze group differences for non-normally distributed data, and Pearson’s correlations to ascertain associations between continuous variables. Inter-rater reliability of our scoring rubric was calculated using a Cohen’s κ. A p-value of <0.05 was designated as statistically significant.

Results

Demographics

Twenty-two candidates across Wisconsin, USA and Dublin, Ireland, completed the blinded study to the evaluators. In total, 7 s-year residents, 9 third-year residents, 2 fourth-year residents, and 3 fifth-year residents participated in the study. Training levels overall were not significantly different between Group 1 and Group 2 (median post-graduate year 3, p = 0.6).

Performance scores

Those candidates who undertook the pre-hypospadias model skills tasks outperformed those who completed the hypospadias repair first by both time and level of overall task completion (Table 1). Cutting (r = 0.49, p = 0.03), was significantly associated with the hypospadias repair score, while the suturing score did not correlate with the hypospadias score (r = 0.26, p = 0.3). Examples of scored hypospadias repairs are visible in Fig. 3.

Table 1.

Performance scores.

Task	Group 1 Median (range)	Group 2 Median (range)	P-value
Suturing	3.5 (1)	2.0 (1)	0.01
Cutting	4.5 (1.25)	3 (2)	0.04
Hypospadias Repair	5 (1)	3.5 (1)	0.04

Fig. 3.

Example of Scored Hypospadias Repairs given a score of (A) 1 and (B) 5.

Reliability of scoring rubric

Three reviewers performed a blinded review of the suture, cutting, and hypospadias models. Overall, inter-rater reliability (Cohen’s κ) of our rubrics for suturing, cutting, and hypospadias repair were assessed between the three reviewers at each site. The, inter-rater reliability of our rubric for suturing was good (κ = 0.79, 0.88), while the inter-rater reliability for cutting (κ = 0.89, 0.93) and hypospadias (κ = 0.95, 0.92) were excellent.

Satisfaction rates

Trainee satisfaction rates were very high, with 73% of respondents after the platform stating that they would be happy to attempt a hypospadias repair under supervision. Ninety-one percent of respondents found this model to be a very useful platform, and 82% believing that the steps of the operation were adequately duplicated.

Discussion

For several reasons, surgical simulation is now becoming a more widely recognized mechanism to improve the quality of surgical training. First, simulation reproduces a real-world scenario in a controlled less intense setting and has therefore become a prominent complement within medical education. Second, simulations can be performed outside of working hours on the trainee’s own time. Third, this flexibility allows certain procedural skills to be customized or repeated for a trainee’s needs, without compromising patient safety and offering improved outcomes through skill-based repetition. Finally, a curriculum using silicone models, rather than animal models, avoids the problems with unethical or unnecessary harm to animals while providing the needed benefit to surgical training [2].

In this study, we reported significant improvement in trainee skills and overall high trainee satisfaction (73%) with an intermediate fidelity silicone training model for the practice of hypospadias repair using loupe magnification. This study builds on the findings of prior authors [1], who demonstrated that a low fidelity curriculum could improve microsurgical skills. The findings of our pilot study are encouraging and build on those of the Toronto practice curriculum, in which 6 specific exercises were identified as low-fidelity measures to practice excellent psychomotor coordination and technique. We selected three of these 6 key skills and were able to demonstrate a statistically significant improvement in skill acquisition and completion of a hypospadias repair after practicing of these three skills.

There are several advantages to creating a formal microsurgical curriculum. First, although microsurgical training is not yet a formal requirement from the ACGME for urology trainees [3], many surgeons agree that this should be added to current ACGME requirements. Currently, 80% of programs have at least one trained microsurgery expert in andrology or pediatric urology. To ensure that trainees are able to maximize their experience on these rotations, a formal, graduated microsurgical curriculum would be of benefit. Our results demonstrate that trainees feel comfortable replicating a hypospadias repair under supervision up to 73% of the time using our intermediate fidelity model. In addition, our scoring rubric provides guidance on how evaluators can consistently review trainees’ hypospadias repairs. As discussed above, our rubric had good or excellent interrater reliability in all three categories. In future studies, will consider comparing this rubric to that proposed by the Objective Structured Assessment of Technical Skills [4], and will solicit input from pediatric urologists from multiple centers to ascertain agreement on the items included in the scoring rubric.

Newer studies cite concerns about learning improved surgical ergonomics, which may be learned in a simulated environment, prior to working in the operating room [5]. As demonstrated in our simulated environment, 82% of participants reported that they could replicate the work in the simulation in the operating room, suggesting that simulation is an appropriate time to introduce optimal ergonomic technique. Although this was not assessed in our study, ergonomics in loupe surgery are of particular concern. Traditional loupes are intended to help improve vision and often force users to excessively tilt their heads, resulting in chronic neck pain and injuries [6]. Recently, ergonomically fitted loupes support a neutral neck posture where the head tilt is less than 25°. Considering ergonomics when selecting loupes and learning how to optimally position patients during surgery is important to consider in a simulated setting.

We have not yet formally compared our model head-to-head with those proposed by other investigators. One group proposed a low-fidelity model using gloves to create a hypospadias repair simulation [7]. Benefits of this model included low cost feasible tubularization of the urethra for urethroplasty. However, the authors noted that the transurethral plate incision would destabilize the model and preclude completion of the repair. In addition, the authors noted limitations in foreskin reconstruction in 3 parts. Unlike this model, our model facilitated all steps of urethral dissection and urethroplasty. However, our model did not include attached foreskin to simulate foreskin reconstruction. This issue will need to be addressed in future model iterations. An industry-sponsored acrylic model [8] which includes 8 different types of hypospadias allows for greater complexity of repair with all components. However, this model has not yet been validated. We would also need to compare the cost of mass-producing our silicone simulation to that of the acrylic simulation to make a cost comparison. We will consider doing head-to-head comparisons of our simulation with the glove and acrylic simulations in future studies.

Finally, there is robust literature available on the learning curve for hypospadias surgery [9–11]. Our authors have also previously published on the time to “learn,” develop “competence” and develop “proficiency.” [11] A microsurgical model on which to improve the “learning” phase of hypospadias surgery could expedite the learning curve and facilitate sooner acquisition of both competence and proficiency. For this reason, we believe this training curriculum could have wider application and implementation for pediatric urology fellows as well.

Our study does have limitations. First, our pilot sample size is too small to ascertain reproducibility of improvements in surgical technique and overall user satisfaction with the silicone model. This will be addressed in future, larger scale, multi-center collaborations, in which we do anticipate iterative revisions of our silicone model based on user feedback. Second, the cost to build the model will need to be considered for larger training groups. We hope to assist other centers with building similar models to demonstrate feasibility and reproducibility of our training curriculum. Further, we did not use the model to improve posture, which is an important consideration, as detailed above. Additionally, this was only a feasibility study. Additional studies will be needed to educationally validate our simulation by comparing experienced to novice surgeons.

Finally, we did not study the utility of this curriculum in fellows, who may benefit from such a curriculum at the beginning of their dedicated pediatric urology training. Future studies will extend this model to trainees of all levels to see if this curriculum enhances or expedites skill acquisition.

Conclusion

Overall, our intermediate-fidelity hypospadias platform externally validates the conceptual learning model implemented in the Toronto curriculum. This pilot curriculum appears to improve surgical skills regardless of trainee level. We believe these findings are encouraging for future efficacy and reproducibility of our curriculum in larger-scale studies. Future iterations of this training curriculum will build on this intermediate fidelity model using an ergonomically-optimized, high-fidelity model using motion with pressure sensors to improve skill acquisition.