Effective intracorporeal space in robot-assisted multiquadrant surgery in a pediatric inanimate model


Pediatric robot-assisted surgery is technically challenging, but it is becoming the most desirable approach for most of the pediatric urological abdominal surgical procedures. Distance between ports has been adopted based on adult surgery experience. Currently, there is scarce information and literature about effective trocar position and distance between ports for highly complex pediatric multiquadrant surgery. The aim of this study is to evaluate the most effective way of port placement for pediatric multiquadrant robot-assisted surgery using an inanimate model. Two inanimate models simulating the abdominal area of an older infant were created: model (1) 33.3 × 29.6 × 11.5 cm and model (2) 15 × 13 × 8 cm. A simulation of a robot-assisted laparoscopic Mitrofanoff procedure was performed in both models simulating appendix procurement and subsequent anastomosis to the bladder dome. In the first model, the simulation was performed in two ways: (a) adult trocars were placed with a distance of 4 cm between them and placed longitudinally and (b) ports were placed by triangulating the camera 2 cm in a cephalic fashion. In the second model, (a) scenario was used as described above (c) single port crossing the arms. Volume of the first model was 11,335.32 cm3. Simulation (b) reached higher percentage of volumes without arm clash (30.19 vs. 41.92%, p = 0.021). In the second model with a volume of 1560 cm3, simulation (a) reached a volume percentage of 65.15% without arm clash and allowing the multiquadrant advance, while simulation (c) could not be performed due to arm collision and the inability to advance and see the four quadrants. Triangulation and increasing the distance away from the point of interest improve intracorporeal EWS for multiquadrant complex pediatric surgery.


The latest advances in equipment and surgical techniques, propose minimally invasive surgery as a new standard of management in adults and children [1]. When compared to open surgery, laparoscopy is associated with minimal comorbidity and shorter recovery times [2]. The introduction of the da Vinci surgical system, has expanded the possibilities of considering the performance of more technically challenging cases [3]. Thus, more complex procedures can be performed with shorter learning curves [4, 5].

In urology, robot-assisted laparoscopic radical prostatectomy has had an exponential growth and introducing the possibility of performing new procedures such as partial nephrectomies, pyeloplasties, and radical cystectomies [6, 7]. The most frequently performed procedure in pediatric urology is pyeloplasty, which has enabled the opportunity of introducing the use of robotic surgery in the pediatric field [5, 7, 8].

The pediatric patient represents more challenging variables due to a smaller working space where adult instruments must be used. Most pediatric surgeons have incorporated technical recommendations for port placement from adult experience without current basic science literature on this topic [2, 9]. The positioning of the trocars helps to minimize arm collisions and reduces operative time [10].

These collisions are minimized significantly when the distance between the iliac spines is higher than 13 cm or if the puboxyphoid distance is higher than 15 cm [11]. Also, trocars should be placed 3–5 cm apart from each other; however, in very young children, this is not always achievable and the greatest possible distance should be used. The "burping" maneuver allows a 1–2 cm and increases the intracorporeal working space [12].

The aim of this study was to evaluate the most effective way of port placement for pediatric multiquadrant robot-assisted surgery simulated with an inanimate model.

Materials and methods

The protocol of this study was accepted as a non-risk experiment by the Institutional Ethics Committee. Two inanimate models were built to simulate the abdominal area. Model number one (Fig. 1a) had a total volume (V) of 11,335 cm3. Model number two (Fig. 1b) had a total V of 1560 cm3. These volumes were chosen based on previous publications about ideal abdominal wall surface and average pediatric patient’s anthropometric measurements [11, 13].

Figure 1

a Child’s inanimate model, b toddler’s inanimate mode

Inside every model, the four abdominal quadrants were marked, and balloons were placed as kidneys, bowel, bladder, and urethra.

The da Vinci® Si Surgical System (Intuitive Surgical, USA, 2009) with a 30° downward lens was used. In the first model, two sets of measurements were performed by two different surgeons doing the procedure. Simulation (a) consisted of the placement of the camera 8.5 mm trocar at the level where the belly button is supposed to be. Two more ports were placed on a completely horizontal line at 4 cm apart from each other, one at the right and one at the left (Fig. 2a). The remote center was left above the abdominal wall. For simulation (b), the same port distances were used as for simulation (a), but the camera trocar was triangulated and placed 2 cm more cephalad than the other trocars (Fig. 2b, c). All trocars were placed at remote center and camera port 2-cm deep (Fig. 3).

Figure 2

ac Port placement distance and triangulation

Figure 3

Toddler’s model. a Simulation (b). b Simulation (c)

For all port placement simulation scenarios, a complete visualization of the four quadrants was attempted. Then two surgeons performed a simulated Mitrofanoff procedure separately. We chose the Mitrofanoff procedure arbitrarily, considering it a complex reconstructive case where multiquadrant surgery may be required. But this model could be extended to bladder augmentation procedures, MACE etc. [14]. The appendix was procured in the upper quadrant and subsequently moved caudally to another quadrant for bladder anastomosis.

The distance reached at every quadrant was marked and measured for each simulated scenario, and the collision of arms was also evaluated. This way, using the Pythagoras theorem (Fig. 4), the distances and areas of coverage were calculated. Every simulation was measured twice (for each surgeon).

Figure 4

Application of Pythagoras theorem to inanimate models and reached distances

The V of the models was calculated according to the equation V = L × W × H. The reached volumes were calculated according to the measured distances within the models.

Picture acquisition and data collection were performed in real time while scenarios were being conducted. Data analysis was performed with SPPS 25.0 (IBM, USA, 2018). Central tendency measures were evaluated for reached V and percentage of reached V. Also, tests for normality were run. Differences between distributions were used to compare the variables reached among the simulations for each model, with Kruskal–Wallis test for non-parametric variables and ANOVA test for independent samples for parametric distributions. To compare before and after burping, t test for related samples were used in parametric variables and Wilcoxon test in non-parametric. A p < 0.05 was considered significant.


The average reached V was 2147.33 cm3 \(\pm\) 1858.63 and the average percentage of reached V was 33.05% \(\pm\) 22.81. When compared before and after burping, there was no difference for reached V (1983.81 cm3 \(\pm\) 1825.65 vs. 2310.86 cm3 \(\pm\) 2157.84, p = 0.145) or percentage of reached V (30.93% \(\pm\) 23.29 vs. 35.15% \(\pm\) 25.7, p = 0.053).

When compared by simulation in non-burping measures, percentage of reached V was higher in model 1, simulation b (35.71%) and in model 2, simulation a (59.23%), p = 0.021. After burping, the percentage of V reached was 41.92 in 1b and 65.15 in 2a (Table 1).

Table 1 Summary of results

The advance of arms was successful in both simulations on model one but only in simulation a on model 2, allowing the performance of the simulated Mitrofanoff procedure with right visibility of four abdominal quadrants, and the adequate movement of the instruments. When arms collided, the procedure was stopped, and maximum distances were measured. The unsuccessful advance in 2c was caused by the collision of the arms where we could not appropriately see all the quadrants and reach the simulated organs. Arm collision and the inefficacy of instrument movement limited the procedure and it could not even be started.


The introduction of pediatric urology robot-assisted surgery has been documented in case reports and case series, based on the experience of robot-assisted surgery in adults and more recently in children [2]. To date, the major point of discussion is around the current limitations of doing robot-assisted surgery in pediatrics using the adult experience and recommendations. Our results support the importance of triangulation and displacing ports at different anatomical locations than what has been described in the adult field allowing the performance of highly complex multiquadrant surgery.

Finkelstein et al. evaluated 45 children between 3 and 12 months old who underwent pediatric urology robot-assisted surgery and stated 13 cm as an optimal distance between the iliac spines and 15 cm as the puboxyphoid distance to diminish the number of arm collisions during the procedure [11]. Thus, our inanimate models were built simulating the abdominal volume of a child and a toddler. Also, Kim et al. recommended to place the trocars every 3–5 cm; however, these distances might not be possible to be reached in small kids [12]. Our results support that the most efficient distance between ports is 4 cm apart.

The triangulation of the camera at least 2 cm away from the point of interest allows arms to reach better volumes of intracorporeal effective working space (EWS). The benefit of a very elastic abdominal wall in children has the benefit of enabling the use of the “burping” maneuver as a great benefit with an increase of 6% in the EWS. Nonetheless, it is important to consider that this tension on the abdominal wall may have an impact on postoperative pain. Another adaptation that pediatric surgeons use is the displacement of the remote center away of the abdominal wall which may also have an effect on abdominal wall tension and postoperative pain. Future studies will be needed on this topic as it is our perception that patients have better postoperative pain control when remote center can be placed at the abdominal wall.

With the upcoming platforms, single-port surgery is a promising alternative of pediatric patients. Nonetheless, our results showed more arm collision and only allowed the advancement of the arms vertically. Similar results to the experience found by Thakre et al., with their experience in small working spaces [15]. Our single-port model showed a 3% coverage of intracorporeal EWS when compared to the standard three independent port placement models. With this simulation, not only collision was a limitation but the size incision was too considering that for open surgery, this may be a similar size. Based on our results, we do not recommend the use of single-port robot-assisted surgery in infants with similar anthropometric measurements as our models.

It is important to highlight that one of our interests with this project was to develop an inanimate model to reduce the need for animals for these kind of studies for ethical reasons. A recent bibliometric analysis on minimally invasive surgery in children showed virtually no studies published using animal or inanimate models [2]. Current technologies in 3-D printing may open the doors to further expand the knowledge and evolve pediatric minimally invasive surgery. Areas of interest for future studies will need to focus on reducing instrument and port size, including depth of the remote center, postoperative pain.


Port placement triangulation and placing it away from point of interest increases the EWS and allowing multiquadrant surgery. With the current platforms available, single-port surgery for children may not be recommended for highly complex pediatric intra-abdominal surgery.


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Intuitive provided training surgical instruments for the present study.

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Correspondence to Nicolas Fernandez.

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For the present manuscript, all authors whose names appear on the submission have made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work. All have drafted the work or revised it critically for important intellectual content. Before submission, all authors approved the version to be published; and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Authors: Nicolas Fernandez, Catalina Barco-Castillo, Ali ElGhazzaoui and Walid, Farhat declare no conflicts of interest.

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Fernandez, N., Barco-Castillo, C., ElGhazzaoui, A. et al. Effective intracorporeal space in robot-assisted multiquadrant surgery in a pediatric inanimate model. J Robotic Surg 15, 25–30 (2021). https://doi.org/10.1007/s11701-020-01065-8

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  • Robotics
  • Reconstructive surgical procedures
  • Pediatrics
  • Surgery
  • Minimally invasive