The study was performed in the Department of Surgical Sciences at “Sapienza”—University of Rome, Rome, Italy. The study was approved by the local Ethics Committee (protocol 518/13) which is the Ethical Committee of the Umberto I Hospital, “Sapienza”-University of Rome. All subjects were enrolled into the study on a voluntary basis and each participant provided full written informed consent. All participants completed a questionnaire assessing demographics as well as number and type of previous laparoscopic procedures. We recruited 20 participants and divided them into two groups according to their experience in laparoscopic surgery. The first group, the inexperienced group, included 10 post-graduate first year residents (PGY 1) in general surgery (mean age 26.1 ± 1.9 years) with none or low laparoscopic experience (less than 5 laparoscopic procedures, all of them as camera operator). The second group, the LAP experienced group, included 10 surgeons (mean age 36.2 ± 3.6 years), performing more than 50 laparoscopic procedures as first operator.
All subjects had no prior experience with FLS and LESS surgery.
Participants performed the FLS pegboard transfer task and the FLS pattern cutting task on a laparoscopic box trainer, using at first conventional laparoscopy for familiarization, then the SPIDER surgical system. To avoid potential outcome inhomogeneity, every participant was blinded to other surgeons’ performances.
FLS tasks
Fundamentals of Laparoscopic Surgery (FLS) is a program of SAGES and the American College of Surgeons (SAGES/ACS, FLS Program, Los Angeles, CA, USA) designed to teach and evaluate the fundamental skills for laparoscopic surgery. The manual skills component is based on the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS) program which consists of five basic tasks performed on a laparoscopic box trainer: pegboard transfer, pattern cutting, endo-loop placement, intracorporeal and extracorporeal knot [10]. In order to evaluate the performance differences between SPIDER and conventional laparoscopy, we chose the pegboard transfer and the pattern cutting task. These tasks are not technically challenging and suitable even for beginners. The pegboard transfer task (Task 1) requires the operator to grasp six small pegs from a board, transfer them to the other hand, and place them on a second pegboard. The procedure is then reversed.
As the study included novice participants, the cutoff time was increased from 300 to 600 seconds.
According to MISTELS, the penalty score was defined as the percentage of pegs not transferred as a result of being dropped outside the field of view.
The pattern cutting task (Task 2) requires the participant to cut out a predrawn circle 5 cm in diameter from a 10 · 10 cm2 piece of gauze suspended between clips. One hand should be used to provide traction on the gauze using the grasper and to place the gauze at more favorable angles for the cutting hand.
As in the first task, the cutoff time was set at 600 seconds. According to MISTELS, the penalty was calculated as the percentage of the area of deviation from a perfect circle.
LAP simulator
The system used in the study was the Simulab LapTrainer (Simulab, Seattle, Washington). It consists of a 22″ h, 18″ w, 8″ d modular plastic box, a boom mounted, fully adjustable 1080p high definition camera with auto-focus, and a Universal Serial Bus (USB) 2.0 card connected to a 17″ laptop monitor. Standard-length laparoscopic instruments were inserted through two 12-mm working ports positioned approximately 18 cm apart in the pliable cover.
SPIDER simulator
The Simulab LapTrainer was modified to perform FLS tasks using the SPIDER surgical system.
A single 1.8 cm opening was made on the pliable cover of the box trainer, positioned between the previous port positions. The SPIDER surgical system was inserted through the single opening and was stabilized with an external support arm device.
To perform the FLS task we used a second-generation SPIDER surgical system with a vertebral design of the instrument delivery tubes.
Testing procedure and score calculation
Before performing tasks, all participants viewed a FLS instructional video illustrating the ideal way to perform each exercise.Testing sessions were conducted on two consecutive days. On the first day, both groups sequentially performed the pegboard transfer (Figure 1a) and the pattern cutting task (Figure 1c) using the LAP simulator. On the second day the same tasks were repeated using the SPIDER simulator (Figure 1b,1d).
Objective task score and subjective questionnaire rating scales were used to compare conventional laparoscopy and the SPIDER surgical system.
According to established methods of score calculation [8], each task was scored using the following formula in which higher scores reflect better performances:
$$ \mathrm{Task}\ \mathrm{score} = \mathrm{cutoff}\ \mathrm{time}\ \hbox{--}\ \mathrm{completion}\ \mathrm{time}\ \hbox{--}\ \mathrm{penalty}\ \mathrm{score} $$
Time and penalty measurements were performed by a proctor experienced in FLS evaluation.
A questionnaire was administered to all participants after each task to define conventional laparoscopy and SPIDER’s ease of use.
The subjective questionnaire rating was based on a six points Likert scale (1: very difficult, 2: difficult, 3: somewhat difficult, 4: somewhat easy, 5: easy, 6: very easy).
Statistical analysis
Continuous variables are presented as mean ± standard deviation. We assessed the normality of data with the Shapiro–Wilk test. Data of task score and subjective questionnaire ratings do not follow a normal distribution and therefore were reported as median and interquartile range. To evaluate the differences within groups we perform Wilcoxon test. To compare the performance of a specific group on LAP simulator versus SPIDER, we used the Mann–Whitney test and the Median test. A probability value of less than 0.05 was considered as statistically significant. All analyses were carried out with STATA v.12.