The Optigrip® is a reusable laparoscopic grasper as usual with a pistol grip. The shaft is inserted into the handpiece with the pistol grip and is interchangeable. The specific tissue resistance which is felt by the grasping beak creates a tension on a fiber Bragg (5) sensor on a glass fiber in the beak (Fig. 1). This tension creates a shift of the reflected light frequencies by the fiber Bragg gratings on the level of nanometers caused by the compressing or stretching of these gratings (6, 7). This light frequency change of the light reflection is measured 6000 pro second in the control box Optigator which translates this in an activation of the actuator in the handgrip. The specific tissue resistance is felt as resistance on the gripper once the surgeon closes the beak. Not only the resistance of the tissue is felt grasping the tissue by closing the beak but also the tissue resistance against the beak from outside. This is important during preparing tissue and dividing tissue layers.

To optimize the feeling of minimal tissue differences on the fingertips a pistol grip was developed as a pistol grip is the most ergonomic gripper which also is preferred by the most surgeons (8). This study will compare the Optigrip® and a conventional laparoscopic grasper in feeling of arterial pulsations.

The pulse which can be sensed by touch during laparotomy is defined by the pressure difference between the diastolic and systolic pressure (Fig. 2). This pressure difference is more evident in arterial vessels and not in the veins REF. This pressure difference varies during the day, depending on our activity, the size of the artery and the specific wall thickness of the arteries (Figs. 2, and 3) [20]. The diameters of the critical arteries in minimal invasive surgery are small, with outer diameter varying between 1 and 8 mm (Fig. 3). The wall thickness of the arteries varies from 1 to 1.5 mm. (Fig. 3) [20, 21].

Pulse difference related to vessel type [20]

Diameter and wall thickness of vessels [21]

To define which arteries are of clinical importance in laparoscopic surgery, arteries were selected that are of clinical importance during surgery for the following medical specialties: urology, gynecology, and intestinal surgery. These arteries have been described (Table 1) and depending on their outer diameter and thickness of the wall divided into 4 groups (Table 2). To mimic these arteries, four silicone tubes have been made representing these four different groups of diameters. These tubes represent the average outer diameter, the wall thickness, and the inner diameter of these four categories.

A pressure pump created a systolic pressure of 120 mmHg. To control whether the pressure and so the pulse is stable and equal all over the length of these tubes, the relation between the applied force and pressure was tested. There appeared to be a linear relation between the force and the pressure for all the four tube sizes. (Fig. 4).

Linear relation between force and pulsation in all four artificial blood vessels

A laparoscopic box trainer was created in which the four artificial blood vessels were fixed. Also, a control tube without pulse was added (Fig. 5a and b).

a Pump and four prepared tubes. b Black box trainer with the 5 tubes inside

This study was conducted in the simulation lab of the Amsterdam Skills Centre (ASC, Amsterdam, The Netherlands). A randomized controlled trial study design was incorporated. Surgical residents (PGY 3–4) from Dutch teaching hospitals were included. IRB approval was acquired from the Amsterdam UMC and all participants provided written informed consent. A laparoscopic pulse sense test was performed using a black laparoscopic box trainer. Participants had to grasp the 5 tubes in a randomized sequence and they were asked whether they could feel the pulse. An assistant guided the grasper to the artificial vessels and the participant was allowed to grasp the tube for 3 s. The pulse sense test was performed using the haptic feedback grasper and a conventional laparoscopic grasper (KELLY grasping forceps, Karl Storz SE & Co. KG, Tuttlingen, Germany). A conventional laparoscopic curved dissection forceps was chosen due to its common usage in laparoscopic procedures for tissue manipulation and dissection, ensuring a realistic control.

The sequence of the use of these two graspers was done in a randomized order. The participants were blinded to the size of the tubes. After this grasping action they were asked whether they could feel the pulse yes or no. Once they grasped all five tubes with one grasper they repeated the procedure with the other grasper.

The results were scored as the number and percentage of correct answers. The percentages were calculated by adding all correct answers for every tool and comparing this to the maximum possible score for every tool (5 answers * 12 = 60.) It was expected that both graspers would at least have 20% of the answers correct as there was one non-pulsating control tube out of the total of five tubes. Based on a prior pilot study a post hoc power analysis was performed to determine the group size. Based on a power of 0.80 and a significance of 0.05 the sample size consisted of n = 11. These results were analyzed with the Wilcoxon signed rank test. Individual tube diameter and grasper were also compared using the Fisher’s Exact Test. Values of p < 0.05 were considered statistically significant.