Quantifying surgeon grasping mechanics in laparoscopy using the Blue DRAGON system

Mechanical testing of abdominal organs has a profound impact on surgical simulation and surgical robotics development. Due to the nonlinear and viscoelastic nature of soft tissue it is crucial to test them in surgically relevant ranges of applied force, deformation, and duration for incorporating haptic realism into surgical simulators and for safe operation of surgical robots. In order to determine these ranges, a system known as the Blue DRAGON was used to track the motions and the forces applied to surgical tools during live procedures for quantifying how surgeons typically perform a minimally invasive surgical procedure. Thirty-one surgeons of varying skill were recorded performing three different surgical tasks. Grasping force (as applied to the tool handles) and handle angle for each tool were the signals of interest among 26 channels total acquired by the system in real time. These data were analyzed for their magnitudes and frequency content. Using the tool contact state, an algorithm selected tissue grasps to analyze measures during grasps only, as well as obtain grasp durations. The mean force applied to the tool handles during tissue grasps was 8.52 N +/- 2.77 N; maximum force was 68.17 N. Ninety-five percent of the handle angle frequency content was below 1.98 Hz +/- 0.98 Hz. Average grasp time was 2.29 s +/- 1.65 s, and 95% of all grasps were held for 8.86 s +/- 7.06 s or less. The average maximum grasp time during these tasks was 13.37 s +/- 11.42 s. These results form the basis for determining how abdominal tissues are to be mechanically tested in ranges and durations of force and deformation that are surgically realistic. Additionally, this information may serve as design specifications for new surgical robots or haptic simulators.