A Novel Sensorized Instrument-based Minimally Invasive Surgery (simis) Tool: Initial Construct Validation of Force Sensing

Objective: A novel sensorized laparoscopic instrument capable of sensing forces acting at the instrument tip in 5 degrees of freedom (DOF) as well as position in 6 DOF was evaluated. The purpose of this research was to demonstrate that the force sensing component is construct valid as evidenced by different force profiles between novice and expert laparoscopic surgeons.

Methods: Using an FLS trainer, eight Novice and 12 Expert laparoscopists performed the FLS suturing task using the novel instruments. The suturing task was broken down into three subtasks: Task 1, needle preparation; Task 2, needle driving; and Task 3, knot tying (3 throws per task). A novel MIS instrument with force sensors at its tip was used to compare their force profiles as indicated by force exertion over the total task and subtasks. Forces over the 5 DOFs were summarized as Total Force (magnitude of sum of forces in x, y, and z directions), Grasp Force, and Torsion. Normality was assessed using the d’Agostino-Pearson omnibus test. Gaussian force data were compared using the Student’s t-test and non-Gaussian data were compared using the Mann-Whitney test. Data are presented as means ± SD or medians ± interquartile range.

Results: In general, novices tended to be more erratic in their use of force in all 5 DOFs while experts generally tended to use little to no force for the bulk of the task until suddenly dramatically increasing their force exertion — especially in the x-direction and the grasp readings — when cinching down the three throws. There was a trend forExpertsto exert alower mean force over the course of the procedure thanNovices (0.73 N ± 0.30 vs. 0.91 N ± 0.32, p = 0.046). Experts exerted a significantly higher mean grasp force over the course of the procedure than Novices (21.84 N ± 6.87 vs. 15.14 N ± 7.17, p = 0.025). There were no differences between Novices and Experts for median torsion over the course of the procedure (0.03 N.cm, 0.02–0.08 vs. 0.03 N.cm, 0.02–0.05, p = 0.3080). Significant differences were demonstrated for Task 1 (1.00 N vs. 0.70 N, 0.48–0.88, p = 0.0294) with Novices exerting more total force than Experts. Similarly, for Task 3, knot tying, Novices demonstrated significantly greater total force than Experts (1.05 N, 0.59–1.22, vs. 0.65 N, 0.53–0.81, p = 0.0263). The results of subtask analysis for grasp force demonstrated non significant trends with Experts exerting greater force than Novices for Tasks 1 and 2. Considering all knots tied, expert surgeons used significantly more force than Novices (9.98 N, 5.58–19.83, vs. 22.62 N, 17.81–32.07, p < 0.0001). Subtask analysis for torsion did not show any significant differences.

Conclusions: The novel minimally invasive surgical instrument is construct-valid and capable of detecting differences in force exertion between novices and experts in the FLS suturing task. Further evaluation is mandated to better understand the ability to predict performance based on force as well as the potential for new metrics in minimally invasive surgical education.

Session: Podium Presentation

Program Number: S036

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