Objective Differentiation of Force-Based Laparoscopic Skills Using a Novel Haptic Simulator

Background

There is a growing need for effective surgical simulators to train the novice resident with a core skill set that can be later used in advanced operating room training. The most common simulator-based laparoscopic skills curriculum, the Fundamentals of Laparoscopic Skills (FLS), has been demonstrated to effectively teach basic surgical skills; however, a key deficiency in current surgical simulators is lack of validated training for force-based or haptic skills. In this study, a novel haptic simulator was examined for construct validity by determining its ability to differentiate between the force skills of surgeons and novices.

Methods

A total of 34 participants enrolled in the study and were divided into two groups: novices, with no previous surgical experience and surgeons, with some level of surgical experience (including upper level residents and attendings). All participants performed a force-based task using grasping, probing, or sweeping motions with laparoscopic tools on the simulator. In the first session, participants were given 3 trials to learn specific forces associated with locations on a graphic; after this, they were asked to reproduce forces at each of the locations in random order. A force-based metric (score) was used to record performance.

Results

On probing and grasping tasks, novices applied significantly greater overall forces than surgeons. When analyzed by force levels, novices applied greater forces on the probing task at lower and mid-range forces, for grasping at low-range forces ranges and, for sweeping at high-range forces.

Conclusions

The haptic simulator successfully differentiated between novice and surgeon force skill level at specific ranges for all 3 salient haptic tasks, establishing initial construct validity of the haptic simulator. Based on these results, force-based simulator metrics may be used to objectively measure haptic skill level and potentially train residents. Haptic simulator development should focus on the 3 salient haptic skills (grasping, probing, and sweeping) where precise force application is necessary for successful task outcomes.

Introduction

Proficiency in laparoscopic surgery requires mastery of a complex skill set that is fundamentally different from open surgery.¹ In particular, the forces experienced through laparoscopic instruments are fundamentally different from those experienced in open surgery wherein surgeons directly touch tissues with gloved hands. In laparoscopy, the forces from tissue interactions are combined with friction in the trocar as well as the pivoting of the tools causing a fulcrum effect.2, 3, 4, 5 As a result, learning to accurately interpret forces felt with tools, and apply controlled forces using them, is challenging for novice surgeons.

Several investigators have sought to analyze forces exerted by surgeons during laparoscopy.2, 6, 7 Richards and coworkers' detailed study, for example, documented force data from expert laparoscopic surgeons and novices as they performed 2 common laparoscopic procedures on an animal model.⁶ Analysis of in vivo force data revealed that expert surgeons and novices differed in the magnitude of forces applied with laparoscopic tools. Differences in applied forces were significant for 3 surgical skills: grasping, probing, and sweeping (shown in Fig. 1).⁶ Grasping was defined as applying pinch forces on tool handles to grasp and handle tissues. Probing was defined as using the laparoscopic tool to prod the tissue and perform dissection, a large part of laparoscopic procedures. Sweeping was defined as the lateral motion of the tool as tissues and organs are moved or cleared to reach the surgical site of interest. On all 3 skills, expert surgeons applied precise and controlled forces demonstrating superior haptic skills.6, 8, 9

Training the force-based surgical skills of novice surgeons and residents is especially important because a majority of surgical errors during laparoscopy are caused because of improper application of forces.¹⁰ However, no known validated training methods or curricula address this aspect of surgical skills training. Currently, residents learn haptic skills while practicing on animal models in the operating room while receiving verbal feedback from experts. Though operating room training cannot be completely eliminated or replaced, we believe that it can be optimized by initial training on simulators (Fig. 2).

Current laparoscopic skills training methods are depicted in Figure 2, including both simulators and operating room-based training. The current standard for basic laparoscopic skills training is the Fundamentals of Laparoscopic Surgery (FLS) curriculum and trainer which includes 5 basic hand-eye coordination and suturing tasks.¹¹ This simulator-based curriculum has been demonstrated to effectively develop basic laparoscopic skills that transfer to the operating room (predictive validity).12, 13, 14, 15 Simulator-based training can thus enable better-prepared surgeons entering the operating room. Further, there are other inherent advantages to using simulators that include objective assessment of skill and the ability to practice in a penalty-free environment.

The FLS curriculum, however, does not currently include training for force-based laparoscopic skills. Consequently, there is a need for developing haptic skills simulators that will shift the learning of initial force-based skills away from the operating room. This would enable residents entering the operating room to be better equipped with a wider skill set and be better prepared to benefit from operating room training.

What is remarkable about the success of the FLS skills training curriculum is that the program does not seek to realistically recreate the surgical environment; rather, the 5 training tasks recreate the salient or core hand-eye coordination skills that are basic to perform laparoscopic surgery. Similarly, it is hypothesized that there is also a set of salient haptic skills needed for skilled laparoscopy.

Based on previous studies,6, 16, 17, 18 we propose 3 salient haptic laparoscopic skills that require skilled application of forces: grasping, probing, and sweeping. A novel simulator for rendering these 3 force skills was developed and tested previously.¹⁹ As a first step toward validating the haptic simulator, this study specifically addresses its construct validity, i.e., can the simulator differentiate between expert and novice haptic skill? The overall hypothesis of this study is that surgeons will apply significantly different force magnitudes than those of novices in all 3 haptic skills. The outcomes of this study will directly contribute toward the development of haptic simulators for initial, simulator-based skills training.