Perceiving haptic feedback in virtual reality simulators.

BACKGROUND: To improve patient safety, training of psychomotor laparoscopic skills is often done on virtual reality (VR) simulators outside the operating room. Haptic sensations have been found to influence psychomotor performance in laparoscopy. The emulation of haptic feedback is thus an important aspect of VR simulation. Some VR simulators try to simulate these sensations with handles equipped with haptic feedback. We conducted a survey on how laparoscopic surgeons perceive handles with and without haptic feedback. METHODS: Surgeons with different levels of experience in laparoscopy were asked to test two handles: Xitact IHP with haptic feedback and Xitact ITP without haptic feedback (Mentice AB, Gothenburg, Sweden), connected to the LapSim (Surgical Science AB, Sweden) VR simulator. They performed two tasks on the simulator before answering 12 questions regarding the two handles. The surgeons were not informed about the differences in the handles. RESULTS: A total of 85 % of the 20 surgeons who participated in the survey claimed that it is important that handles with haptic feedback feel realistic. Ninety percent of the surgeons preferred the handles without haptic feedback. The friction in the handles with haptic feedback was perceived to be as in reality (5 %) or too high (95 %). Regarding the handles without haptic feedback, the friction was perceived as in reality (45 %), too low (50 %), or too high (5 %). A total of 85 % of the surgeons thought that the handle with haptic feedback attempts to simulate the resistance offered by tissue to deformation. Ten percent thought that the handle succeeds in doing so. CONCLUSIONS: The surveyed surgeons believe that haptic feedback is an important feature on VR simulators; however, they preferred the handles without haptic feedback because they perceived the handles with haptic feedback to add additional friction, making them unrealistic and not mechanically transparent.

A study of psychomotor skills in minimally invasive surgery: what differentiates expert and nonexpert performance.

BACKGROUND: A high level of psychomotor skills is required to perform minimally invasive surgery (MIS) safely. To assure high quality of skills, it is important to be able to measure and assess these skills. For that, it is necessary to determine aspects that indicate the difference between performances at various levels of proficiency. Measurement and assessment of skills in MIS are best done in an automatic and objective way. The goal of this study was to investigate a set of nine motion-related metrics for their relevance to assess psychomotor skills in MIS during the performance of a labyrinth task. METHODS: Thirty-two surgeons and medical students were divided into three groups according to their level of experience in MIS; experts (>500 MIS procedures), intermediates (31-500 MIS), and novices (no experience in MIS). The participants performed the labyrinth task in the D-box Basic simulator (D-Box Medical, Lier, Norway). The task required bimanual maneuvering and threading a needle through a labyrinth of 10 holes. Nine motion-related metrics were used to assess the MIS skills of each participant. RESULTS: Experts (n = 7) and intermediates (n = 14) performed significantly better than the novices (n = 11) in terms of time and parameters measuring the amount of instrument movement. The experts had significantly better bimanual dexterity, which indicated that they made more simultaneous movements of the two instruments compared to the intermediates and novices. The experts also performed the task with a shorter instrument path length with the nondominant hand than the intermediates. CONCLUSIONS: The surgeon's performance in MIS can be distinguished from a novice by metrics such as time and path length. An experienced surgeon in MIS can be differentiated from a less experienced one by the higher ability to control the instrument in the nondominant hand and the higher degree of simultaneous (coordinated) movements of the two instruments.

Limitations of haptic feedback devices on construct validity of the LapSim® virtual reality simulator.

BACKGROUND: Surgeons performing laparoscopy need a high degree of psychomotor skills, which can be trained and assessed on virtual reality (VR) simulators. VR simulators simulate the surgical environment and assess psychomotor skills according to predefined parameters. This study aimed to validate a proficiency-based training setup that consisted of two tasks with predefined threshold values and handles with haptic feedback on the LapSim(®) VR simulator. The two tasks have been found to have construct validity in previous studies using handles without haptic feedback. METHODS: The participants were divided into three groups: novices (0-50 laparoscopic procedures), intermediates (51-300 laparoscopic procedures), and experts (more than 300 procedures). It was assumed that psychomotor skills increase with experience. All participants conducted the tasks lifting and grasping and fine dissection 20 times each. Validity of the training setup was investigated by comparing the number of times each participant passed a predefined threshold level for a set of 19 parameters. RESULTS: Construct validity was established for one parameter; "misses on right side" on the lifting and grasping task, whereas the other 18 parameters did not show construct validity. CONCLUSION: The setup employed in this study failed to establish construct validity for more than one parameter. This indicates that the simulation of haptic feedback influences the training performance on laparoscopic simulators and is an important part of validating a training setup. A haptic device should generate haptic sensations in a realistic manner, without introducing frictional forces that are not inherent to laparoscopy.

Intracorporeal suturing: economy of instrument movements using a box trainer model.

STUDY OBJECTIVE: To determine whether economy of instrument movement can differentiate between skills levels during intracorporeal suturing using a box trainer model. DESIGN: Prospective cohort study (Canadian Task Force classification II-2). SETTING: Skills laboratory of a university teaching hospital. SUBJECTS: Forty-two volunteers participated including 19 medical students without previous laparoscopic experience (novices), 12 residents in obstetrics and gynecology (intermediates), and 11 practitioners of intracorporeal suturing who had performed at least 200 laparoscopic procedures including advanced surgery (experts). INTERVENTIONS: Each participant performed 3 consecutive standardized intracorporeal sutures using a box trainer, and instrument movements were recorded using the TrEndo tracking device. MEASUREMENTS AND MAIN RESULTS: Time, path length, motion in depth, and motion smoothness of the instrument tips were recorded. Performance in the 3 groups differed significantly (p <.001 for all parameters; Kruskal-Wallis test). Experts outperformed novices in all 4 parameters (p <.01; Bonferroni test). CONCLUSION: The construct validity has been suggested for time, path length, motion in depth, and motion smoothness for assessment of the laparoscopic suturing task using a box trainer. An expert level has been set for training and assessment purposes. The addition of economy of movement to time to complete the task has the potential to refine acquisition of skills.