Objective Evaluation of Laparoscopic Surgical Skills Using Hidden Markov Models Based on Haptic Information and Tool/tissue Interactions

Laparoscopic surgical skills evaluation of surgery residents is usually a subjective process, carried out in the operating room by senior surgeons. By its nature, this process is performed using fuzzy criteria. The objective of the current study was to develop and assess an objective laparoscopic surgical skill scale using Hidden Markov Models (HMM) based on haptic information, tool/tissue interactions and visual task decomposition. Methods: Eight subjects (six residents: first year surgical residents 2xR1, third year surgical residents 2xR3 fifth year surgical residents 2xR5; and two expert laparoscopic surgeons: 2xES) performed laparoscopic cholecystectomy following a specific 7 step protocol on a pig. An instrumented laparoscopic grasper equipped with a three-axis force/torque sensor was used to measure the forces and torques at the hand/tool interface synchronized with a video of the tool operative maneuvers. A synthesis of frame-by-frame video analysis was used to define 14 different types of tool/tissue interactions each one associated with unique force/torque (F/T) signatures. HMMs were developed for each subject representing the surgical skills in terms of haptic information and tool tissue interactions. The statistical distance between the HMMs representing residents at different levels of their training and the HMMs of expert surgeons were calculated in order to evaluate the learning curve of selected steps of laparoscopic cholecystectomy. Results: The objective laparoscopic surgical skill learning-curve showed significant differences between all skill levels. The major differences between skill levels were: (i) magnitudes of F/T applied (ii) types of tool/tissue interactions used and with the transition between them and (iii) time intervals spent in each tool/tissue interaction and the overall completion time. The HMM analysis showed that the greatest difference in performance was between R1 and R3 and then decreased as the level of expertise increased. This objective evidence for a learning curve indicates that the surgical residents appear to acquire a major portion of their laparoscopic surgical capabilities between the first and the third years of their residency training. Objective Evaluation of Laparoscopic Surgical Skill J. Rosen, M. Solazzo, B. Hannaford, M. Sinanan American College of Surgeons Annual Meeting Washington State Chapter, Lake Chelan, June 2000 2