Skills evaluation in minimally invasive surgery using force/torque signatures

Background: One of the more difficult tasks in surgical education is to tea ch the optimal application of instrument forces and torques necessary to fa cilitate the conduct of an operation. For laparoscopic surgery, this type o f training has traditionally taken place in the operating room, reducing op erating room efficiency and potentially affecting the safe conduct of the o peration. The objective of the current study was to measure and compare for ces and torques (F/T) applied at the tool/hand interface generated during l aparoscopic surgery by novice (NS) and experienced (ES) surgeons using an i nstrumented laparoscopic grasper and to use this data for evaluating the sk ill level. Methods: Ten surgeons (five-NS, five-ES) performed a cholecystectomy and Ni ssen fundoplication in a porcine model. An instrumented laparoscopic graspe r with interchangeable standard surgical tips equipped with a three-axis F/ T sensor located at the proximal end of the grasper tube was used to measur e the F/T at the hand/tool interface. In addition, one axis force sensor lo cated at the grasper's handle was used to measure the grasping force. F/T d ata synchronized with visual view of the tool operative maneuvers were coll ected simultaneously via a novel graphic user interface incorporated pictur e-in-picture video technology. Subsequent frame-by-frame video analysis of the operation allowed a definition of states associated with different tool /tissue interactions within each step of the operation. F/T measured within each state were further analyzed using vector quantization (VQ). The VQ an alysis defines characteristic sets of F/T in the database that were defined as F/T signature. Results: The magnitude of F/T applied by NS and ES were significantly diffe rent (p < 0.05) and varied based on the task being performed. Higher F/T ma gnitudes were applied by NS than by ES when performing tissue manipulation, whereas lower F/T magnitudes were applied by NS than by ES during tissue d issection. Furthermore, the time to complete the surgical procedure was lon ger for NS by a factor of 1.5-4.8 when compared to the time for ES. State a nalysis suggests that most of this time is consumed in an [idle] state, in which movements of the surgeon make no tissue contact. Conclusions: Preliminary data suggest that F/T magnitudes associated with t he tool/tissue interactions provide an objective means of distinguishing no vices from skilled surgeons. Clinical F/T analysis using the proposed techn ology and methodology may be helpful in training, developing surgical simul ators, and measuring technical proficiency during laparoscopic surgery.