Sequence and task analysis of instrument use in common laparoscopic procedures.

BACKGROUND: In the area of instrument evaluation, one aspect that still requires objective assessment is the dynamics of instrument maneuver and exchange. If we could gain a better understanding of these phenomena, we could improve the design of the instruments themselves. METHODS: A total of 29 laparoscopic procedures were videotaped and reviewed using time motion analysis. Instrument multifunctionality was determined using a standardized list of laparoscopic maneuvers. State transition diagrams were utilized to document the sequence of instrument exchanges. RESULTS: The curved dissector, atraumatic grasper, and cautery scissors were identified as the most multifunctional instruments; each was able to perform five distinct maneuvers. Instrument sequences were found to consist of a three-part dissect --> clip --> cut cycle and a two-part dissect --> suction cycle of instrument exchange. CONCLUSION: This study demonstrated that laparoscopic instruments are often used to perform a variety of maneuvers in addition to their primary function. Furthermore, there are common patterns in instrument exchange that provide a potential source of design parameters for improved surgical efficiency.

Design of multifunctional compliant mechanisms for minimally invasive surgery.

Compliant mechanisms that can perform multiple unique functions have great potential for use in minimally invasive therapy. A fully compliant mechanism may be thought of as a monolithic mechanism without hinge joints which uses elastic deformation to achieve force and motion transmission. Incorporating multifunctional compliant mechanisms into minimally invasive surgical tools has many possible advantages, including reduced instrument exchanges and additional dexterity at the surgical site. Compliant mechanisms also offer the advantage of single-piece construction and ease of manufacture over their rigid-link counterparts, eliminating the need for complex millimeter-scale assembly and cleaning in hinge areas. A multicriteria topology optimization procedure for the design of multifunctional compliant mechanisms is illustrated through the design of a combination tool that will perform forceps and scissor function. A working solid model of the combination forceps/scissors has been generated based on the optimal topology. Results of detailed finite element modeling are discussed along with implications for practical manufacture and implementation.