Feb. 20, 2002 University Park, Pa. --- Penn State engineers have developed new design software and are using it, in cooperation with surgeons from the University's College of Medicine, to develop new multi-task surgical tools that look like tiny jaws but will be able to bend around obstructions.
Dr. Mary Frecker, assistant professor of mechanical engineering and software team leader, says, "The new software doesn't replace a designer's intuition and experience but suggests a topology or layout based on the designer's specifications and the physical size constraints for the objective. Our software was specifically developed to aid in designing instruments that do more than one thing. Although some topology optimization software is used in industry, we're not aware of any, besides ours, for designing multi-task instruments."
Working with Dr. Randy S. Haluck, director of surgical simulation and minimally invasive surgery (MIS), and others at Penn State's Hershey Medical Center, the team has used the software to develop a design for a single MIS instrument that can grasp, cut, pivot and bend around obstructions.
In minimally invasive surgery, which is also known as laparoscopy or endoscopy, a video camera and long slender surgical tools are inserted through small incisions or ports in the body. The smaller incisions cause fewer traumas and decrease postoperative pain, recovery time, and mortality. However, current MIS surgical tools give surgeons limited tactile feedback and dexterity.
Frecker says, "The surgeons complain that using the existing tools is like doing surgery with chopsticks."
Haluck explains that, since most existing MIS tools are single function instruments, the surgeon must constantly withdraw and re-insert new tools. Continually switching instruments can lengthen time in operation and compromise safety.
To find common patterns of instrument exchange, the Penn State team studied videotapes of 29 surgical procedures and identified sequences in which multifunctionality could improve efficiency.
For example, the study showed that exchanges between the scissors and graspers occur frequently, particularly in gall bladder removal operations, one of the most frequently performed MIS procedures. So, both grasping and cutting were incorporated into the design for the Penn State team's new instruments.
One version of the multi-functional tool, small enough to be inserted into a 5 mm incision, is already in prototype. Haluck says that he expects to begin testing it in a laparoscopic trainer box very soon and to conduct animal tests within six months. The tool consists of tiny stainless steel jaws that can function as miniature scissors, with blades the size of rice grains, at the end of a long insertion rod. The jaws can also function as graspers when the surgeon flips a switch on the instrument handle. Using other switches on the handle, the surgeon can also rotate the blades to acute right or left angles to get around obstructions. In a compliant version, still on the drawing board, the surgeon will even be able to make the blades bend to improve maneuvering.
Haluck adds, "This multifunctional approach may eventually be used in cardiac therapy or in colonoscopy, for example, where the surgeon may have to snake an instrument a full meter into the colon in some situations – and snake it out again every time an instrument has to be exchanged. Having a multifunctional tool could reduce these time consuming instrument exchanges."
The new software has been copyrighted and the University has applied for provisional patents for both the compliant and non-compliant versions of the new MIS tool. The work has been described in a paper, "Design of Multifunctional Compliant Mechanisms for Minimally Invasive Surgery," published in the Proceedings of the ASME DETC: Design Automation Conference Symposium on Mechanisms and Devices for Medical Applications held Sept. 9-12, 2001. Ryan P. Dziedzic, master's degree candidate in mechanical engineering, and Frecker are co-authors of the paper. Jeremy Schadler, a master's degree candidate in mechanical engineering, is assisting in development of the non-compliant instrument. Other members of the team at Hershey Medical Center include Dr. Alan Snyder, professor of bioengineering in Penn State's College of Medicine.
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