Published 3/1/2007
Peter Pollack

Will computers replace cadavers?

Virtual reality project debuts at Annual Meeting to mixed reviews
Surgical training has always depended on using cadavers to enable residents to perfect a procedure before performing it on an actual patient. But at the 2007 AAOS Annual Meeting, a new device debuted that could revolutionize surgical training.

Tucked away in a private room at the San Diego Convention Center was the Virtual Reality Arthroscopic Knee Surgery Simulator Project—an initiative that was first proposed a decade ago, and one that is steadily proceeding toward clinical trials, perhaps before the end of this year.

The project is an ambitious attempt to create a paradigm shift in the way orthopaedic surgery is taught, using modern computer and electromechanical technology to place the student in a simulated working environment so that he or she can perform an arthroscopy on a realistic virtual knee.

“What we hope to do is enable residents to train and reach an acceptable proficiency level before they go into the operating room to do arthroscopic surgery on real cases,” explained W. Dilworth Cannon, MD, chair of the project’s content development group.

“I think it’s the way to go,” said Donald H. Johnson, MD, after trying out the simulator. If anything, he wishes the project could proceed more quickly. “I’m sick of using cadavers,” he laughed.

Building a new paradigm
To produce the working design, Dr. Cannon and his team partnered with Touch of Life Technologies (ToLTech), best known for its work on the Visible Human Project® (VHP)—an initiative undertaken by the National Institutes of Health to create complete, detailed, three-dimensional models of normal male and female bodies. To achieve that goal, VHP sectioned the male human body into 1 mm intervals, and the female human body into 0.33 mm intervals.

Although the degree of resolution attained in the VHP was considerable, the AAOS group wanted the simulation to have an even higher level of realism. Advances in technology enabled the ToLTech team to section the knee into 0.1 mm intervals, resulting in a 3-D model with 100 times the resolution of the male VHP specimen.

Once the software model was in place, the next step was to build a unit that could serve as the interface—a set of physical tools that would work and respond like the surgical instruments and knee in a real procedure. Fortunately, available technology had kept pace with the needs of the development team, and they were able to procure a pair of haptic devices “off-the-shelf” from SensAble Technologies of Woburn, Mass.

A haptic device uses tiny motors to provide tactile feedback to the operator. In other words, if the probe on the virtual reality unit is used to palpate the lateral meniscus, the user will “feel” the tissue as though he or she were actually performing the procedure. This allows the resident to develop a touch for the surgery that previously couldn’t be learned without a live patient or a cadaver.

“The feedback part is pretty good,” commented Andrew M. Wong, MD. “I didn’t even think they’d be able to have that, so that was pretty interesting.” Still, he admits that the team has some work to do before sending the unit for validation.

“There are still some bugs that need to be worked out,” he said, when asked to give an overall assessment of the project, “but I think it’s certainly going to play a role in teaching people how to do arthroscopy.”

A virtual mentor
Perhaps just as integral to the simulator as the high-resolution graphics and the mechanical design is a special program called the mentor. The mentor oversees the student’s progress, while simultaneously offering advice and critique. In a small way, the mentor takes the place of a human teacher, enabling residents to practice with the unit on their own outside of an operating room. The mentor program also functions as a gateway, allowing students to progress to a new technique only after they are deemed proficient at the current one.

Does this imply that someday, surgeons will be trained primarily by computer? ToLTech’s Karl Reinig, PhD, believes that the experience and intelligence of a human trainer would be difficult to replace, but he is quick to point out how the simulator can assist physicians and residents alike by providing precision feedback.

“The simulator’s advantage is in its objectivity,” he explains. “An expert looking over a student’s shoulder is guessing how much force the student is exerting, until the little line of torn-up cartilage is visible. The simulator shows exactly how much force the student is putting on at all times, and we can actually get more quantitative. That’s the purpose of the mentor.”

Validation, then commercialization
Validation is planned to take place at eight residency programs across the United States, each of which will be given the chance to use the simulator for 45 to 60 days. Third-year residents will be divided into test and control groups and asked to perform a diagnostic arthroscopy. Internal and external recorders will be used to record the procedures. A group of physicians will rate the students according to a set of standards, and the results of both groups will be compared.

Assuming the unit passes validation, the development team plans to expand the concept to other joints and pathologies, while making the current device available as a commercial product.

A major concern is affordability. Several surgeons expressed concern that once the simulator is available, it may be so expensive that only the largest institutions will be able to afford it. Although commercial availability is several years away, the affordability issue is already being addressed.

“When the simulator is complete, the AAOS will not hold copyright or ownership,” explained Howard Mevis, AAOS staff liaison to the development group. “ToLTech has ownership and is responsible for setting prices for the simulator. We expect that orthopaedic departments will be able to purchase with annual maintenance fees or lease the device for an annual fee plus hourly usage and annual maintenance fees. The purchase and lease prices have not been set.”

“I believe that the leasing option, which brings with it the need to pass it along to other programs, will greatly reduce the burden on any one program,” agreed Dr. Reinig. “It will require program directors to schedule their residents so they can all get their simulator training during the one-, two-, or three-month period that the simulator is at their facility each year. But if they are willing to do that, they will automatically receive the latest upgrades each year and greatly reduce their share of the hardware costs.”

In just a few years, residents may be learning complex knee, shoulder, and elbow techniques through the wonders of virtual reality. “I can only see an upside,” said Dr. Johnson. “There’s a huge benefit to learning to move around in the knee, triangulate, and perform basic skills before setting foot in an operating room.”

Jay Mabrey, MD, chair of the AAOS virtual reality task force, tests the arthroscopic knee surgery virtual reality simulator.