3D simulators give surgeons a head start
Models eliminate much of the guesswork
Bernice Belcher couldn’t get out of bed.
It wasn’t that she was tired – she’d had a good night’s sleep. But every time the 77-year-old from Columbus, Ohio, tried to get up, she became so dizzy she had to lie down again.
That’s how she eventually found herself in consultations with surgeons who told her she needed an artificial heart valve, to be done by open-heart surgery. They had abandoned the thought of less-invasive surgery – transcatheter aortic valve replacement, or TAVR, because Belcher’s aortic root, where the body’s main artery meets the heart, wasn’t long enough to have an artificial valve implanted using a catheter.
“The next option was to go in,” she says.
Belcher’s surgeons decided on the best way to proceed, thanks to a 3-D model of her aorta. Such modeling can take some of the guesswork out of surgery before a single cut is made.
Scott Lilly, an interventional cardiologist at Ohio State University Wexner Medical Center, operated on Belcher. “We talk about patient care and individualizing care,” he says. “This is a small but a real and successful example.”
Using CT scans that are manipulated via special software, a team of engineers creates a model fashioned from flexible materials that re-create the texture of the aorta and its surrounding structures. Then the model is loaded into a heart simulator: a box filled with pumps and bloodlike fluid.
The engineers watch as simulated blood flows through the printed aorta, and they monitor blood flow, pressure and other effects using lasers and highspeed cameras. Next, they insert the replacement valves that would be used with a transcatheter procedure, for example, and see what changes. Computer models predict how blood flow would respond to each patient’s unique anatomy.
The process helps doctors decide how to approach the surgery and which valve to use – or, in the case of patients such as Belcher, whether to move forward with the surgery at all.
“It’s fantastic for patients,” Lilly says. “It’s an example of scientists and doctors working together to do something that’s really cool. We’re not in silos anymore.”
Those collaborations are becoming more and more common, especially as 3-D printing becomes more affordable. Such technology can be used to create personalized implants such as vertebrae or to fabricate just-right tools for use in the operating room. Its use in surgical planning may be less dramatic, but it’s no less innovative.
Vidyadhar Upasani, a pediatric orthopedist at Rady Children’s Hospital in San Diego, uses 3-D printing to help plan intricate bone procedures to treat, for example, slipped capital femoral epiphysis, the most common hip disorder in adolescents.
The condition occurs when the head of the femur slips on the growth plate of the hip, causing pain, spasms and limited range of motion.
It can be corrected, but surgery is tricky: In the operating room, surgeons become sculptors, cutting the bone, shaping it to perfection and resetting it against the hip.
That’s where Upasani’s models come in. Developed by his surgical team and bioengineers from the University of Cali- fornia at San Diego, the process relies on CT scans to create a 3-D image of the femur. Upasani then prints it and performs a dry run of the surgery.
“We use the saw that we usually use in surgery, and the usual plates and screws,” he says. “It adds that extra dimension.” During the practice surgery, the team figures out exactly what shape they’ll need to achieve with the bone and which steps they need to take to get there.
There’s another benefit to the practice: Surgeons rely on real-time imaging from X-ray fluoroscopy to help visualize the complex structures they’re working with. This exposes the patient and the surgical staff to radiation.
“Everyone in the room is exposed,” Upasani says. “We’re all wearing lead for protection, but still.” More-accurate surgeries mean the team can rely on fluoroscopy less.
Upasani knew 3-D-assisted surgeries took less time, but he wanted to know how much less. So he conducted a controlled study and published the results in the Journal of Children’s Orthopaedics last year.
For the study, he performed 10 proximal femoral osteotomy surgeries to correct femur deformities in kids with hip disorders. Five used a 3-D model; five didn’t. Five more surgeries were performed by other surgeons who didn’t use a model.
Surgeries that were planned with a model lasted less time were done much more quickly, and they used less radiation.
Although Upasani would like to see 3-D modeling used in more surgical facilities, he notes that the models are not covered by insurance. Even though the technology is becoming less and less expensive, it’s still not common in many medical facilities, and not all facilities have access to engineers on staff.