Here are six ways CAD and 3D printing have come together to drive healthcare forward. Only a few short decades ago, some of these results seemed would have been considered “science fiction.”

Jean Thilmany, Senior Editor

Twenty-five years ago, it became possible to turn a computed tomography (CT) scan or an X-ray into a three-dimensional, handheld medical model that would exactly match a patient’s anatomy. Surgeons could order one of these models from a third-party provider by sending in patient images and getting a handheld model—shaped by human hands from a variety of materials—back within a few weeks.

The widespread advent of 3D printing soon made the sending and the shaping obsolete. Now, doctors who print their individualized medical images have 3-D models in their hands in hours, even in moments, depending on where the printer is located.

That’s one example of the ways engineering technology—including computer-aided modeling and 3D printing—has made hugely helpful strides into the medical field within the past few decades.

And the use of CAD modeling software within medicine continues to evolve even as it becomes more widely adopted within varied medical and biomedical settings. Below, we take a look at the ways CAD continues to make inroads into the healthcare industry.

Surgery guide
Because every patient is different, each surgery differs too, no matter how slightly. For decades in the medical world, surgeons and their professional support teams relied on X-rays, computed tomography (CT) scans and magnetic resonant imaging (MRI) data to plan a patient’s surgery exactly.

Doctors used these guides to study and practice the techniques called upon for that patient’s particular surgery.

But the resolution and 2D perspective of these images could make it difficult to determine the full details of an anatomical geometry. “Subtle abnormalities or hidden geometries can go unnoticed on these flat films,” says Derek Steinbacher former director of craniofacial surgery at Yale New Haven Hospital.

This year, Steinbacher was named the Yale School of Medicine’s medical director for innovation and emerging technologies. In naming the promotion, the school’s directors praised Steinbacher’s use of artificial intelligence and 3D planning for complex and routine facial plastic surgeries.

Today, models of specific patient’s anatomy are often printed in 3D, thanks to the linkage of CAD and 3D printers. The specialized software turns the 2D medical image of the organ, bone, or other part of body into a 3D CAD model that can then be printed, notes Steinbacher.

“Thanks to virtual reality manipulation technology that 3D imaging offers, surgeons are able to plan a surgery using guides and jigs, which are later used during surgery to provide the surgeon with a precise cutting path or accurate drill angles. In many cases, surgeons evaluate several different scenarios long before making an incision,” says Lisa Lattanza, an orthopaedic surgeon at the Yale School of Medicine.

Using this technology, Lattanza, is able to detect indicators for deformity after trauma or congenital deformities. Bilateral 3D renderings are generated from scans that reveal the patient’s skeletal anatomy. Those mirrored images are laid on top on one another, which allow Lattanza to directly compare and evaluate bone topography and deformity in three planes and allow for exact correction as well as to better identify locations for drill guides, cuts, and screws that may be needed.

“This type of technology allows me to perform types of operations I would otherwise be unable to perform or at least could not perform with as much accuracy,” Lattanza says.

The technique has been shown to save time during the operation itself.

A paper in the August 2020 issue of the journal Academic Radiology found that using 3D printed anatomic models in surgical care could cut anywhere from 23 minutes to one hour from the operation itself and cut cost surgical costs by up to $3,720, according to lead author David Ballard, assistant professor of radiology at the Washington University School of Medicine in St. Louis.

“To help hospitals realize these savings, some makers of CAD software provide services that convert anatomical data to CAD files. One example is BioCAD, from SolidWorks. The translation is done by Biomedical Modeling Inc., which makes anatomically accurate 3D reconstructions of the heart, blood vessels, bones, and internal organs,” says Crispin Weinberg, BMI president.

Training, device development
Other models aren’t taken directly from a patient’s CAT, X-ray or MRI; rather, 3D patient anatomy models—based on general-patient CAD data—can be used to more generally guide surgery and to train physicians and other healthcare workers. “Medical device developers also use the models when they create minimally invasive medical devices,” Weinberg says.

The practice of 3D-printed medical models is so widespread that in 2019, the American Medical Association approved four initial current procedural terminally (CTP) reimbursement codes for 3-D printed models. The codes are used to submit reimbursement requests for medical procedures.

“The American College of Radiology and the Radiological Society of North America had been working toward those codes for the changes for some time,” says Frank Rybicki, Vice Chair of quality and safety radiology at the University of Cincinnati College of Medicine

“Medical models and surgical guides have been 3D printed for well over a decade, as niche applications, without CPT codes,” Rybicki adds. “For example, craniomaxillofacial care providers generally accept that 3D printing is valuable and integral to patient care. However, when applying for CPT codes, it became clear that this ‘general acceptance’ lacked peer-reviewed literature to demonstrate value.”

Journal papers like Ballard’s and his colleagues are helping move 3D printing into the mainstream, Rybicki notes.

“The temporary codes are used to define 3D printing’s use in the medical field. Defining the role had been difficult because the technology had traditionally been used for a range of techniques and the uses weren’t well documented,” Rybicki says.

Rybicki founded a RSNA special interest group on 3D printing. In 2019, the society helped establish a registry to gather clinical data on medical 3D printing.

The 3D printing information within the hospital setting collected by the RSNA and ACR will help set formal CPT code nomenclature.

That’s entertainment
Some medical CAD models aren’t actually used for medical purposes. If you’ve seen the movie Hollow Man, for example, you’ve seen digital CAD models from Zygote Media Group, which builds and sells detailed 3D models of the human body based on MRI and CT data.

“Their models include the human skeleton, heart, arteries, nerves, and muscle tissue,” says David Dunston, Zygote executive partner.

“Some Zygote’s customers do use the CAD models to develop biomedicine products. A biomedical company may use 3D heart models to develop stents or a skeletal model to design a brace to straighten a crooked spine,” Dunston says.
“But the models are also used to drop realistic human-looking body parts into video games, commercials, and movies,” Dunston says.

The company’s CAD models have appeared in movies like Hollow Man, in television commercials, and on The Discovery Channel. They’ve also made appearances in a host of university classrooms and corporate training videos, he adds.

Creating body parts
In 2017, Chris Cahill, a New Jersey resident, woke up from a two-months-long coma caused by a brain injury. His brain swelling from the unknown trauma had been life threatening and the patient’s skull itself was infected, says Gaurav Gupta, assistant professor of neurosurgery at Rutgers Robert Wood Johnson Medical School.

“The infected frontal lobe of Cahill’s skull would need to be replaced,” Gupta says.

The surgical team had to custom-make the part to exactly fit Cahill’s skull, he adds. Using Cahill’s CT scans, Gupta’s team 3D printed a model of the skull and a custom-fit implant that would replace the missing piece.

Cahill was nervous about the surgery, but he woke up looking like his old self again.

Gupta pointed out the similarities between the way 3D CAD files and CT scans work. “For 3D printing, 3D CAD models are sliced into two-dimensional graphics files and each layer is then printed one atop the other until the final part is done. CT scans also break 3D images into 2D images each of which is one-slice thick,” Gupta says.

Cahill has been pleased with the results, according to news articles in which he’s quoted as saying he looks “as good as new.”

Printed prosthetics
The democratization of prosthetic design and creation through 3D printing enables millions of people around the world to reap the benefits of the newly popularized manufacturing technology.

The recent ubiquity of 3D printers and innovations in prosthetic design, manufacturing, and distribution offer a viable solution for the millions of people living with limb loss around the world. In the United States alone, close to 200,000 amputations are performed each year, yet, with prosthetics priced from $5,000-$50,000, having one can almost be considered a luxury, according to The Enable Community Foundation, a global network of volunteers who print prosthetic limbs for around $50.

Traditionally, the process of getting a prosthetic limb can take anywhere from weeks to months. Because prosthetics are such personal items, each one has to (or should) be custom-made or fit to the needs of the wearer. However, as 3D printers become more affordable, with some available for less than $200, the possibility of anyone being able to design and print a prosthetic limb in their home or local community could become a reality, according to Jon Schull, Enable board chair president.

In the near future, prosthetics will be seamlessly integrated into people’s everyday lives with minimal effort. New 3D scanning and body modeling technologies from companies such as Body Labs enable people to 3D scan their limbs and have prosthetics modeled after them, making for a more natural fit and appearance.

Technological developments from innovators such as Hugh Herr—a rock climber an MIT biophysicist—have introduced new abilities, including propulsion sensors and sophisticated algorithms that work together to automate more natural joint movement.

“The development of predictive movement for prosthetics will make it so people won’t have to think hard about controlling the device. Soon, prosthetics will move with more fluidity to mimic natural movement, and people will be able to control them in part with their brains and bodies through direct natural touch input systems,” Herr says.

New body parts for transplant
From prosthetics to actual body parts: researchers are at work on ways to actually print living tissue from CAD files.
In recent years, 3D bioprinting has made huge strides toward the goal of printing organs that can be successfully transplanted into humans. “While that’s still far in the future, the method continues to be studied and advances can lead to new and improved treatments for conditions such as spinal cord injury, Alzheimer’s disease, Parkinson’s disease, brain cancer, and more,” says Steinbacher of the Yale School of Medicine.

The 3D printing of living cells follows standard 3D printing methods with a few twists. The printer, following a CAD file, lays down layer upon layer of material to build a shape. Instead of metals or plastics, bioprinters use bioinks as their materials. These contain living cells amid viscous materials like alginate or gelatin. “The cells are often built upon scaffolding to support and protect the cells,” Steinbacher says.

As these examples show, the intersection of healthcare and 3D printing is only in its first stages. It’s not the stuff of science fiction. 3D printing, CAD, and medicine have come together to bring us a better quality of life. Even 20 years ago, these results were unthinkable.

Cahill, as he goes about his days, is thankful times have changed and 3D printing has made the inroads it has into medicine.