Point-of-care additive manufacturing provides complex scoliosis models

March 27, 2021

Mayo Clinic has the largest point-of-care additive manufacturing facility in the United States. The 8,000-square-foot space provides highly accurate 3D-printed anatomic models and surgical guides for Mayo's surgical specialists.

"Our manufacturing facility is located in our hospital within the Department of Radiology, so we can easily interact with surgeons. We're able to move rapidly from customized CT and MRI protocols to the creation of a patient-specific, life-sized 3D-printed models or devices," says Jonathan M. Morris, M.D., a neuroradiologist and medical director of the 3D Anatomic Modeling Laboratory at Mayo Clinic in Rochester, Minnesota.

The models are valuable presurgical and intraoperative tools for the treatment of adults with complex scoliosis. "Holding a 3D model makes it much easier to understand complex anatomy, particularly in revision surgeries or in patients with congenital adult scoliosis," says Jeremy L. Fogelson, M.D., a neurosurgeon specializing in spinal care at Mayo Clinic in Rochester, Minnesota. "When we look at 2D images on a screen, we see one slice at a time and then have to do a lot of mental juggling to reconstruct those slices into a real-life image."

Dr. Fogelson cites a case in which a 3D spinal model indicated that an adult scoliosis surgery would be more complex than he initially thought. "The patient was a man with very large bones. An X-ray can't show you bone size," Dr. Fogelson says. "But when I held the model, I realized we needed to operate over two days in order to safely work through that much tissue."

Mayo's model-manufacturing process starts with CT and sometimes volumetric MRI, using imaging protocols designed by Mayo Clinic radiologists specifically for 3D printing. A Mayo radiologist evaluates the accuracy of the imaging data before the model is produced.

"Our patient-specific models aren't developed only according to an algorithm created by an engineer who doesn't fully understand anatomy," Dr. Morris says. "The biomedical engineers in our facility are part of the clinical care team, routinely working with radiologists and surgeons."

The imaging data is segmented, and the model is created using several 3D printers. "No single printer does it all — we have the capability to do additive manufacturing using all seven ASTM standards," Dr. Morris says. "The life-sized model we give to the surgeon is exactly what the surgeon is going to find during the patient's procedure."

Mayo Clinic launched its additive manufacturing facility in 2005. Mayo's campuses in Arizona and Florida also have 3D anatomic modeling laboratories as of 2020, with collaboration occurring enterprisewide.

As a tertiary center, Mayo Clinic performs a high volume of revision surgeries for adults with complex scoliosis. The 3D imaging protocols use advanced techniques such as iterative metal artifact reduction and multispectral energy to reduce artifacts from metal implants. "Without those techniques, we don't get an accurate model," Dr. Morris says.

The 3D models can enhance the safety of revision procedures, which are often performed in the absence of anatomic landmarks removed during the patient's original procedure. "It can be challenging to determine optimal screw placement in a revision spine with bone grafts," Dr. Fogelson says. "Examining the 3D model before surgery — rotating it and looking at the side of the spine that will remain covered during the surgery — guides our screw locations and trajectories. We also save time in the operating room because at times we don't need additional imaging or technology to guide screw placement."

Mayo Clinic performs 3D printing in numerous materials, including sterilizable materials for use in the operating room. Planning is underway for printing on titanium through Mayo Clinic Engineering.

"That will allow us to innovate and serve more patients with unique needs," Dr. Morris says. "Our goal is to provide complex, customizable models and guides that benefit our patients, who come to Mayo for solutions they can't get anywhere else."

For more information

3D Anatomic Modeling Laboratories. Mayo Clinic.