Prosthetics Digitally measured, bio-based printing

The NaRo-3D research project demonstrates how prosthetic stems can be manufactured in a more climate-friendly and efficient manner. Bio-based, 3D-printable materials and a fully digital manufacturing process separate the process of taking patient measurements from production, thereby offering benefits not only in areas where there is a shortage of qualified personnel.

According to ATscale, an organization affiliated with the WHO, approximately 65 million people worldwide live with a limb amputation. An estimated 1.5 million people—some of whom have undergone multiple amputations—are added to this number each year. Only a fraction of those affected receive care. In low- and middle-income countries, according to WHO data, only 5 to 15 percent of those in need have access to an adequate and properly fitted prosthesis. A key bottleneck is the shortage of trained specialists, who are often available only in major cities.

This is precisely where the NaRo-3D project comes in, a collaboration involving the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA), the biomaterial manufacturer Tecnaro, and the orthopedic company DOI ortho-innovativ. The project was funded by the Federal Ministry of Agriculture, Food, and Home Affairs (BMLEH) through the project management agency Fachagentur Nachwachsende Rohstoffe (FNR).

High-Tech Biomaterials Straight from the Printer

Tecnaro processed bio-polyolefins, bio-polyesters, bio-polyamides, bio-TPU, and cellulose derivatives with various fillers and additives to create 3D-printable composites. According to the manufacturer, these materials demonstrated good melt flow properties—which are important for the production of filament-shaped monofilament—as well as mechanical properties that, in some cases, exceeded those of comparable petroleum-based products. According to the project, two variants even achieved the properties of high-performance materials such as titanium or carbon fiber.

In DOI’s printing tests, two materials proved to be particularly suitable: a biopolyester with 78% bio-based carbon content and a 100% bio-based biopolyamide. A transparent filament made from cellulose derivatives and biopolyester, which has a bio-based carbon content of 46%, was also well-suited for the production of test shafts, according to the manufacturer.

From Imaging to Printing

The Fraunhofer IPA developed a virtual abutment design platform for seamless, digital design and manufacturing. This platform utilizes MRI, laser scanning, and ultrasound imaging techniques, and uses the data from these methods to create CAD and finite element models of the residual limb and the abutment. Using the finite element method, load-bearing capacity and comfort performance in interaction with the stump can be determined, and the geometry and wall thickness of the prosthesis can be optimized. The project describes the fact that, in addition to volumetric stresses, the shear stresses of the stump are also taken into account as a novelty in prosthetics. Feedback from long-term prosthesis wearers regarding prostheses made of bio-composites has also proven to be positive.

Digital manufacturing remains a niche market for now

Instead of making a plaster cast, pouring casting resins into it, and spending hours on manual labor, measurement data could theoretically be processed worldwide and would not depend on local expertise. This is particularly relevant in regions with a shortage of skilled workers.

However, the technology is not yet widely used. According to industry estimates, only about 10 to 20 percent of orthopedic technology companies in the DACH region operate at least partially digitally; less than 5 percent of prostheses are actually 3D-printed. According to its own statements, the federal government does not have reliable statistics on the use of this technology. In addition to regulatory requirements under medical device law and increased investment needs for scanners, software, and printers, reimbursement structures that remain unclear are also considered barriers to adoption.

Relevance for Health Care in the Global South

“We hope, not least, that the project results will help improve orthopedic care in many countries through optimized digital approaches,” says Karl-Heinz Trebbin, master orthopedic technician and DOI managing director. He himself has many years of experience in providing care to amputee patients in South America, Africa, and Asia. However, digital methods should “not replace orthopedic expertise, but rather complement it in a meaningful way.” Ideally, this would leave more time for individualized patient care.

The Fraunhofer IPA aims to make its virtual measurement platform available to users such as medical supply stores and orthopedic technology companies. “Since specialized programming knowledge is currently still required to use the platform, we are supporting medical supply stores with targeted pilot projects to help them successfully integrate these innovative digital processes into their internal workflows,” emphasizes project manager Dr.-Ing. Okan Avci of Fraunhofer IPA.

Tecnaro, for its part, intends to move quickly to bring the new composite materials to market, and its sights are set on more than just 3D-printed orthotic and prosthetic applications. The company also plans to offer injection-molded end products with high heat resistance and impact strength for other industries. The monofilaments are expected to be available shortly through the distribution partner Albis Distribution. The Final report of the project can be viewed on the website of the Agency for Renewable Resources (FNR).

This article was first published on our sister site www.healthcare-digital.de.