Austria´s Salzburg University Hospital has 3D printed a polyether ether ketone (PEEK) cranial implant in-house and implanted it into a 55-year-old man suffering from a skull deformity. Although PEEK has been widely used for craniomaxillofacial implants, material extrusion 3D printed implants as the one done here on a Kumovis R1 are rarer. Furthermore, a PEEK implant is usually printed off-site by an external service company. In this case, it was 3D printed in the hospital by the hospital. This could potentially upend a lot of healthcare spending and demonstrates the possibility of 3D printed implants at the point-of-care.
3D Printing to the Rescue
Salzburg resident Rainer Trummer suffers from craniosynostosis, in which bones ossify in childhood, leading to deformities and negative social consequences. While the soft heads of babies begin to close around two-years-old through bone fusion, craniosynostosis occurs when bone fusion takes place earlier than the brain is completely formed, leading to voids. In other areas, growth could be more regular, resulting to parts of the head being shaped irregularly. In severe cases, brain development or function may be inhibited. Many children also suffer because they are perceived as different, with Trummer noting that he was teased as a child because of his condition.
Trummer also found it difficult to find the right doctor and an early procedure had been cancelled due to the COVID pandemic. It wasn’t until he met with Professor Alexander Gaggl, head of the Department of Oral and Maxillofacial Surgery at the University Hospital of Salzburg. “I had known Professor Gaggl since another operation in 2012 and had complete trust in him,” Trummer said.
Gaggl’s team used Oqton’s D2P and Geomagic Freeform to take CT scans and transform them into a file for a custom implant. The custom PEEK device was 3D printed with Evonik´s VESTAKEEP i4 3DF PEEK, an implant-grade filament. A semi-crystalline thermoplastic, PEEK offers high heat and chemical resistance, as well as high strength, making it widely used in the most demanding industrial and aviation applications. It is also biocompatible and radiolucent. This specific variety has been approved for long-term implantation in the body, also conforming to specific ASTM guideline for implantable PEEK polymers, F2026.
As a first step Gaggl’s team implanted a balloon in Trummer’s skull, filling it with 250 ml of saline solution over time in order to stretch the skin so that it could accommodate the implant. The 12 cm by 3 cm implant was printed in ten hours, while the surgery itself took six. Trummer said that, “I don´t feel like I have an implant in my head, but now I have a completely normal head. It´s like a miracle for me.”
“We are thrilled for Mr. Trummer and the relief this procedure has given him, and deeply indebted to the talented surgeons and staff at Salzburg University Hospital who brought together for the first time our unique software, hardware, and materials technologies in a point-of-care hospital setting to address his specific needs. We believe that this success provides a real-life demonstration of the potential for enhancing orthopedic outcomes through the use of comprehensive digital manufacturing technologies in a hospital setting. Our focus on point-of-care implementation of these integrated technologies is a key priority for our company, and one that we believe will bring significant benefits to patients around the world in the years ahead,” Jeff Graves, 3D Systems CEO, stated.
3D Printing for CMF Implants
With craniomaxillofacial (also referred to as CMF) implants, a specific design is of the utmost importance because of the need to restore function and aesthetics in an area that can have an outsized impact on a patient’s life. Due to this, 3D printing with powder bed fusion (PBF) and vat photopolymerization has been previously used for these applications. Generally, vat polymerization is not currently seen as having the strength needed for these kinds of applications, a limit that may change in the future. If it does, there are some questions around biocompatibility and the photoinitiators.
More common is PBF implants with PEEK. Here, the issue is that there is a need for powder in the build to support overhanging structures and cavities. If a polyamide powder were used for less regulated purposes, it would be possible to recycle it. However, in the case of medical applications, recycling may not be permitted. As a result, the economics of PEEK PBF implants do make sense if the volume is high and constant enough, but other parts, such as screws and plugs, may be more financially viable than CMF implants, given the geometry.
Meanwhile, material extrusion is rare for these implants currently, generally seen as a technology that can not achieve the fine details that PBF does. However, material extrusion does only print what is needed. A PEEK material extrusion 3D printer is also much more affordable and easier to install and maintain than a high temperature PBF system. While an FDM 3D printer unused just sits there depreciating, the PBF system is six times more expensive and is plotting to bankrupt you even when it is running, let alone when it’s not being used.
3D Printing at the Point of Care
3D printing of medical devices at the point of care is poised to grow. And material extrusion would be the most cost effective way to do that both in terms of the up-front and running. In metal implants, we can see that the Hospital for Special Surgery has a manufacturing center in-house, run by orthopedic implant company Lima Corporate. This means that the implants are 3D printed at the hospital, but by an external firm with the expertise to do it. The U.S. Department of Veterans Affairs has its own metal printer, as well, which allows the division to print its own special cases and implants. Both examples could upend a lot of healthcare spending.
In cases where a hospital has a lot of volume, it can really make sense to print on-site and with a partner. The Hospital for Special Surgery is kind of unique, however. It performs 32,000 surgeries a year, almost all of which are knee or other orthopedic procedures. The high volume and degree of specialization, together with the familiarity orthopedic surgeons have with PBF implants, makes the this group the exception, rather than the rule. I can see how France, Germany, or the U.K. could have several similar hospitals.
But, to give you an example, in the Netherlands there have been “300,000 hip and knee arthroplasties performed since 2007.” To fill 3D printers consistently for a country of 17 million, it may make sense to have one hospital specialized in printing on-site metal implants for these procedures in the country. Of course, there are other examples in spinal fusion and more but even for the wealthy slices of the world and in places with high population density we shouldn’t assume that the market is endless.
However, polymer material extrusion is much more accessible, meaning that there may be more hospitals able to try it. Especially when we start looking at 3D printing for orthopedic trauma or very specialized cases, it may very well make sense to have 3D printers scattered at a lot of hospitals. I’m particularly bullish about post-operative braces, custom medical devices, new innovations in trauma care, and the ability of 3D printers to make specific new geometries to drive growth in this area.
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