The Cranial Implant Challenge

Cranial implants are generally only necessary when patients have suffered accidents or serious illness. The attending doctors face a major task with each procedure: there is no room for error while working on an open skullcap, and they must also ensure that following the procedure the patient is able to live a life free of discomfort.

This makes it all the more important that suitable implants are used. An exact fit is a prerequisite to ensure the procedure will be successful long-term. Slovakian company CEIT Biomedical Engineering, s.r.o. relies on EOS additive manufacturing (AM) technology to provide doctors with bone replacement material for their patients as quickly as possible.

Additive Ambitions

The basics of medical implant manufacture have been, until recently, control technology, the relevant machine tools, and often manual work carried out during the operation itself. Yet, these technologies can lead to some problems. Despite the relatively fine control offered by CNC machines, its design limitations made it impossible to manufacture certain organic shapes. In addition, the process is relatively drawn out and expensive—particularly in the manufacture of custom-made parts.

The team at CEIT Biomedical Engineering was well aware of such issues. CEIT is a spinoff company of the Technical University of Košice (TUKE), and was created for the purpose of promoting additive manufacturing in the medical sector. Assoc. Prof. Radovan Hudak, Ph.D., managing director of CEIT, explained that as a company with close links to the university they were familiar with AM technology, but wanted to explore its potential for implantology and at the same time develop solutions for patients that were both helpful and economical.

How could additive manufacturing contribute to the manufacture of a custom-made, perfectly fitting cranial implant for surgery? CEIT felt it was necessary to explore the limits of the technology and its potential application as well as discovering the optimum process and finding a suitable material. Precision, reproducibility, and surface quality were all high up the list of specifications, along with a production process that was as free as possible from production errors. Finally, state certification for cranial, jaw, and facial bone implants was required.

Exploring with EOS

Following intensive research, Hudak's CEIT team decided on AM leader EOS as its technology provider, while opting for a titanium alloy as the starting material. “We took a year to explore the market and to analyze what was available,” confirmed Hudak, describing his detailed search for the right solution. “EOS and its EOSINT M 280 convinced us by meeting the core criteria, such as experience, market success and penetration, as well as offering the complete package. In addition, a number of clients confirmed their satisfaction with the system itself.”

The decision opened a way to meet the required technological criteria. It enabled manufacture of extremely thin walls with the necessary uneven surface geometries. In addition, the CEIT team was now able to introduce cavities to the implants—such as shapes comprising complex hollows or canals. Lattice structures became a key element in the range of possibilities.

For the actual manufacturing process of the first implants, all that was needed was a suitable patient and their medical records. In this specific case, the task was to produce a piece of the cranium approximately 15 cm. in size from the titanium alloy Ti-6Al-4V—a biocompatible standard alloy in medical technology with excellent mechanical characteristics. The team used the results of a computed tomography (CT) examination, where all the necessary contouring information was recorded in detail. The data transformation to a CAD program and the design and manufacture of the implant all took place at CEIT.

A good prognosis for AM

The first success was at the technological level: CEIT was able to successfully implement the production process for both the series production of standard implants and the production of one-off, custom implants. The team was also able to produce the desired lattice structures by means of additive manufacturing. The first patient-specific manufactured implant weighed just 63 g, with a thickness of only 1.5 mm, and the hollow structure enabled the integration of micro-sensors for the recording of medical data inside the implant.

Even greater success for the company followed with the registration of the implant for cranial, facial, and jaw applications with the Slovakian State Institute for Drug Control (SIDC). This resulted in official EU-wide approval. Negotiations with the largest national insurers over cost coverage also proved successful. One reason for this is the fact that the sales price is in line with the market. The implant benefits from higher precision contouring and a lower error rate in production.

Hudak concluded, “We were able to meet all of our challenges and achieve our goals. The great thing about it is that we can give people a higher quality of life thanks to the precision fit of the implants. The accurate contouring has a positive effect on recovery, long-term compatibility and the final visual result. When the wound has healed, the exact insertion of the implant makes the evidence of the procedure far less noticeable. This aids the psyche of the individual significantly. Additive manufacturing is support for both body and soul—a truly innovative technological masterpiece.”