Taking a new medical device idea from design through development and to regulatory clearance is no easy task. Taking a design that incorporates innovations in metal and polymer additive manufacturing is harder still! This story is not just about one innovation, but many: To deliver this new 3D printed spinal fusion solution the team at restor3D not only invented a new product but also had to reinvent processes, testing, methodologies, and materials.
Cambre Kelly, PhD, and VP of Research and Technology, restor3D, and her team had identified unmet needs in spinal fusion surgery, not only with the implants in use but with the surgical tools to complete the operation. The team felt that 3D printing could assist not only with the surgical procedure by using single-use, sterile tools, but with post-surgical recovery times through the development of complex porous metal lattice structures to promote bone growth into the implants.
Materials were the first concern. Kelly explains that 3D printed implants have evolved across the years from metal, through to research using PEEK, and now to titanium. Research by Kelly and others at Duke University into mechanical properties of porous lattice structures using metal powder bed fusion had resulted in the innovation of a gyroid geometry based on continuous sheets. This new style of medical 3D printing had the potential to improve surgical outcomes and recovery. The innovation and research already completed for this project continued into mechanical properties of the implants, and how to optimize output of metal 3D parts.
“How do we study fatigue life not only in compression, which was and still is the dominant loading mode seen in literature, but also looking at torsion and tensile fatigue properties of these implants? Then also looking at PBF post-processing and post-processing as well,” says Kelly.
For the surgical tools, SLA photopolymer material had to be developed that had to be tough enough for surgical procedures yet also had radiodensity so surgeons could see the instruments under x-ray.
“We were trading off toughness and trying to find that Goldilocks Zone that gave the right mechanical properties in the right optical properties as well,” says Kelly.
The team was required to innovate a new formulation of photopolymer materials that met all these needs and could still be sterilized for use. The result is 3D printed instruments that are delivered as a small, custom, single-use, sterilized toolkit for each operation.
Throughout the presentation Kelly points out that the advantage of additive manufacturing for medical device design not only produces end-use parts but also enables rapid and frequent iteration of the designs.
“We’re always prototyping, testing, preliminarily testing, iterating, and moving through, seeking clinical feedback from the key opinion leaders that we work with in this space, [to] move through a development phase,” says Kelly.
More innovation on the process qualification phase also became a necessity, and then the same for validation and verification, before submitting the 510(K).
“[At first] we had print failure after print failure. Trying to take a desktop system and scale it up for production. Trying to figure out how to do process qualification around these. How do you do IQ, OQ, PQ on systems like this? How do you optimize the print area that you have to produce the most number of parts with the most uptime? Then how do you scale that up?” says Kelly.
Ultimately the restor3D team encountered success with the commercial release of this new spinal fusion solution. Watch the presentation now to understand how this was achieved.
Find out more about medical applications of 3D printing and meet leaders like Cambre Kelly at the upcoming AM Medical Summit, November 1-3, 2022 in Minneapolis, Minnesota.