A Technical Review of Additive Manufacturing in Orthopedics
(Guest article written by Brian McLaughlin, Amplify, Inc.)
The History of AM in Orthopedics
Additive Manufacturing (AM), or 3D printing, has been used in Orthopedics for many years, from companies such as Pipeline Orthopedics (now part of Stryker) to Exactech, among many others. The technology has been more widely used outside the US by companies like Adler Ortho and Lima (Lima reports that they have implanted over 100,000 3D-printed acetabular cups to date). In fact, AM has been in use by many companies for well over 10 years now, to produce products ranging from custom and standard implants to complex instrumentation. It has been seen as a technology that was out of reach for many product companies due to cost and complexity, where only those with the deepest of pockets, and/or by happy coincidence, the right skill sets, could take full advantage. However, with the technology and machines becoming more robust and more readily available, use of AM within Orthopaedics is steadily growing. Yet hurdles remain despite the many advantages, clinical, operational, and financial, afforded by the adoption of this technology.
The Two Fundamental Technologies
The two primary technologies used for Additive Manufacturing of metals are Electron Beam Melting (EBM) and Laser Sintering. Only one company provides EBM, Arcam, now part of GE Additive. There are a handful of companies providing Laser platforms, such as EOS, Concept Laser (also part of GE Additive), Renishaw, 3D Systems, and SLM Solutions, with a few more on the horizon.
The primary material used for implants is Titanium, Grades 5 and 23 primarily. Cobalt Chrome is another material that is available on both platforms, however mostly utilized with Laser processing. Laser platforms also offer access to other materials used in Orthopaedics, including 17-4 Stainless Steel, which is widely used for instrumentation. Outside of Orthopaedics, depending on your application, several other materials are available for AM production, such as Aluminum, Titanium Aluminide, Inconel, etc. Subsequently these platforms enable a broad range of productive possibilities that markets have only recently begun to exploit on an industrial scale.
Choosing a Technology
Each technology offers its respective productive attributes, but perhaps the most widely discussed aspect of these attributes is resolution – i.e. how fine a surface finish is possible for the parts right out of the machine without the need for secondary processing. While resolution can be an important factor for a given application, generally speaking, finer resolution is not necessarily better than rougher, and vice versa. Therefore, for any specific application, the real question should be, what level of resolution will produce the greatest clinical benefit, and will the design stand up to the physical testing required to obtain the product clearance? So how do each of these technologies, EBM and Laser, differ with regards to this attribute, and how will that difference impact outcomes in different clinical applications?
There are many studies done by universities and companies that show that show surface roughness at the microscopic level promotes bone growth. There are also studies that show that there is an optimal pore size for a lattice structure or lattice layer that supports bone ingrowth. While both technologies can allow for designing these types of structures, one technology (EBM) provides more surface roughness than the other (Laser), which could ultimately provide a better clinical environment for bone attachment and ingrowth. The difference between the two technologies however on a competitive basis may not tell the full story for using additive for a product. (That will need to be covered in a future article)
When Rough in Right
In the orthopaedic context, lower resolution can be advantageous for patient outcomes. Clinical studies have consistently shown that surface roughness at the microscopic level promotes bone growth. Similarly, there is consistent clinical evidence that there is an optimal pore size for a lattice structure or lattice layer with regards to promoting bone ingrowth. While both technologies can allow for designing these types of structures, one technology, EBM, provides more surface roughness than the other (Laser), which could ultimately provide a better clinical environment for bone attachment and ingrowth.
When Smoother is Better
Conversely, in situations where in-growth is not relevant or required and interaction with soft tissue is a factor (e.g. bone replacement), a smoother (i.e. higher resolution) surface will be preferable. In this case, one might get the desired surface condition more efficiently with laser than with EBM. To be clear, the same result can be achieved via EBM, but with slightly more secondary machining or polishing of the device to the desired degree of smoothness.
Efficiency is a Factor
Fully understanding the differences between the two technologies, however, with regards to choosing a specific pathway for a given product, would also require an understanding of production capabilities from an efficiency perspective. With EBM, several layers of components may be printed in a single build (think stacking), whereas only a single layer is possible with Laser systems. So where this aspect may not be a factor with larger devices or components, it will be a material consideration for smaller products that could be stacked for greater production efficiency. Similarly, polishing scenarios notwithstanding, EBM production typically also reduces the number of secondary processing required as compared to Laser systems for reasons that have to do with how the internal conditions in the chamber during the build process. Subsequently, on average, EBM may be the better bet for most orthopaedic applications.
Management of risk is a common theme in Orthopedics, so this topic is no surprise. However, rather than focusing on end product safety, which is well understood across the industry, we will confine our focus to the production environment. During site visits or in supplier marketing materials showing images of AM facilities, you may have seen people wearing full protective gear when working in, and around AM machines. This precaution is due to (Titanium) powder management, and it is somewhat different between Laser and EBM systems. The powder size for Laser is often between 25-45 microns, while powder size for EBM is between 45-105 microns. Generally speaking, Titanium powder at the Laser specification can be explosive and needs to be managed differently than the powder for EBM, which is not considered explosive.
Recent Technology Trends
Over the past six to twelve months , particularly with spine products that were FDA-cleared and Additively Manufactured, it seems that the majority, if not all, were manufactured via Laser. While I may be somewhat biased towards EBM, given my experience with, and knowledge of the technology, I suspect there is another dynamic driving this trend: Access to the technology – there are simply more companies providing Laser services than EBM services.
Exactly why the market has developed this way is open for debate, though it likely has something to do with having more laser platform suppliers in the space (as opposed to just one or two for EBM). But that very fact further complicates the analysis in that different AM service bureaus offer different platforms, and FDA clearances are linked to the specific platform on which it was cleared. Of the providers with which I am familiar, a few are EOS shops, one is Concept Laser, one has (3) different Laser platforms, and even then, they only use certain machines for certain types of materials, and so on. In this environment, OEMs have to determine which platform they want to use while also finding a supplier with that same capability. In addition to the core Additive capability, especially with Laser-based systems, OEMs have to consider what else is on offer in terms of downstream processing, i.e. machining, finishing, cleaning, packaging, etc. (Despite the tremendous supply chain advantages afforded by Additive Manufacturing, the path still requires some secondary suppliers almost all of the time, so useful to keep that in mind.)
Opinion on the Best Technology for Orthopedics
I have an interesting perspective on our industry, having previously been very involved with the AM Group at DTI/Arcam, which was recently acquired by Oerlikon, as the Business Unit Manager and more recently working on behalf of an OEM needing AM and secondary services from outside contract manufacturers. At the OEM, I leveraged both EBM and Laser for different products based on the condition set I outlined above. In some cases, laser was advantageous, and in others, EBM was the better choice. Being technology agnostic empowers one to focus on patient outcomes, first and foremost, and production efficiency; I firmly believe both technologies have a place in the industry and each will make a tremendous impact as the technologies becomes more adopted and accessible.
All that being said, from the perspective of an OEM, what does the industry need most urgently? In short, I believe we are in desperate need of additional EBM capacity specifically for Medical, as there are very few suppliers with the current EBM platform technology. Moreover, a new supplier should have experience working with the platform, designing components using AM tools, AM-produced product testing, and downstream manufacturing considerations. Such suppliers should also have a good grasp of the different software tools available, including those for lattice structures and build preparation to help their clients make informed decisions, particularly with regards to testing for FDA submissions. Also, nice to have would be additional capabilities and/or an extended network to help clients bring new products to market, whether with secondary machine shops or regulatory consultants.
In addition to EBM-specific suppliers, there is a more general need for more experienced AM service bureaus with Orthopaedics knowledge. But look who I’m telling…
Bottom line? There is no doubt that AM is a big part of the future of the Orthopaedics industry. Improved patient outcomes, greater efficiency, and improved quality – the impossible trinity realized! Getting the technology pathway right for each of your AM designed and produced products will go a long way in helping you – and your customers – to realize these wins.
Reference 1 – Newer laser systems currently under development may allow for multi-layer builds similar to current EBM capabilities, but at present, the EBM system is the only option.
For more information, you can contact Brian on LinkedIn or below