Tips for using 3D printing in medical applications
In a recent webinar, guest presenter Katie Weimer, Vice President, Medical Devices at 3D Systems Healthcare noted that 3D printing has moved past being an idea and is now a part of the mainstream of healthcare.
Today, more than 10 million 3D printed hearing aids are in circulation. Align Technologies, which manufacturers Invisalign teeth guards, uses 3D printing to print 140 custom units per day. Another popular use is the creation of surgical guides for osteotomy in the knee area; each guide must be custom to fit specific patients knees.
“I think this is a growing application and it will likely spread to other joints such as hip, shoulder, ankle and we will continue to see that grow over the coming years,” said Weimer.
The major 3D printing technologies used in the medical industry are fused deposition modeling, laser sintering and stereolithography.
Fused deposition modeling is popular for low-end, low-cost prosthetics. For the development of medical devices, Weimer noted that the Food and Drug Administration said that they see about 81% of the medical devices made using metal powder bed fusion, and 13% using stereolithography.
As for the materials used, it’s about 50/50 polymer and metal. The alloy Titanium (such as Ti64) dominates the metal materials, with cobalt chrome and Commercial pure Titanium being a small portion of the remaining metals.
Weimer noted that more than 70% of the 3D printed medical devices seeking FDA approval were cleared through the 510(k) section of the FDA regulations. Said Weimer, even 3D printed devices must go through the same approval pathways as non-additively made devices.
There was a significant increase in devices clearing 510(k) regulations during 2011-2012. Many of these were for orthopedic applications.
Said Weimer, “It’s just a mind shift as a designer if you worked outside the medical industry. You are now under a different set of rules [for medical]. In general, the scope of any additively manufactured device follows the circle from regulating receipt of material, design of product, premarket testing, manufacturing, final inspection and all the way through to the shipment of the product. I think it’s important as designers to understand that there are different classifications of medical devices, which may have different design burdens or regulation of design associated with them.
“It’s not just about the printer,” continued Weimer, “but about the entire flow of the digital concept as it comes in through medical imaging data, gets processed, planned, designed and then eventually used in surgery. In our experience, we really had to rethink how we design. Patient geometry, patient anatomy is very organic by nature. As such, patient design can become very complex and I think in the case of personalized surgery, which I think is where 3D printing is going in healthcare, we had to really find different software tools to handle these types of organic geometries.”
A custom hip, for example, has to fit in the surgical field and in the area of exposure. It has to maintain the right strength and the right functionality for a hip prosthesis, but also has to be contoured correctly for a patient’s long-term use.
In some cases, haptic design offers a way to handle these types of geometries.