With the right design, titanium implants can be moulded closer to the form and stiffness of human bone. To perfect the design all you need is an algorithm and a 3D printer
This coral-like form is a spinal implant. Created by Californian medical company NuVasive, it is made from titanium and fits precisely between two vertebrae. By mimicking the porousness and stiffness of human bone, it can accelerate bone growth following back surgery.
Spinal surgeons typically use implants made from high-performance plastic, because the material is less rigid than metal, yet also porous. But NuVasive’s research demonstrated that, with the right design, titanium could be moulded closer to the form and stiffness of human bone – with the added benefit of being stronger than plastic. But how to make it as porous while keeping this strength? Put a computer in control of the design.
The process is known as generative design: NuVasive sets constraints – such as the implant’s weight and porousness – into its software, and then asks the algorithm to spit out solutions that fit the brief. Humans have preconceived notions about the way something needs to look, but computers don’t – so it’s easier for them to offer original ideas.
“You describe your problem, and the computer creates a large set of potential solutions,” says Jeff Kowalski, chief technology officer at Autodesk, which designed the Dreamcatcher programme used to create the implant. “In the time it would have taken you to do one design, Dreamcatcher has done all of them.”
Once the most suitable model has been selected by a human designer, NuVasive 3D prints the implant. The computer’s latticed, asymmetric design means it can be made of titanium, a material that is strong and easy to detect in X-rays, yet still lightweight. “We’re able to tell it what load we’re putting on the implant and then the lattice is actually able to grow and shrink in thickness based on those loads, which leaves us with the least amount of material to meet strength requirements,” says NuVasive development engineer Jesse Unger.
Image Credit: Andy Barter