To many of you having a spinal fusion, you may not be aware of the enormous biomedical engineering research and design effort that goes into the every implant used. Titanium and its alloys are metals which have a long track record of being biocompatible. We use titanium throughout the skeleton for trauma, dentists use it for implants, and of course we use it for the screws and rods for fusions.
For reasons that may be historic, however, for many years we’ve been using PEEK – a form of plastic – in the interbody space where the disc is removed. By itself it does not cause any artefact when X-rayed, and has some other theoretical advantages too. Some doubt has been cast though on the effectiveness of PEEK and whether or not it may inhibit bone formation – the exact opposite of what we want to create a fusion.
I’ve been very fortunate this year to have been involved with a Dutch/German company called EIT who asked me to help design their interbody cages for PLIF. The cages are made using a 3D printing technique called Selective Laser Melting and then treated with a process that roughens the surface making it more attractive for osteoblasts, and that’s what you want to make a fusion. You can see an explanatory video here.
The new cages are safe to use, don’t require any changes to surgical technique, and have minimal impact on post operative imaging, which is often a concern with solid metal implants. As you can see below, even with PEEK cages below, there is significant “noise” from the tantalum markers inserted into the PEEK. The EIT titanium cage inserted at the level above though has none of this noise and it’s relatively east to see the fusion progressing.
This is a cage that bone grows towards, and through, and I believe represents the next step in fusion technology.I’m now using EIT titanium cages for PLIF, TLIF and ACDF procedures, and have been very satisfied with the results.
Declaration: I do not receive any royalties from EIT but obviously have a research and development agreement with them.