3D printing for personalised prosthetics

Dr Kerwin Shannon - Sydney Head and Neck Cancer Institute, Sydney, Australia

Technology, new technology in the care of oral cancer, my particular brief was on imaging and 3D printing and its role in reconstruction of large oral cavity defects.

How are you using 3D printing in oral cavity repair?

The large defects are usually repaired now with free flaps, composite flaps using bone and soft tissue and in the past creating new mandibles or new maxillae was a bit of an eyeballing job, trying to create an arched structure from a straight piece of bone. So it requires cutting the bone and putting it into place and making it fit the shape. You’re also trying to do the reconstruction so that people get good cosmetic and functional outcomes. What has been found is that if you plan these things virtually before putting the flaps in place you can actually get better alignment, better joining of the bone and better functioning. The way you do it, you send modern CT and other imaging data to a modelling company, they put all that data into software and create virtual models. You also send images of the limbs or the bones you’re going to use for the reconstruction and you actually do the cuts on a video screen. What you’re able to do then is create polymer models of the skeleton that you’re trying to reconstruct, you create the guides that you’re going to use to help cut the bone. So whereas before you’d spend a lot of time in the operating theatre making little tiny adjustments, trying to make things fit into the right slot, now you put the guides on already pre-planned, do the cut, slot them into place and all the hard work is done.

What forms of 3D printing do you deal with?

The printing comes in a number of places. Firstly, the polymer models that are made can be manufactured with 3D printing. The particular company we use, I don’t know how they manufacture them but certainly 3D printing is an easy way to go and it’s cheap. One of the exciting developments that has happened recently though, there was actually an article in the popular press in Sydney a couple of weeks ago, a young man had a titanium implant printed for his particular bone. So they’re actually using the titanium as the printing element and there is an enormous scope for prostheses to be individualised. Normally you would have a standard set of prostheses that you would pick one that was an appropriate side and then you would make adjustments on the patient to make the prosthesis fit in. Now if you can create a model of the deficit you can actually print up a prosthesis which is the right size for that individual patient and it’s very exciting technology.

There’s also scope in the future with tissue engineering, potentially the ability to culture cells and print those onto scaffolds of some sort, printing up the scaffolds for the cell culturing. Or using the cell cultures in gels as the tissue that is being printed. So that’s something to look out for in the future.

So this is with titanium rather than plastic?

For this particular one that was in the press, the prostheses that was the head of the mandible was titanium. They used a polymer as the glenoid fossa, the space that the joint was fitting in to. If you don’t have a barrier in that bone metal prostheses can actually force their way through the bone so there’s a polymer placed in the way. So both the joint space and the joint prosthesis were printed up using two different materials.

What is your take home message for doctors interested in 3D printing?

Watch this space. One of the main reasons this is becoming so exciting is basically because of computing power. One of the things I did in my presentation was to pull an external hard drive out of my pocket which had 635 patients’ images on it and from this I can import that into my own laptop, I can create 3D models, I can use that for patient education, I can use it for resident education but that data can also be uploaded and manipulated in so many ways. I think that in the future the reconstruction will be individualised, creating the materials for the particular defects rather than the manufacturers giving us a tray of options that might fit a particular patient, having to bend a straight bar into a curve so that it fits on a particular patient, they can actually print up the shape of the strut that needs to be put there for that individual’s bone and it can match every curve and bump in the bone.