3D printing (or additive manufacturing, if you are particular about this kind of thing) is affecting all industries and a number of healthcare applications are developing and market research organisations are as usual predicting a market for its health applications to be in hundreds of millions. Astute readers will, of course, ignore projections and focus on the more compelling reasons to be excited. The promise of 3D printing in medicine is being delivered over a continuum of complexity. At the left side of the scale is  use of 3D printing to build personalised body parts where the function depends on the macro structure and on the right is use of 3D printing to make complex organs where the function depends on micro-structure of the body part. (There are ex-vivo 3D printing applications which I discuss here and 3D printing applications in drug delivery are discussed elsewhere.)

The first application, which relies on being able to make simpler body parts for external or internal use is more near term and has shown promise already. The premise is inescapable, all humans are different shape and size, replacing body parts with standard off the peg products is not a perfect solution. It is somewhat more acceptable and possible where you are using standard joints etc but when a condition e.g. cancer or an accident damages a part of your body how do you replace it to fill the exact gap. 3D printing offers to fill this void. A cancer patient recently needed his sternum and ribs replaced and a 3D printing lab was able to make a titanium replacement to fit the destroyed part exactly.

3D Printed to Perfection

This area is ripe with innovation, lots of companies trying to (literally) fill the gap with their products. The idea is even more compelling in cases where you are making things for children who will grow and will need a new part tailored to their needs. I came across Andiamo which was born out of a couple’s frustration with the slow and inconvenient (and ultimately dysfunctional) process of making plaster moulds of kids and making braces and splints which take so long to make that when they arrive, they don’t really fit. They are automating the process of measuring, printing and delivering braces (that fit!) within 48 hours using off the shelf 3D printing technology. This is the perfect example of where combining a bunch of technologies can deliver a result that is life changing. Hats off to Andiamo.

The key in this type of enterprise is that by combining the high precision of measurement (using laser scanning or using 3D CT/MRI data) with high precision additive manufacturing to build things that are exact replicas of a biological part. This opens up applications such as printing diseased parts of the body to understand them better and to use the physical embodiment of them to plan treatment. You may have heard of the MIT engineer Stephen Keating who discovered his brain tumour by accident and then printed it and assisted surgeons in removing it (see video).

[youtube https://www.youtube.com/watch?v=-L-WFukOARU]

The promise is that one day we can print complex microstructure and scaffolding of body organs designed in such a way that they can carry out the biochemical processes of the organ to near human level

3D Printing Can Replicate the Layered Nature of Organs

(obviously then moving to do it better than human organs). Most biologists and healthcare technologists find the idea of organ printing intriguing because replacing damaged organs with functional units is a remarkably effective way of alleviating suffering and preventing deaths. Organ transplantation is one of the most effective medical procedures limited largely only by the shortage of transplantable organs. Apparently, it kills 30 Americans every day.

The main hurdle in making organs is that a functioning organ is not a mass of cells, it is essentially a fully engineered processing plant that allows a process to take place (filter urine in the case of kidney or transport of oxygen in the case of lungs) and just like any processing plant just having the machines is not enough for the process to take place, but having them interconnected in the right way to move the process forward is also critical. These cells all need nutrients, oxygen etc., and it is very hard to build and connect blood vessels in these organs. In nature, this organisation of cells, the construction of blood vessels happen first in the embryo and then the fetus when layers of different types of cells come together and organise to form a functional organ. Therefore, despite scientists being able to culture a wide range of cell types have been frustrated by not being able to make them work as organs.

Anything so fascinating and transformative is bound to generate a lot of interest, and one think ‘lot of interest’ does often is create hype.  It is not unusual to find on the internet claims of inkjet printers churning out functional kidneys etc. which are inaccurate (or false, in common language). No one has actually managed to print a fully functional kidney or liver yet. A lot of this hype followed a TED talk by Dr. Anthony Atala who is a remarkable scientist who has dedicated his life to regenerative medicine but because of the way his talk came across and because of high levels of endorphins in the TED water people got a little bit carried away (more on that another time).

Once you overcome the noise though, you realise that even though artificial solid organs like kidney and livers which people are more excited about (and which we need in large number of), many patients have benefited from from 3D printing and some of them are only alive today thanks to this technology. Here are a few examples:

Trachea (windpipe)
Jaw
Skull
Bones

So the rule of thumb is this: If it is a body part with largely structural role or a scaffolding – Yes
If it is a body part with a biochemical role and needs blood and/or nerve supply – Not Yet

VG: last edited September 2015