3D Printing in Medicine – A Transformative Technology

Despite its reputation as an inherently conservative discipline, medicine has always advanced through embracing transformative and disruptive technologies. Specific medical inventions include the humble stethoscope – now very different from the original invention of René Laennec – or the development of the central venous catheter by Werner Forssmann.

In many cases patient care has improved by taking a commonplace or ubiquitous technology and bending it to medical purposes. Something as simple as reliable mail, the telephone, computers and email have now radically transformed medical care.

One of the most eye-catching is 3D printing1 which, put simply, builds objects by placing layers of material on top of each other with precise, computer-controlled mechanisms and novel materials. These enable complex designs to be built reliably, automatically, without constant supervision, and which behave in ways that we would never have thought possible. So what does this mean for medicine?

Surgical planning

In many ways surgery is the ultimate form of personalised medicine – every patient is different and the surgical plan is modified based on what we find when operate. Pre-operative CTs and MRIs have reduced much of that uncertainty.

Using 3D reconstruction software we can make software models which can be viewed and manipulated using virtual reality or even holograms. At Austin Health, we have created virtual reality models to guide robotic surgery,2 making it safer.

We can now design replacement body parts, such as jaws, hips, knees, and spinal implants, which are custom-made to guide surgery and fit individual patients perfectly.

We have also 3D printed liver, 3 kidney, heart and aortic models so that our surgeons can plan surgery to safely remove tumours whilst minimising damage to healthy tissue, prepare for complex back, hip, cardiac or vascular operations. These can also be used to train other surgeons whilst reducing the time needed to learn a procedure. 4,5

Implant manufacture

We can now design replacement body parts, such as jaws, hips, knees, and spinal implants, which are custom-made to guide surgery and fit individual patients perfectly. Instead of cutting bones to fit a standard hip replacement, a 3d-printed cutting guide can tell the surgeon exactly where to cut, at what angle, and how far. Drill and moulding guides can also be made to ensure that screws and plates are placed accurately before inserting a custom-made 3d-printed implant.

This combination of bio-mechanical engineering and rapid prototyping allowed our partners at The University of Melbourne Department of Engineering to design, test, and build a world-first custom-made temporomandibular joint (jaw) replacement.6 The University of Melbourne’s Department of Surgery together Melbourne-based company Anatomics and CSIRO’s Lab 22 has also led the world in creating a titanium 3D-printed heel. 7

Just-in-time production means that it may someday be possible to scan and plan a patient’s surgery, resect a tumour using locally 3D-printed cutting guides, and then even 3D-print a replacement part (such as a plate or scaffold for a skull defect) in the next room to be ready by the end of the operation. If on-site 3D-printing and distributed production becomes as common as desktop printers, we will no longer need large factories, warehouses, or transport logistics – a concept that could radically change the economics of our society.

Materials innovation

“Additive manufacturing” technologies such as 3D-printing create objects from raw materials instead of carving or milling it from a block. This is more efficient and produces less environmental waste.

In the future, your doctor might send a prescription to a 3D printer, creating a single “poly-pill” which contains all of your scheduled medication

Standard desktop 3D-printers use thermoplastic polymers (such as ABS, PLA) as a base material, but almost any combination of adherent materials can be used. These can be infused with drugs, nanoparticles, or even microelectronics. A whole field of engineering called “soft robotics” exists where objects are made of materials that change shape with light, electricity, water, or heat.

Together with a binding agent, drugs can be printed to create multi-layer pills which dissolve in a timed and controlled manner. In the future, your doctor might send a prescription to a 3D printer, creating a single “poly-pill” which contains all of your scheduled medication. 8

The 3D printing of biologically-compatible materials and living cells is also now a reality. “Tissue engineering” involves guiding a cell culture to develop into functioning tissues or organs.

A 3D-printed dissolvable scaffold can be bathed in a cell culture or infused with stem cells. Controlled printing of chemicals which trigger cell development at key points can guide cell growth into a target shape or structure.

Alternatively, live cells can be printed or placed in a specific arrangement to create an “organoid” which approximates the functional unit of a living organ. This may help us create replacement organs in the future, though printing a fully-functional kidney might not be possible.

Medical Devices, Engineering, and Skills Development

In vascular surgery, we use stents packaged into small catheters and deployed via complex delivery systems. These amazing feats of engineering require hours and hours of design, redesign, bench-testing, stress-testing, fatigue testing and often going back to the drawing board.

More importantly this skill-set and collaborative culture between doctors with problems and engineers with solutions is the basis for the next generation of skilled bio-medical engineers that we are training at the University of Melbourne and Austin Health.

3D printing speeds the design of device prototypes, modelling the human body for lab testing, and creating educational and training models for doctors to learn how to use them. Numerous innovative and exciting medical device projects are already underway at Austin Health using 3D printing.

More importantly this skill-set and collaborative culture between doctors with problems and engineers with solutions is the basis for the next generation of skilled bio-medical engineers that we are training at the University of Melbourne and Austin Health.

The Future

There are significant challenges to overcome. Reliable industrial-grade printers are available but they are expensive and the range of bio-compatible materials needs development.

Regulators need to ensure that medical designs and 3D printers are used safely. This signals a paradigm shift in the responsibility for products that do not perform to specification, or what the specifications should be in the first place. Ethical issues arise in whether patients, doctors or specialised “bio-medical engineers” should be allowed to design and make medical parts.

Alexander Bell could not have imagined the impact of the telephone on our society. We are still exploring how 3D printing, materials innovation and distributed manufacturing will change ours. I am proud to be part of a team that leads this work.

References

  1. Coles-Black J, Chao I, Chuen J. Three-dimensional printing in medicine. Med J Aust. 2017 Aug 7;207(3):102–3.
  2. Manning TG, Christidis D, Coles-Black J, McGrath S, O’Brien J, Chuen J, et al. “Plug and Play”: a novel technique utilising existing technology to get the most out of the robot. J Robot Surg. 2017 Jan 2;:1–4.
  3. Witowski JS, Pędziwiatr M, Major P, Budzyński A. Cost-effective, personalized, 3D-printed liver model for preoperative planning before laparoscopic liver hemihepatectomy for colorectal cancer metastases. Int J Comput Assist Radiol Surg. 2017 Jan 31.
  4. Young J, Coles-Black J, Chao I, Barrington MJ. Steps on how a phantom can be 3D printed and embedded within a medium suitable for training of ultrasound-guided procedures. Journal of 3D Printing in Medicine. 2017 Jul;1(3):149–54.
  5. Chao I, Young J, Coles-Black J, Chuen J, Weinberg L, Rachbuch C. The application of three-dimensional printing technology in anaesthesia: a systematic review. Anaesthesia. 2017 May;72(5):641–50.
  6. Ackland DC, Robinson D, Redhead M, Lee PVS, Moskaljuk A, Dimitroulis G. A personalized 3D-printed prosthetic joint replacement for the human temporomandibular joint: From implant design to implantation. J Mech Behav Biomed Mater. 2017 May;69:404–11.
  7. Barnes JE. Manufacturing a human heel in titanium via 3D printing. Med J Aust. 2015 Feb 16;202(3):118.
  8. Prasad LK, Smyth H. 3D Printing technologies for drug delivery: a review. Drug Dev Ind Pharm. Taylor & Francis; 2016;42(7):1019–31.