3D printing has made significant gains as the technology has improved, particularly in the medical field, where printing body parts such as legs and arms has become more commonplace.
Now, the world’s first 3D-printed sternum has now been transplanted into a British patient in a collaboration between CSIRO and medical implant company Anatomics, which is involved in facial implants and spinal applications.
The 61-year-old patient, Edward Evans, previously had his sternum removed due to a rare infection, with the operation carried out at Heartlands Hospital in Birmingham, the UK.
His titanium prosthesis, combined with a synthetic polymer to replace bone, cartilage and tissue, was designed by Anatomics and printed at CSIRO’s Lab 22 facility in Melbourne. It follows on from a previous CSIRO and Anatomics collaboration in 2015 when a Spanish cancer patient received a 3D-printed titanium only sternum and rib implant.
CSIRO printed Evans’ sternum on an Arcam 3D printer, which prints metal parts at reasonably high rates of productivity in a range of materials.
It has previously been used to print a titanium heel implant for a Victorian patient with cancer of the heel bone, who was facing amputation of the leg below the knee.
“This printer uses titanium powder, and we rake a layer of powder on a table. This process operates in a vacuum environment, so it’s a very clean weld and it melts that first layer of powder,” said Andrew Fraser, from CSIRO’s high performance metals team.
“It’s a hot process, so we keep everything at 750 degrees. We use an electron beam to preheat the canvas 700 degrees. Then we come in and use that beam. We do this in 50 micron layers and we just build it up, in this case, thousands of times to build the whole implant.”
Using electron beams instead of lasers can provide a greater power capacity, which means internal temperatures in the chamber can reach about 700 C for titanium.
“This gives a fine microstructure, high ductility and good fatigue characteristics. It also mitigates residual mechanical stresses, enabling you to build large parts without any subsequent warping or dimensional change,” Magnus René, president and CEO of Arcam AB, previously said in an interview with engineering.com.
The sternum had several different features. For example, strong arms required the correct geometry. There were also 'tulips' that attached to the ribs in the implant.
“These needed to have a little bit of support to make sure they came out correctly as well,” Fraser said.
“We were trying to minimise the support on the part overall, especially on the tulip where it has a gripper surface to grip on to the ribs and try to minimise any roughness on that grip from the support.”
Developing both hard and soft parts of the sternum was a challenge, as well as maintaining flexibility in the implant’s polymer so the surgeon could guide tissue around it.
The prosthesis took about 15 hours to print.
“These parts were printed fairly easily – we printed them vertically. On the whole, it’s not a big cross-section of area that we were melting,” Fraser said.
“There were some challenges to printing it horizontally that take a lot more support. If they have the time to print it vertically then that’s a lot easier.”
In an era where printing tissue with a 3D printer has now become possible, other applications for the technology are also increasing, such as in aerospace.
In 2015, Monash University’s Centre for additive manufacturing led a project in collaboration with CSIRO’s Lab 22 researchers and Deakin University for the world’s first 3D-printed jet engine using different additive manufacturing technologies.
Meanwhile, across the other side of the world in the United Arab Emirates, plans are being made for a 3D-printed skyscraper by a Dubai-based company.
As the industry advances and machines are developed that have more powerful beams and the potential to be more precise, print finer details and run faster, the future of 3D printing seems limitless, particularly in the medical field.
“A patient in Australia can opt to get [a 3D-printed hip] implant, in conjunction with their surgeon. That sort of area that’s being developed is ongoing,” he said.
“What we’re working on with Anatomics is patient-specific and trying applications. That’s a real new area for this work.”
[Nominations are now open for the Engineers Australia David Dewhurst Award, Women in Biomedical Engineering Scholarship. Find out more.]