Custom 3D-printed implants could transform how complex bone injuries are treated, shifting the focus from replacement to regeneration.
For decades, orthopaedic implants have followed a simple rule: replace damaged bone with something stronger. Titanium has been the default – reliable, fatigue-resistant and capable of bearing load in demanding environments. But it was never designed to behave like bone itself.
Professor Hala Zreiqat has spent her career challenging that limitation. A biomedical engineer at the University of Sydney and the recent recipient of the Suzanne Cory Medal, Zreiqat is using advanced materials and 3D printing to rethink what an implant is supposed to do.
“I set out to explore whether we can create materials that become part of the body, not just simply sit there to provide structural support,” Zreiqat said. “I built a multidisciplinary team, bringing together biologists, clinicians, material scientists and engineers.
“Since 2006, we have built and developed a new generation of bioactive, 3D-printed ceramic materials designed to actively regenerate bone under load-bearing conditions.”
It’s a shift that could redefine how implants are designed. But turning that idea into reality is far from straightforward. Bone is not a simple material, and replicating it means solving multiple engineering problems at once.
Why bone is so hard to replicate
What makes bone difficult to engineer isn’t any one particular feature, but how many roles it performs at once.
“Nature has already engineered bone into a remarkable material. It’s as strong as cast iron, but it’s lightweight like wood,” Zreiqat said.
Bone is often treated as a structural material, but it behaves more like a hierarchical system, she explained.
Dense outer layers provide strength, while the internal structure distributes load and absorbs energy. Meanwhile, the porous network allows blood vessels, nutrients and cells to move through the material.
“The challenge then becomes creating a synthetic material that is strong enough to carry load, but also porous, because bone is very much alive – it needs all these biological processes to occur in order to build new bone,” she said. “Achieving this balance has been – and still is – extremely difficult.”
Matching that combination of properties is only part of the challenge. Where traditional implants stop at structure, Zreiqat’s team is going a step further by designing materials that can actually interact with the body.
“We design materials with biologically important ions like strontium, zinc and magnesium. So the material is not just passive, like cement filling a hole. It’s designed to play an active role in helping to guide the body’s own regenerative process to build new bone.”
READ: Hala Zreiqat wants to 3D print new bones on demand
Designing the implant
Translating these ideas into real-world use means treating geometry, mechanics and biology as a single design problem.
The process begins with a CT scan, creating a detailed 3D map of the patient’s bone and the defect. From there, the question becomes how that structure will behave once it is back in the body.
“We need computational modelling to understand how that bone carries the load and inform the implant design, [because] we cannot predict where the load will be mostly applied,” Zreiqat said.
Once the external form is set, the real design work moves inside the material. Zreiqat compared this to LEGO: you can assemble the same outer shape in different ways, but its strength ultimately depends on how the internal pieces are arranged and connected.
3D printing allows engineers to control pore size, distribution and connectivity with a level of precision that would be difficult to achieve otherwise. It also makes it possible to reproduce those designs consistently.
“In a sense, we are creating an instruction manual of how a material should be built and how the body’s cells will interact with it,” she said.
Each implant is designed to fit the patient’s anatomy and the specific mechanical demands of the defect, while at the same time influencing biological processes.
The combination of structural support and biological signalling is what allows the implant to act as a scaffold rather than a substitute, gradually being replaced as new bone forms.
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From breakthrough to impact
The potential of these materials is already starting to move beyond the lab.
“Our technologies have been acquired by Allegra Orthopaedics, which is advancing it through to spine fusion devices, and they’re working very closely with the regulatory bodies to bring it closer to clinical applications,” Zreiqat said.
However, even as the technology advances, barriers still remain. Large, load-bearing defects continue to push the limits of what these materials can achieve, particularly in the parts of the body that take the greatest strain.
Getting these materials into real-world use also means overcoming regulatory hurdles. Personalised implants don’t fit neatly into regulatory systems designed around standardised products, she explained.
“The regulatory systems rightly prioritise patient safety, but they often work best for incremental improvement to existing devices, rather than a disruptive innovation. So, bringing these innovations to patients requires not just scientific breakthrough, but also close interaction and collaboration with regulatory bodies and health care systems to keep up with the pace of innovation.”
The progress so far has been recognised at the highest level. Zreiqat was recently awarded the Suzanne Cory Medal by the Australian Academy of Science, acknowledging not just a single breakthrough, but decades of work tackling one of medicine’s most complex engineering problems.
“It’s really a tribute to [our] interdisciplinary collaboration, and a reminder of our responsibility to turn these discoveries and the funding provided from the federal government into real impact for patients.”
This webinar explains the application of digital manufacturing tools such as finite element analysis and 3D printing in engineering design and biomedical prototyping.
