What if surgeons could replace damaged bone with a solution tailor-made to each patient?
That's the question researchers at the University of Waterloo are seeking to answer as they develop a material that mimics the behaviour of human bone and is capable of being 3D printed with a high degree of accuracy.
Identifying a solution
Lead researcher Dr. Thomas Willett, from the Department of Systems Design Engineering, was influenced by his experiences working with orthopaedic surgeons at Mount Sinai Hospital in Toronto.
"I learned that the methods being used, though successful, were extremely complicated and required a lot of skill," Willett said. "I thought we could do something with engineering, using 3D printing to produce a bone graft."
Many surgical procedures require bones to be repaired and replaced. This is typically done using metal implants and donated tissue that acts as a framework for new bone growth. Doctors try to match available donated bones with the patient, but it can be hard to find an exact fit.
A material that is suitable for grafting but also 3D printable would enable surgeons to precisely match the geometry of the bone being replaced. This would make the process much easier and safer, with less likelihood of rejection or infection. "3D printing would also allow us to add engineered features that can hold the graft in place," Willett said. "This would remove the need for the metal screws and plates that surgeons would normally use.
"We could have a material that you can fully customize to a patient, and that will have a big impact on the success of bone grafts and surgical outcomes."
Elizabeth Diederichs (PhD in progress)
Crafting a new material
Backed by funding from the Canadian Institutes of Health Research, Willett and his collaborator Dr. Maud Gorbet, director of the Biomedical Engineering program, set out to make this material a reality.
The research group also benefited from the contributions of young researchers including Dr. Dibakar Mondal, Dr. Sanaz Saadatmand Hashemi and Elizabeth Diederichs (PhD in progress), who continues to work with Willett.
At the core of their work is a new nanocomposite material. It combines a triglyceride that is similar to fat with a nanoscale particle called hydroxyapatite.
"The hydroxyapatite particles play a few roles," Willett explained. "They provide mechanical reinforcement, making the material stiffer and stronger. They also create a favourable surface for the material to combine with bone cells."
As the body repairs itself, the unique properties of this material allow new bone tissue to interact with and gradually replace the graft. A 2024 study published in the Journal of Biomedical Materials Research confirmed that materials containing nanoscale hydroxyapatite particles are a viable potential alternative for grafting.
Optimizing for the future
The researchers are now focused on refining their material to function both in the human body and through the 3D-printing process. "The challenge now is optimization," Diederichs explained. "It's a balancing act between all the different qualities we need."
Diederichs's work focuses on getting the material to be durable enough to withstand the pressures of the human body, while also being capable of slowly degrading to allow for new bone growth.
The team wants the material to be compatible with the highest accuracy 3D printers available, ensuring that grafts are precisely fitted to each patient.
"We can take CT scans and use computer-aided design to develop a model for the piece of bone that needs to be printed," Willett said. "We could use this process for any bone that has lost a large piece or has complex geometry." Printed bone grafts could also have applications for pets, reducing the need for amputations that impact quality of life.
This painstaking work has the potential to transform skeletal repair and reconstructive surgery by dramatically improving patient outcomes.
"I think it's very exciting," Diederichs said. "We could have a material that you can fully customize to a patient, and that will have a big impact on the success of bone grafts and surgical outcomes."
