Internal structure of a human bone.

Internal structure of a human bone.

The process of bone formation was discovered back in the 1960s, which led to almost immediate improvements in diagnostic techniques and eventually led to the development of synthetic calcium-based bone repair products. These replacements, called bone grafts, are often made from transplanted bone materials from the patient, cadavers or even some animals. Bone grafts have also been developed using dentin extracted from human teeth that have been ground down into a powder and formed into implants. These days it is far more common for doctors to use a material that will eventually break down in the body and be replaced by the newly grown bone tissue, although metal implants are occasionally required with serious breakage.

For years, bone grafts have been a common method of helping patients with broken or damaged bones to properly heal. Because bone tissue can quickly heal itself, an implant, or scaffold, is used to surgically hold all of the damaged bone fragments together and act as a bridge of sorts that will ensure that they heal correctly. Recently doctors have started 3D printing these implants in order to ensure that the scaffold is sized and fit exactly to the patient’s specific needs. However doctors are limited in the materials that they can use to 3D print bone grafts due to the need for the implants to be strong enough to offer structural support.

A micro-computed tomography image of the 3D printed bone scaffold.

A micro-computed tomography image of the 3D printed bone scaffold. [Image: NTU]

But a group of researchers at Nottingham Trent University are currently studying ways to improve the strength and durability of these 3D printed bone implants in order to promote more successful bone repairs. Their new research has begun to show a lot of promise and it looks like their discoveries could have major implications for patients who have suffered severe bone damage caused by an accident or bone tissue loss due to cancer or other degenerative illnesses. The researchers discovered that by growing unique crystal structures at sub-zero temperatures within the 3D printed scaffolding, not only is the 3D printing time reduced, but the implants are significantly stronger and more resistant to damage.

Nottingham Trent University researcher Manolis Papastavrou with a 3D printed bone scaffold.

Nottingham Trent University researcher Manolis Papastavrou with a 3D printed bone scaffold. [Photo: NTU]

“This research demonstrates how 3D printing in combination with freezing can reduce significantly the fabrication time and cost of such medical devices. The secret behind the toughness of many biological materials is the way their components are arranged from the molecular all the way up to a macro level. Using this design strategy could help engineer bone scaffolds, whose porosity does not compromise their strength. In the long term, this research could contribute in replacing the use of metal in orthopaedic implants with materials that can be broken down by the body,” explained PhD candidate and researcher Manolis Papastavrou.

3dp_boneimplants_ntu_logoThe exact materials used to create 3D printed bone grafts vary from manufacturer to manufacturer, however they all contain many of the same materials found in natural bone. They typically are made from ceramics with high levels of calcium phosphates, but also can be made using bioglass or calcium sulphate. All of these materials are biologically active and will eventually be dissolved or absorbed into the patient’s body. While the materials would naturally dissolve as new bone tissue grew, if the scaffold was too thick or dense it could prevent the bone from healing correctly.

Until this new breakthrough, due to the need for the implants to be porous enough to encourage new bone growth, the strength of the scaffolding was an ongoing issue. The new 3D printed bone microstructures combined with the freezing process developed by Papastavrou and the rest of the researchers at Nottingham Trent’s Design for Health and Wellbeing Research Group was recently presented at a conference titled Printing for the Future. The day long presentation event took place on January 19th 2016 at the Institute of Physics, London. Discuss your thoughts on these new materials in the 3D Printed Implants With Crystals forum over at 3DPB.com.

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