3D printing customisable and antibacterial hip joints

Materials World magazine
29 Aug 2019

A 3D-printed zirconia ceramic hip developed by Chinese researchers has antibacterial properties, for improved joint health. Idha Valeur reports.

Researchers have made a ceramic hip joint that can be customised using 3D printing. The joint is created by combining the ceramic 3D printing technique with antibacterial nano-modifications.

Current titanium hip joints are less durable than ceramic options, with a shorter lifetime of less than 20 years. Nanchang University Institute of Translational Medicine Professor, Xiaolei Wang, told Materials World, that due to the metal’s limited wear-resistance, the long-term use of implants based on titanium will result in metal grinding particles appearing, which would cause inflammation around the surrounding tissue.

‘Compared with metal materials, bioceramic material is a promising alternative implant, which can significantly reduce the wear rate of implants. In this research, the ceramic 3D printing technology combined with antibacterial nano-modification can quickly help customise the ideal implant material with precise structure and effective antibacterial properties,’ he said. ‘At the same time, the method of optimising reaction conditions and selecting the area reverse compensation is mainly used to solve two technical problems of fragile and irregular shrinkage. This technology has been successfully applied to rabbits.’

As titanium implants are unable to be customised in advance, several are often prepared for a surgeon to choose from during surgery, leading to waste. ‘More importantly, these non-customised prostheses are still difficult to accurately match the patient’s hip structure. The proposed ceramic 3D printing technology can quickly customise the ideal implant material with a precise structure,’ Wang said.

No room for bacteria

For over a decade, the researchers have been investigating antibacterial properties, and in this test they used zinc oxide (ZnO). ‘ZnO nano-materials were decorated on the ceramic surface, which could destroy the membrane of pathogenic bacteria effectively,’ Wang explained.

The research paper, 3D printed zirconia ceramic hip joint with precise structure and broad-spectrum antibacterial properties, stated that ‘A universal testing machine was used to measure the tensile, bending and compression experiments of ceramic samples. It could be found that the proposed ZnO modification had no significant effect on the mechanical properties of ZrO2 [zirconium dioxide] ceramics.

According to the plate counting results, ceramics modified with ZnO exhibited significantly higher antibacterial efficiency than pure ZrO2 ceramics, the ZrO2-ZnO ceramics had a significant killing effect [of] eight hours. The removed implants and the tissue surrounding the implant were subjected to Hematoxylin and eosin staining. For ZrO2-ZnO ceramics, inflammation was slight, while for pure ZrO2 ceramics, the inflammatory response could be seen that the antibacterial rate of the ZrO2-ZnO ceramics was significantly better than that of the pure ZrO2 ceramics group.’

According to Wang, bespoke antibacterial implants created with their method will be an important trend for the future. At the moment, ceramic joints are more durable than metal ones. However, ‘sintering induced complex structural shrinkage seriously hinders the development of commercial 3D printed ceramic hip joint,’ Wang said.

‘The biggest contribution of the present study is the partition and reverse compensation method, by which the final structure of each customised joint could be predicted accurately. However, a series of China Food and Drug Administration evaluations should be conducted before the commercial use of these delicate and durable implants,’ he added.

The research paper stated that brittleness must be addressed before large-scale adaption is possible. Further research into this is needed.