¹ PhD Student at CREB UPC Biomaterials, Biomechanics and Tissue Engineering Research Group, Eduard Maristany 16, 08930 Sant Adrià del Besòs, Spain.

3D printing of bone grafts. The key of correct and quick bone healing

3D printing is a trendy topic today, both as a hobby at home and as cutting-edge technology in the industry.  It has become more and more popular to use 3D printers to make personal objects, for example, decorative and creative pieces, name badges or gifts to friends. At the same time as being a fun and creative tool, it also serves as an innovative high technology method for fabricating complicated pieces in the industry, and especially in medicine. Health is one of the most popular topics in today’s society and is pushing engineers and scientists to find faster and better solutions for curing our bodies. One of these new solutions is to print synthetic bone.

Bone is a skeletal tissue that protects our organs and give stability to our muscles. Therefore, it is important that it stays intact and healthy. It is made out of two phases, a ceramic phase known as hydroxyapatite and a polymeric phase known as collagen. One of the most amazing properties of bone is that it is capable to self-heal small defects. However, if the damage is too big it has difficulty in regenerating it on its own and needs some additional assistance. We can help bone healing in big fractures by adding a support material, known as bone graft or scaffold, inside the damaged zone. For correct and quick bone healing it is important that this bone graft fits perfectly in the cavity of the missing part of the bone, and has a similar composition to the bone.

3D printing allows for manufacturing bone grafts having the same shape as the missing bone. This is possible as the design of each 3D-printed bone graft is based on the medical images taken directly from the broken bone in the patient. The composition of each bone graft can be changed by using different materials when 3D printing the piece. This means that not only the geometry and the material composition in the bone graft can be controlled, but also the mechanical properties can be changed to fulfil the requirements necessary to stabilize the broken bone.

CREB researchers have made a critical assessment of the recent progress made in the application of 3D printing technologies for bone regeneration, focusing especially on the design of personalized bone grafts. They highlight the possibility to incorporate pharmaceutics into the bone grafts and the analyze the advances in the translation of the 3D printing technology to the biomedical industry and the clinics. The future prospects for this technology are encouraging.

Upcoming advances in commercial 3D-printed bone grafts are expected following recent research advances, aiming at mimicking better and better the natural bone at different levels. For example, polymer-ceramic composites replicating the collagen-hydroxyapatite structure found in the natural bone may overcome the inherent brittleness of purely ceramic bone grafts, which prevents their use in load-bearing applications. Another field of improvement is related to biological performance. Although most current 3D-printed ceramic grafts present excellent biocompatibility, they are still far from the performance of natural bone.

Example of a virtual surgical planning (VSP), including the different steps of a mandible reconstruction and fabrication of the devices required for transferring the VSP into the surgery:

a) Segmented bone defect with the surgical inputs defined (i.e., surgical approach, immobilization system position, fixation screws orientation and osteotomy planes).

b) Design of the cutting and drilling guides.

c) Design of the personalized bone graft.

d) Manufactured cutting and drilling guides fitted into the pre-osteotomized bone defect.

e) Bone defect after osteotomy stabilized with a patient-specific osteosynthesis system and grafted with a MimetikOss 3D personalized 3D-printed ceramic scaffold.

References:

Raymond, Y., Johansson, L., Thorel, E. et al. Translation of three-dimensional printing of ceramics in bone tissue engineering and drug delivery. MRS Bulletin 47, 59–69 (2022). https://doi.org/10.1557/s43577-021-00259-1. ISSN: 0883-7694 Impact Factor: 6.578. Q1 77/334 Materials Science, Multidisciplinary.

Acknowledgement:

This work was supported by the Spanish Ministry of Science, Innovation and Universities through the project PID2019-103892RB-I00/AEI/https://doi.org/10.13039/50110 0011033 and the Generalitat de Catalunya under Grants Nos. 2017SGR-1165 and BASE3D 001-P-001646, co-funded by European Regional Development Funds. Y.R. acknowledges the Spanish Government for the PhD Grant No. DI-15-08184. L.J. acknowledges the Generalitat de Catalunya for the PhD Grant No. 2020DI44. M.P.G. acknowledges the Generalitat de Catalunya for the ICREA Academia Award.