MISiS: 3D scaffold printing method for auxetic metamaterial implants

Main article: 3D printing in medicine

2023: Printing material to improve durability of intervertebral implants

Scientists method MISIS University patented 3D printing of a three-dimensional framework from auxetic metamaterials, which can be used for implants prostheses intervertebral cages to medicine and in the future. Zdrav.Expert This was announced on August 31, 2023 by representatives of MISIS.

Russian scientists have printed material that increases the durability of intervertebral implants
Ha photo: Prototype from auxetic

Auxetics are a special class of metamaterials that behave in unusual ways when stretched or squeezed, scientists say. Instead of expanding in all directions, they contract in the transverse direction. For example, the elastic band becomes longer when stretched, but is thinner in width. This is because the material has a negative Poisson ratio. Medical applications of auxetics include prosthetics, orthopedic products, ergonomic devices, performance devices, invitro medical devices for cell interaction, and advanced medical clinical products, especially tissue engineering scaffolds with living cells.

"Auxetic metamaterials, due to their unusual structure, can be optimal for the loads that the human body experiences. Such structures are able to effectively cushion shocks and vibrations, reducing the risk of damage to bones and joints, - said co-author of the patent Ph.D. - med. Fedor Senatov, director of the REC of Biomedical Engineering NUST MISIS. Cell-based auxetics are suitable for use in products such as scaffolds, bone implants, cages and others. Rotating geometry-based auxetics are better for flexible medical devices such as stents, musculoskeletal patches or soft tissue scaffolds. "

As noted in MISIS, as a replacement for the classical porous structures used in bone grafts, cell-based auxetics are the most promising. According to clinical studies, in 12% of cases, spinal cages after implantation migrate, and in 5% they completely collapse under load, since intervertebral discs serve as a shock absorber of mechanical effects, provide a certain angle of bending, twisting and rotation between neighboring vertebrae. The geometry that forms auxetic metamaterials plays an important role in varying the properties of cages, potentially reducing the effect of stress shielding and increasing the life of the product, the university emphasized.

NUST MISIS scientist Vladislav Lvov improved the commercially available interbody cage by introducing the auxetic metamaterial structure into the volume of the product. The cage itself was obtained by 3D printing with titanium alloy powder Ti-6Al-4V.

Prototype from auxetic

"3D printed cages from auxetic metamaterials with structures with an angle of inclination between the ribs less than 90 ̊ show higher static compressive strength and fatigue strength. Therefore, they can become an excellent basis for intervertebral cages, supporting areas of the damaged spine and promoting bone growth in the treatment of degenerative disk disease, "says Vladislav Lvov, Ph.D., engineer of the 1st category of the REC of Biomedical Engineering NUST MISIS.

Parametric solid-state modeling was used to optimize the intervertebral disc prosthesis for auxetic metamaterial. At the first stage, the elementary configuration of the auxetic cell is distinguished. At the second stage, a parametric system with interconnected dimensions is created using a computer program. The system combines the base section of the cell with geometric parameters, making them interconnected, so that when one parameter changes, others change. The computer algorithm then simulates mechanical, thermal and other tests. As a result, the optimal geometry of the auxetic with a set of necessary properties is selected, explained in MISIS.

As of the time of publication of this material, scientists continue to investigate new areas of application and implementation of auxetic metamaterial for specific tasks of spinal surgery in order to ensure comfort, support and safety for people with spinal problems.

"Scientists of the scientific and educational center of biomedical engineering of the University of MISIS, within the framework of the federal program" Priority-2030, "are developing in the field of tissue engineering, biophysics, targeted delivery of drugs and bioprinting, new technologies and materials that increase the effectiveness of therapy, - said the rector of NITU MISIS Alevtina Chernikova. - The strategic project "Biomedical materials and bioengineering" combines the efforts of leading universities, research centers, innovative enterprises of the country. One of the key areas of the Health Engineering consortium is the creation of a line of spinal cages that can return thousands of people to normal life.

As she added, at the production site of CONMET, one of the business partners in the consortium, research was carried out on the development of technology for the formation of intervertebral cages using the 3D printing method. Industrial production medical products are scheduled to be launched in 2025.