Scientists of the Moscow Aviation Institute are developing a technology for producing a nanostructured material based on titanium

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Scientists of the Moscow Aviation Institute are developing a technology for producing nanostructured titanium-based material with controlled porosity for bio- and mechanically compatible osseointegrating medical implants.

“The peculiarities of the technology are that in order to obtain a porous material at the first stage, we use initial fibers of about 20 microns in diameter, obtained by high-speed solidification of the melt,” says the project manager, Doctor of Technical Sciences, Professor of MAI Mikhail Kollerov. “We call it the hanging drop method. Its essence is that molten titanium does not come into contact with crucibles, which can dissolve and contaminate the material. A rod of commercially pure titanium is melted by a heat source – an electron beam gun. And the drop, falling on the rapidly rotating cooled copper disc-crystallizer, solidifies. Depending on the shape of the mold disc, its rotation speed and the power of the gun, we can obtain different shapes and sizes of fibers. The latter range from 5 to 50 microns.

At the second stage, titanium fibers are pressed based on its further use – in the form of a sheet, a rod or a specific implant, at the third stage – diffusion welding or sintering under a certain load.

“We have tested the porous material for tensile, bending, shear. Since the project deals with osseointegration material, the following requirements are imposed on it, first of all, volumetric, completely through porosity – from 50% to 80%. The pores themselves should have an average size, ranging from 50 microns to 500 microns, so that osteoblast can grow through them when replacing bone tissue. Our calculations showed that in order to achieve the required strength, the average pore size range should be in the order of 200-300 microns, ”the project manager explained.

The fourth stage is the thermohydrogen treatment of the porous material, which consists in introducing hydrogen into titanium by the thermal diffusion method (when heated in a hydrogen gas atmosphere) and removing it during subsequent vacuum annealing. During this treatment, titanium undergoes complete phase recrystallization, as a result of which its structure is refined to nanoplates, and common structural components are formed at the contact points of individual fibers, which provide a significant increase in the strength of the porous material.

“After thermal hydrogen treatment, we managed to increase the strength characteristics of the porous material by 1.5–2 times,” said Mikhail Kollerov.

The project participants have already manufactured and tested experimental samples of sheet and bar nanostructured osseointegrating porous material.

 Appearance of samples of osseointegrating porous material made of titanium

Preclinical studies of implants, although not foreseen by the project, were still carried out. Together with the Hematological Research Center under the leadership of the head of the department of orthopedics, candidate of medical sciences Vasily Mamonov, 20 rabbits were operated on, which were implanted into the place of the bone defect. “The results are very good – complete sprouting of bone tissue within three months,” said the scientist. –

Our porous material is at least not worse than the existing ones, and in some respects it surpasses them. “

The industrial partner – CJSC “Implant MT” – specializes in the production of hip and knee endoprostheses and plans to produce osseointegrating coatings from porous titanium created by the project participants, which will ensure reliable fixation of implants in the bone and reduce the risk of postoperative complications.

Models of vertebral body prostheses and a cup of a hip joint endoprosthesis with an osseointegrating coating made of porous titanium fibers

At present, the industrial partner has manufactured models of endoprostheses for vertebral bodies and acetabular components of hip endoprostheses with an osseointegrating coating made of porous titanium. Technical tests of the models showed the high strength of the porous material and the adhesive strength of the coati

ng. Source: http://www.strf.ru