NUST MISIS Scientists Develop Unique Implants

NUST MISIS`s young scientists have developed a new method to produce ultra-high molecular weight polyethylene implants intended to replace bone tissue defects in humans and animals.

The new implant imitates bone tissue structure and consists of aporous inner layer and a solid outer layer. In an organism, its spongy structure enables newly formed blood vessels and tissues to grow into the implant. The solid layer is added for strength and bears the bulk of the pressure.

Finely divided 100-mikrometer ultra-high molecular weight polyethylene powder is used in the manufacture of the implants, with high-purity salt introduced to form pores. Special presses reduce the mixture to a solid mass. Next salt is washed out under conditions where water is liquid in temperatures ranging from 100 to 374 degrees Celsius and under pressure of 218+ atmospheres (subcritical water). The next step is to dry the implant and to reinforce it with a solid layer of ultra-high molecular weight polyethylene.

An antibacterial additive is infused into the implant’s upper layers, where it forms a stratum that will protect the organism from inflammation and help to avoid infection. The porous part is seeded with cells taken from the patient’s bone marrow and proteins stimulating their ingrowth into bone tissue.

Implants will be used to replace sections of tubular bone tissue in injuries or cancer cases, including flat bones — pelvic, cranial, shoulder-blade, etc. — exposed to low and medium loads. The technology can also be used in animals.

“Our implants have several important advantages. First, they are made from light but strong material that can sustain low and medium pressures (its total compression strength is up to 80 MPa). Due to their unique structure, our implants are superior to their counterparts from Europe and the US in terms of strength. Second, the material is highly plastic: a surgeon can cut the implant to size, something that can’t be done with titanium implants. Third, the porous structure fills 80% of the implant blank, enabling the implant to be quickly overgrown with tissues and blood vessels. On top of that, the material is rather cheap: a 50 cm3 implant blank without sown cells and proteins costs about 10,000 rubles,” Fedor Senatov of the Center for Composite Materials at NUST MISIS said.

It took four years to develop the new implant-making method and the effort is still in progress. Initial preclinical tests have been successful. Researchers have applied for two Russian patents and are planning to patent the method internationally. There are plans to produce a free pilot batch of implants for veterinary clinics soon.