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FORMATION OF ANISOTROPIC STRUCTURE OF POROUS VERTEBRAL IMPLANTS BY PRESSING SPONGY TITANIUM POWDER THROUGH THE ELASTIC PUNCH FACING

  • : Vadim Savich1, Alexandra Shelukhina, Gennady Sheko, Alexander Taraykovich, Sergey Bedenko
  • : 1Powder Metallurgy Institute
  • : PDF Download
  • : 2014

Abstract

A structure of porous implants of cervical and thoracic vertebrae of CVPI system (Cervial Vertebrae Porous Implant) and ThVPI (Thoracic Vertebrae Porous Implant) has been created in Belarus. Their manufacturing process includes using of spongy titanium powder of TPP grade which has been used for over 15 years in the production of porous inserts of hip joint endoprostheses of SLPS system and is approved for use in clinical practice by the Ministry of Health. The structural peculiarity of the implants of CVPI and ThVPI systems is the anisotropy of their pore structure: the porosity of the implants is maximal at supporting surfaces and minimal at lateral surfaces. Such structure provides initial stable fixation, fast osseointegration of the implant, and minimal adjacent soft tissue injury. A technology for the implants’ production has been developed. Titanium powder is poured into a metal matrix; elastic gaskets are placed between the punch and the charge; bilateral pressing occurs at a pressure of 8-20 MPa; the compact is sintered in vacuum at 1190-1230 oC during 1.5-2.0 hours and calibrated by height and lateral surface with simultaneous formation of chamfer on the borderline between side and end surfaces. The presence of elastic gaskets between the punches and the pressed charge allows to distribute the pressure by the surface of sponge powder particles, to avoid their crushing in the surface layer and thereby the reduction of pore sizes and porosity in it in comparison with the internal volume of the product. At the same time, the contact of the pressed powder particles at the lateral surface with the metal matrix allows the latter effect and thereby the anisotropy of properties (porosity, pore sizes) at end and lateral surfaces and inside the product.
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