Titanium with aligned, elongated pores for orthopedic tissue engineering applications.

Porous titanium with elongated and aligned pores, mimicking the anisotropic structure of bone, was created by solid-state expansion of argon trapped in elongated pores between titanium wires. Both elastic moduli and yield strengths are larger in the longitudinal direction (E = 51 GPa, sigma y = 338 MPa) than in the transverse direction (E = 41 GPa, sigma y = 267 MPa). Finite-element analysis of simplified anisotropic structures provides insight into the local micromechanical behavior of these porous materials, evaluating elastic modulus, resistance to plastic deformation, and localized stress concentrations which may be experienced under biological loading. Preliminary in vitro cell culture studies further demonstrate the influence of the elongated porous microstructure on osteoblast colonization behavior. These studies suggest that as an optimized material, titanium with aligned, elongated pores is promising for applications in orthopedic tissue engineering, as it combines high strength, toughness, and biocompatibility of titanium with the reduced stiffness and open porosity suitable for mechanical integration with bone tissue produced by aligned pores. (c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.