In vivo study of stainless steel and Ti-13Nb-13Zr bone plates in a sheep model.

A sheep study was performed to compare the in vivo performance of bone plates of 316L stainless steel and a new titanium alloy, titanium + 13% niobium + 13% zirconium (Ti-13Nb-13Zr), which had been subjected to a diffusion hardening treatment to produce a blue, wear resistant surface. Bone plates and screws of stainless steel and diffusion hardened Ti-13Nb-13Zr were implanted in adult sheep, in one group (with unosteotomized femurs) for 16 weeks, and in the other (with osteotomized femurs) for 8 weeks. At harvest, the diffusion hardened Ti-13Nb-13Zr devices had superior fixation strength, with greater screw torque out strength and fewer loose screws. In the osteotomized animals, the femurs with diffusion hardened Ti-13Nb-13Zr plates had higher torsional strength after removal of the implants; however, the difference was not statistically significant. In the unosteotomized animals, the torsional strength of the femurs was identical for both materials. There was a slightly reduced incidence of infection (bacterial adhesion) for the sheep with diffusion hardened Ti-13Nb-13Zr implants. In a parallel in vitro study, the magnetic resonance imaging compatibility of Ti-13Nb-13Zr was significantly superior to that of stainless steel. This indicates that diffusion hardened Ti-13Nb-13Zr may be an attractive alternative material for osteosynthesis.