Mechanical strength and bone bonding of a titanium fiber mesh block for intervertebral fusion

Abstract

We developed a titanium fiber mesh block (TFMB) to use as an alternative to autogenous bone grafts for vertebral interbody fusion. In in vitro tests, we measured the surface pore size and conducted weight loading tests of TFMB with porosities of 50% and 60%. For in vivo testing, we grafted TFMB in 11 mongrel dogs for intervertebral fusion and evaluated bone ingrowth into the grafts and the bonding of TFMB with bone. The mean surface pore size was 375 ± 289µm for 50% porosity TFMB and 445 ± 400µm for 60% porosity TFMB. In the in vitro weight loading test, 60% porosity TFMB showed 50%-60% of the elastic modulus of 50% porosity TFMB, and both materials showed a similar yielding load. After the grafting of 60% porosity TFMB, bone ingrowth occurred to a depth of 2.3mm at 3 months and to a depth of 3.6mm at 6 months; while the values were 0.7mm and 1.5mm, respectively, in 50% porosity TFMB. In a push-out test conducted 6 months after grafting, 50% and 60% porosity TFMB showed similar bone bonding strengths. These results suggest that 60% porosity TFMB implant will be suitable to using for spinal interbody fusion.