Porous nitinol vs. titanium intervertebral fusion implants: Computer tomography, radiological and histological study of osseointegration capacity

The functionality of a new metallic interbody fusion implant manufactured out of porous nitinol (PNT) was evaluated in sheep and compared to a conventional titanium intervertebral cage packed with autologous iliac crest bone. Both device types were implanted at two non-contiguous intervertebral lumbar sites. The objective was to evaluate the osseointegration capacity after 3, 6 and 12 months of implantation in the presence of these two implant types subjected to the same mechanical loads. Two-dimensional radiolology, computer tomography, and histology were used as techniques of parameters evaluation. The results indicated that PNT obtained a better intervertebral osseointegration capacity compared to the TiAlV cage. The functional difficulties of the titanium implant were related to its instability at the implantation site possibly due to a biofunctionality problem. The biocompatibility of both implants seemed however comparable.