Biocompatibility of sol–gel-derived titania–silica coated intramedullary NiTi nails

We investigated bone response to sol–gel-derived titania–silica coated functional intramedullary NiTi nails that applied a continuous bending force. Nails 26 mm in length, either straight or with a radius of curvature of 28 or 15 mm, were implanted in the cooled martensite form from a proximal to distal direction into the medullary cavity of the right femur in 40 Sprague–Dawley rats. Body temperature restored the austenite form, causing the curved implants to generate a bending force on the bone. The femurs were examined after 24 weeks. Bone length measurements did not reveal any bowing or shortening of the bone in the experimental groups. The results from histomorphometry demonstrated that the stronger bending force, together with sol–gel surface treatment, resulted in more bone deposition around the implant and the formation of significantly less fibrous tissue. Straight intramedullary nails, even those with a titania–silica coating, were poorly attached when compared to the implants with a curved austenite structure.