LAUSR

he first few weeks during which inflammation and T revascularization occur are likely the most critical ones to bone healing. Surface, chemical, and structural modifications can be made to encourage early granulation formation, and to promote the progression of bone healing past the inflammatory phase by encouraging the differentiation of local stem cells and osteoprogenitors into osteoblasts. Extensive experience in total joints has demonstrated that titanium (Ti) is particularly conducive to osseointegration. Previously, it was thought that once the surface of the Ti rapidly oxidizes in the body, it becomes nonreactive. Recent data suggest that a chemical reaction between oxidized Ti and calcium phosphate is possible. This reaction is responsible for osseointegration at the chemical level. However, promoting bone growth and remodeling across a large distance such as the intervertebral space may require temporally different signaling than that provided by traditional Ti surface treatments and hydroxyapatite coatings. Extensive research has shown that osseointegration can be enhanced by changing roughness or coating Ti with a ceramic such as hydroxyapatite, but only more recently have the cellular effects of surface topography in the nanoscale range been described. When Ti is placed in an electrolyte solution and subjected to electrochemical anodization, nanotubular arrays of Ti oxide can self-assemble on the surface. Tubular arrays in