Fibronectin preadsorbed on hydroxyapatite together with rough surface structure increases osteoblasts' adhesion "in vitro": the theoretical usefulness of fibronectin preadsorption on hydroxyapatite to increase permanent stability and longevity in spine implants

The aim of this study was to investigate the contribution of fibronectin (FN) preadsorption to enhance osteoblast adhesion and strength on hydroxyapatite (HA) used either as osteoconductive bone substitute or precoating of pedicle screws and cages in spine surgery. HA substrata with two different surface roughness values (rough HA180 and smooth HA1200) were produced, and human osteoblasts were seeded after culturing on them. Prior to osteoblast seeding, the HA substrata were immersed in FN solution. Osteoblast attachment on each of the two HA substrata was evaluated by recording the number of cells, whereas osteoblast adhesion strength was determined by measuring the shear stress required to detach the cells from the HA substrates. FN preadsorption increased the number of attached osteoblasts on smooth and rough HA substratum at 40% and 62%, respectively, whereas it increased osteoblast attachment strength on the smooth and rough substratum at 165% and 73%, respectively. This study showed that FN preadsorption and rough HA surface texture synergistically increased "in vitro" both the number and the adhesion strength of human osteoblasts. Further studies in primates and humans should be carried out to disclose the clinical relevance (increase implant's stability and longevity) of the above-mentioned observations.