Experimental usage of hydroxyapatite preadsorption with fibronectin to increase permanent stability and longevity of spinal implants

Abstract

Hydroxyapatite has been used in orthopaedic and particularly in spinal surgery by precoating implants to indirectly increase osteoblasts' adhesion and subsequently their stability and longevity. Fibronectin preadsorption synergistically with appropriately constructed hydroxyapatite's surface texture to enhance osteoblasts' adhesion has not been, to the authors' knowledge, previously investigated. In osteoporotic spines, methods to increase implant stability (pedicle screws and cages) are of major value.

Objective: This experimental study investigated the contribution of fibronectin preadsorption to enhance osteoblasts' adhesion and strength on hydroxyapatite.

Methods: Hydroxyapatite substrata with two different surface roughnesses (rough HA180 and the smooth HA1200) were produced and human osteoblasts were seeded on them after culture. Prior to osteoblasts seeding, the hydroxyapatite substrata were immersed in fibronectin solution. Osteoblast attachment on each of the two hydroxyapatite substrata was evaluated by recording the number of cells, while the osteoblast's adhesion strength was determined by measuring the shear stress required to detach the cells from the hydroxyapatite substrates.

Results: Fibronectin preadsorption increased the number of attached osteoblasts on smooth and rough hydroxyapatite substratum at 40% and 62% respectively, while it increased osteoblast attachment strength on the smooth and rough substratum at 165% and 73% respectively.

Conclusions: Fibronectin preadsorption and smooth hydroxyapatite surface texture synergistically increased the adhesion's strength of human osteoblasts "in vitro", while preadsorption and rough hydroxyapatite surface increased the number of attached osteoblasts. Further studies in primates and human beings should be carried out to disclose the clinical relevance of the above mentioned observations in spine surgery.