title: Bisphosphonate coating on titanium screws increases mechanical fixation in rat tibia after two weeks.
abstract: Recently published data indicate that immobilized N-bisphosphonate enhances the pullout force and energy uptake of implanted stainless steel screws at 2 weeks in rat tibia. This study compares titanium screws with and without a bisphosphonate coating in the same animal model. The screws were first coated with an approximately 100-nm thick crosslinked fibrinogen film. Pamidronate was subsequently immobilized into this film via EDC/NHS-activated carboxyl groups within the fibrinogen matrix, and finally another N-bisphosphonate, ibandronate, was physically adsorbed. The release kinetics of immobilized (14)C-alendronate was measured in buffer up to 724 h and showed a 60% release within 8 h. Mechanical tests demonstrated a 32% (p = 0.04) and 48% (p = 0.02) larger pullout force and energy until failure after 2 weeks of implantation, compared to uncoated titanium screws. A control study with physically adsorbed pamidronate showed no effect on mechanical fixation, probably due to a too small adsorbed amount. We conclude that the fixation of titanium implants in bone can be improved by fibrinogen matrix-bound bisphosphonates.
authors.affiliation: Division of Orthopaedics, Department of Neuroscience and Locomotion, Faculty of Health Sciences, Linköping University, SE-581 85 Linköping, Sweden. karwe@inr.liu.se
authors.forename: Karin
authors.initials: K
authors.lastname: Wermelin
authors.forename: Per
authors.initials: P
authors.lastname: Aspenberg
authors.forename: Paula
authors.initials: P
authors.lastname: Linderbäck
authors.forename: Pentti
authors.initials: P
authors.lastname: Tengvall
mesh_terms: D000327:Adsorption; D000818:Animals; D020099:Coated Materials, Biocompatible; D004164:Diphosphonates / Q000737:chemistry*; D005340:Fibrinogen / Q000737:chemistry*; D005720:Gamma Rays; D016268:Internal Fixators; D008297:Male; D008422:Materials Testing; D051381:Rats; D017207:Rats, Sprague-Dawley; D013193:Stainless Steel; D013314:Stress, Mechanical; D013977:Tibia / Q000473:pathology*; D014025:Titanium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D004164:Diphosphonates; D013193:Stainless Steel; D005340:Fibrinogen; D014025:Titanium