Bisphosphonate coating on titanium screws increases mechanical fixation in rat tibia after two weeks

J Biomed Mater Res A. 2008 Jul;86(1):220-7. doi: 10.1002/jbm.a.31583.


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.

MeSH terms

  • Adsorption
  • Animals
  • Coated Materials, Biocompatible*
  • Diphosphonates / chemistry*
  • Fibrinogen / chemistry*
  • Gamma Rays
  • Internal Fixators
  • Male
  • Materials Testing
  • Rats
  • Rats, Sprague-Dawley
  • Stainless Steel
  • Stress, Mechanical
  • Tibia / pathology*
  • Titanium / chemistry*


  • Coated Materials, Biocompatible
  • Diphosphonates
  • Stainless Steel
  • Fibrinogen
  • Titanium