title: The effect of surface material and roughness on bone screw stability.
abstract: OBJECTIVE
  To evaluate the effects of osteointegration ability and surface texture on bone screw interface stability in three different groups of titanium screws.
  
  
  METHODS
  Sixty titanium tapered screws were used: twenty screws were polished, uncoated (Group A); twenty screws were rough, coated with titanium (Group B); and twenty screws were rough, coated with fluor-hydroxyapatite (Group C). Thirty screws, ten per group, were implanted in the femurs and tibiae of two sheep, which were euthanized one month after surgery. The remaining thirty screws, ten per group, were implanted in the femurs and tibiae of another two sheep, which were euthanized three months after surgery.
  
  
  RESULTS
  At one month, extraction torque of Group C was higher than that of Group A (p = 0.042). At three months, extraction torque of Group C was higher than that of Group A (p < 0.0001) and Group B (p < 0.0001). At three months, extraction torque of Group C was higher compared with the corresponding insertion torque (p < 0.0001) and compared with the corresponding extraction torque at one month (p < 0.0001). At one and three months, a high percentage of bone-screw contact was observed histologically in Groups B and C. A continuous gap with fibrous tissue encapsulation was observed in Group A.
  
  
  CONCLUSIONS
  This study shows that the osteointegration ability provided by the type of coating is a very important parameter for optimizing the bone-screw stability. Surface texture is also important. By using screws with optimal osteointegration ability, very positive clinical consequences can be expected.
authors.affiliation: Department of Orthopaedic Surgery, Bologna University, Rizzoli Orthopaedic Institute, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Moroni
authors.forename: C
authors.initials: C
authors.lastname: Faldini
authors.forename: V
authors.initials: V
authors.lastname: Chilò
authors.forename: M
authors.initials: M
authors.lastname: Rocca
authors.forename: S
authors.initials: S
authors.lastname: Stea
authors.forename: S
authors.initials: S
authors.lastname: Giannini
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005260:Female; D006882:Hydroxyapatites; D017665:Hydroxyl Radical; D008422:Materials Testing; D016348:Osseointegration; D019736:Prostheses and Implants; D011474:Prosthesis Design; D012756:Sheep; D014025:Titanium
chemical_list: D006882:Hydroxyapatites; D017665:Hydroxyl Radical; C028869:fluor-hydroxylapatite; D014025:Titanium