title: Enhanced wound healing associated with Sharpey's fiber-like tissue formation around FGF-2-apatite composite layers on percutaneous titanium screws in rabbits.
abstract: BACKGROUND
  Pin-tract infections are the most common complications of external fixation. To solve the problem, we developed a fibroblast growth factor-2 (FGF-2)-apatite composite layer for coating titanium screws. The purpose of this study was to elucidate the mechanism of the improvement in infection resistance associated with FGF-2-apatite composite layers.
  
  
  METHODS
  We analyzed FGF-2 release from the FGF-2-apatite composite layer and the mitogenic activity of the FGF-2-apatite composite layer. We evaluated time-dependent development of macroscopic pin-tract infection around uncoated titanium control screws (n = 10). Screws coated with the apatite layer (n = 16) and FGF-2-apatite composite layer (n = 16) were percutaneously implanted for 4 weeks in the medial proximal tibia in rabbits.
  
  
  RESULTS
  A FGF-2-apatite composite layer coated on the screws led to the retention of the mitogenic activity of FGF-2. FGF-2 was released from the FGF-2-apatite composite layer in vitro for at least 4 days, which corresponds to a period when 30% of pin-tract infections develop macroscopically in the percutaneous implantation of uncoated titanium control screws. The macroscopic infection rate increased with time, reaching a plateau of 80-90% within 12 days. This value remained unchanged until 4 weeks after implantation. The screws coated with an FGF-2-apatite composite layer showed a significantly higher wound healing rate than those coated with an apatite layer (31.25 vs. 6.25%, p < 0.05). The interfacial soft tissue that bonded to the FGF-2-apatite composite layer is a Sharpey's fiber-like tissue, where collagen fibers are inclined at angles from 30 to 40° to the screw surface. The Sharpey's Wber-like tissue is rich in blood vessels and directly bonds to the FGF-2-apatite composite layer via a thin cell monolayer (0.8-1.7 μm thick).
  
  
  CONCLUSIONS
  It is suggested that the enhanced wound healing associated with the formation of Sharpey's fiber-like tissue triggered by FGF-2 released from the FGF-2-apatite composite layer leads to the reduction in the pin-tract inflammation rate.
authors: Department of Orthopaedic Surgery, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan. mutsuzaki@ipu.ac.jp
authors: Hirotaka
authors: H
authors: Mutsuzaki
authors: Atsuo
authors: A
authors: Ito
authors: Yu
authors: Y
authors: Sogo
authors: Masataka
authors: M
authors: Sakane
authors: Ayako
authors: A
authors: Oyane
authors: Naoyuki
authors: N
authors: Ochiai
mesh_terms: D000818:Animals; D001031:Apatites; D001863:Bone Screws; D016267:External Fixators; D016222:Fibroblast Growth Factor 2 / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D005347:Fibroblasts / Q000187:drug effects; D005592:Fracture Fixation / Q000295:instrumentation*; D008297:Male; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D041681:NIH 3T3 Cells; D011474:Prosthesis Design; D016459:Prosthesis-Related Infections / Q000517:prevention & control*; D011817:Rabbits; D013977:Tibia / Q000601:surgery; D014025:Titanium; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D001031:Apatites; D016222:Fibroblast Growth Factor 2; D014025:Titanium