title: Evaluation of porous gradient hydroxyapatite/zirconia composites for repair of lumbar vertebra defect in dogs.
abstract: OBJECTIVE
  To evaluate the effects of porous gradient composites with hydroxyapatite/zirconia and autologous iliac in repair of lumbar vertebra body defects in dogs.
  
  
  METHODS
  (1) New porous gradient hydroxyapatite/zirconia composites were prepared using foam immersion, gradient compound and high temperature sintering; (2) A total of 18 adult beagle dogs, aged five to eight months and weighted 10-13 kg, were randomly assigned into two subgroups, which were implanted with new porous gradient hydroxyapatite/zirconia composites (subgroup A in 12) or autologous iliac bone (subgroup B in 6); (3) The post-operative data were analyzed and compared between the subgroups to repair the vertebral body defect by roentgenoscopy, morphology and biomechanics.
  
  
  RESULTS
  The porosity of new porous gradient hydroxyapatite/zirconia composites is at 25 poles per inch, and the size of pores is at between 150 and 300 µm. The post-operative roentgenoscopy displayed that new-bone formation is increased gradually, and the interface between composites and host-bone becomes became blur, and the new-bone around the composites were integrated into host-bone at 24 weeks postoperatively in subgroup A. As to subgroup B, the resorption and restructure were found at six weeks after the surgery, and the graft-bone and host-bone have been integrated completely without obvious boundary at 24 weeks postoperatively. Histomorphologic study showed that the amount of bone within pores of the porous gradient hydroxyapatite/zirconia composites increased continuously with a prolonged implantation time, and that partial composites were degradated and replaced by new-bone trabeculae. There was no significant difference between subgroups (P > 0.05) in the ultimate compressive strengths.
  
  
  CONCLUSIONS
  New porous gradient hydroxyapatite/zirconia composites can promote the repair of bony defect, and induce bone tissue to ingrow into the pores, which may be applied widely to the treatment of bony defect in the future.
authors.affiliation: Research Institute of Orthopedics, Zhejiang Chinese Medical University, Zhejiang, China spinequan@yahoo.com.
authors.forename: Rong-Xue
authors.initials: RX
authors.lastname: Shao
authors.affiliation: Department of Orthopedics, Xiaoshan Traditional Chinese Medical Hospital, Zhejiang, China.
authors.forename: Ren-Fu
authors.initials: RF
authors.lastname: Quan
authors.affiliation: Research Institute of Orthopedics, Zhejiang Chinese Medical University, Zhejiang, China.
authors.forename: Xiao-Long
authors.initials: XL
authors.lastname: Huang
authors.affiliation: Research Institute of Orthopedics, Zhejiang Chinese Medical University, Zhejiang, China.
authors.forename: Tuo
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Orthopedics, Xiaoshan Traditional Chinese Medical Hospital, Zhejiang, China.
authors.forename: Shang-Ju
authors.initials: SJ
authors.lastname: Xie
authors.affiliation: Yunnan University of Traditional Chinese Medicine, YunNan, China.
authors.forename: Huan-Huan
authors.initials: HH
authors.lastname: Gao
authors.affiliation: School of Materials Science and Engineering, Shanghai University, Shanghai, China.
authors.forename: Xi-Cheng
authors.initials: XC
authors.lastname: Wei
authors.affiliation: Department of Orthopedics, The Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou, China.
authors.forename: Di-Sheng
authors.initials: DS
authors.lastname: Yang
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D018786:Bone Substitutes / Q000737:chemistry*; D019245:Compressive Strength; D004285:Dogs; D017886:Durapatite / Q000737:chemistry*; D017102:Fracture Healing; D008159:Lumbar Vertebrae / Q000293:injuries / Q000502:physiology* / Q000601:surgery* / Q000648:ultrastructure; D010012:Osteogenesis; D016062:Porosity; D015040:Zirconium / Q000737:chemistry*
chemical_list: D018786:Bone Substitutes; D017886:Durapatite; D015040:Zirconium; C028541:zirconium oxide
keywords: Hydroxyapatites; artificial vertebrae; bone tissue engineering; composite; zirconia