title: Changes of microstructure and mineralized tissue in the middle and late phase of osteoporotic fracture healing in rats.
abstract: BACKGROUND
  With osteoporosis emerged as one of the most important health issues, more and more investigations are focusing on osteoporotic fracture healing. However, there are few studies on the changes of microstructure and mineralized tissue of newly formed callus.
  
  
  OBJECTIVE
  We established an osteoporotic fracture rat model to evaluate the changes of microstructure and mineralized tissue during osteoporotic fracture healing.
  
  
  METHODS
  A mid-shaft femur fracture model was established 12 weeks after ovariectomy as an osteoporotic fracture group (OPF group). Femurs were then harvested at 4 weeks, 8 weeks and 12 weeks after fracture for peripheral quantitative computed tomography (pQCT), micro-computed tomography (MicroCT), histology and biomechanical test. A sham-operated group was used for comparison, i.e. the normal fracture group (NF group).
  
  
  RESULTS
  The pQCT-derived total external callus area in the OPF group was smaller than that in the NF group at 4 weeks after fracture (P<0.05), whereas it was 21% larger in the OPF group than that in the NF group at 12 weeks after fracture (P<0.01). The pQCT-derived bone mineral density in the OPF group was significantly inferior to the NF group at all the time points (P<0.05 for all the time points, respectively). MicroCT data, at 12 weeks after fracture, showed the total callus, bony callus, and newly formed bone was approximately 20% lower in the OPF group than that in the NP group, and the total connectivity was 56% lower in the OPF group as compared to the NF group. Biomechanical test data, at 12 weeks after fracture, showed that the failure load of the left femur of OPF group was 17% less compared to that of the NF group (P<0.01), and 15% lower bending stiffness (P<0.05), 20% lower bending stress (P<0.01), and 28% lower energy at failure (P<0.01) were observed in the OPF group as compared to the NF group.
  
  
  CONCLUSIONS
  The decrease in mineralized tissue and the not well connected microstructure in newly formed callus may explain the decline of mechanical impairment of fracture healing in the ovariectomized rats.
authors.affiliation: Department of Orthopaedic Surgery, 1st Affiliated Hospital, Zhengzhou University, PR China.
authors.forename: Ying-jie
authors.initials: YJ
authors.lastname: Hao
authors.forename: Hao
authors.initials: H
authors.lastname: Yingjie
authors.forename: Ge
authors.initials: G
authors.lastname: Zhang
authors.forename: Zhang
authors.initials: Z
authors.lastname: Ge
authors.forename: Yi-sheng
authors.initials: YS
authors.lastname: Wang
authors.forename: Wang
authors.initials: W
authors.lastname: Yisheng
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Qin
authors.initials: Q
authors.lastname: Ling
authors.forename: W Y
authors.initials: WY
authors.lastname: Hung
authors.forename: Kwoksui
authors.initials: K
authors.lastname: Leung
authors.forename: Leung
authors.initials: L
authors.lastname: Kwoksui
authors.forename: Fu-xing
authors.initials: FX
authors.lastname: Pei
authors.forename: Pei
authors.initials: P
authors.lastname: Fuxing
mesh_terms: D000818:Animals; D015519:Bone Density; D005260:Female; D017102:Fracture Healing; D010024:Osteoporosis / Q000473:pathology*; D010027:Osteotomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013997:Time Factors; D015898:Tomography Scanners, X-Ray Computed