title: Production and repair of implant-induced microdamage in the cortical bone of goats after long-term estrogen deficiency.
abstract: CONCLUSIONS
  By using an ovariectomized goat model, we found that estrogen depletion decreases bone quality and makes it susceptible to screw-induced mechanical microdamage. Both diffuse microdamage and linear cracks accumulated up to 3 weeks after screw implantation, and the microdamage was repaired gradually after 4-8 months.
  
  
  BACKGROUND
  The aim of this study was to observe the effect of long-term estrogen deficiency on the creation and repair of microdamage in cortical bone adjacent to bone screw.
  
  
  METHODS
  Cortical bone screws were placed in the tibial diaphyses 28 months after ovariectomy (OVX) or sham operation (Sham-Op) in female goats. The goats were euthanized at 0 day, 21 days, 4 months, and 8 months after screw implantation. Microdamage morphology and repair were examined in peri-screw bone using histomorphometric method, and the nanomechanical properties of peri-screw bone were examined with nanoindentation testing.
  
  
  RESULTS
  Tibiae from ovariectomized goats in which screws had been placed had significantly higher levels of diffuse microdamage and significantly more linear cracks than those from sham goats, and the diffuse microdamage was more obvious than linear cracks in the region adjacent to the implant. Both diffuse microdamage and linear cracks accumulated up to day 21 and then gradually repaired at 4 and 8 months after surgery. The trend for bone remodeling in each group was consistent with changes in the level of microdamage. Nanoindentation testing showed that both elastic modulus and hardness in peri-screw bone were significantly decreased in OVX group compared to Sham-Op group. The hardness and elastic modulus also showed a downward trend up to 4 months after screw implantation and then exhibited some recovery after 8 months.
  
  
  CONCLUSIONS
  Estrogen depletion decreases bone quality and makes it vulnerable to screw-induced mechanical damage, which may compromise the initial stability of an orthopedic implant.
authors: Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China.
authors: Z
authors: Z
authors: Yu
authors: G
authors: G
authors: Wang
authors: T
authors: T
authors: Tang
authors: L
authors: L
authors: Fu
authors: X
authors: X
authors: Yu
authors: L
authors: L
authors: Cao
authors: Z
authors: Z
authors: Zhu
authors: K
authors: K
authors: Dai
authors: S
authors: S
authors: Qiu
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D016723:Bone Remodeling / Q000502:physiology*; D001863:Bone Screws; D004195:Disease Models, Animal; D004967:Estrogens / Q000172:deficiency*; D005260:Female; D006041:Goats; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods; D015663:Osteoporosis, Postmenopausal / Q000503:physiopathology*; D010052:Ovariectomy; D013977:Tibia / Q000503:physiopathology
chemical_list: D004967:Estrogens
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