title: A murine femoral segmental defect model for bone tissue engineering using a novel rigid internal fixation system.
abstract: BACKGROUND
  As a model animal, the mouse has already been widely used in bone-related research. However, there is a lack of ideal long bone segmental defect mouse model. Since external fixation has disadvantages of heavy weight, penetrating the skin, and hampering mobility, an internal fixation device is probably more preferable to maintain the segmental bone defect. The aim of this study was to establish a simple, reproducible, and standardized murine critical-size defect model through designing an internal fixation system, verifying its adaptability, and investigating the critical size of femoral segmental defect.
  
  
  METHODS
  By utilizing computer-aided measuring and processing system, anatomical data of adult C57BL/6 mouse femur was obtained, and a plate-bolts system was designed for rigid fixation. The plate and screws were fixed in 67 mice and 1.5 or 2.0 mm defect gaps were created in the femoral midshaft. Compression and three-point bending of bone-implant construct were tested in mice at 0, 2, 5, and 12 wk postoperative to test the biomechanical stability. X-ray, micro-computed tomography, and histology were used to investigate the defect healing process.
  
  
  RESULTS
  The plate- and screws-fitted mouse femur and unilateral or bilateral operation had seemingly no adverse impact on the mouse in general. Mechanical tests indicated that there were no significant differences between the bone-implant construct and intact femur in compression and three-point bending loading. Micro-computed tomography scanning showed the bone mineral density had not been affected by the implantation of fixation device. There was no union of the 2.0 mm segmental defect in 12-wk period.
  
  
  CONCLUSIONS
  Using the specifically designed rigid internal fixation device, a segmental defect size of 2.0 mm in C57BL/6 mouse femur will show nonunion and can serve as a critical defect size for bone tissue engineering and bone regeneration research.
authors.affiliation: The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, PR China.
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.forename: Dianqi
authors.initials: D
authors.lastname: Li
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Huang
authors.forename: Kun
authors.initials: K
authors.lastname: Lv
authors.forename: David
authors.initials: D
authors.lastname: Ongodia
authors.forename: Lingling
authors.initials: L
authors.lastname: Zhu
authors.forename: Langming
authors.initials: L
authors.lastname: Zhou
authors.forename: Zubing
authors.initials: Z
authors.lastname: Li
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods*; D017759:Fractures, Malunited / Q000000981:diagnostic imaging*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D011184:Postoperative Period; D023822:Tissue Engineering; D014057:Tomography, X-Ray Computed
keywords: Critical defect size; Femur; Internal fixation; Mouse model