title: The standardized creation of a lumbar spine vertebral compression fracture in a sheep osteoporosis model induced by ovariectomy, corticosteroid therapy and calcium/phosphorus/vitamin D-deficient diet.
abstract: BACKGROUND
  Vertebral compression fractures (VCFs) are one of the most common injuries in the aging population presenting with an annual incidence of 1.4 million new cases in Europe. Current treatment strategies focus on cement-associated solutions (kyphoplasty/vertebroplasty techniques). Specific cement-associated problems as leakage, embolism and the adjacent fracture disease are reported adding to open questions like general fracture healing properties of the osteoporotic spine. In order to analyze those queries animal models are of great interest; however, both technical difficulties in the induction of experimental osteoporosis in animal as well as the lack of a standardized fracture model impede current and future in vivo studies. This study introduces a standardized animal model of an osteoporotic VCF type A3.1 that may enable further in-depth analysis of the afore mentioned topics.
  
  
  METHODS
  Twenty-four 5-year-old female Merino sheep (mean body weight: 67 kg; range 57-79) were ovariectomized (OP1) and underwent 5.5 months of weekly corticosteroid injections (dexamethasone and dexamethasone-sodium-phosphate), adding to a calcium/phosphorus/vitamin D-deficient diet. Osteoporosis induction was documented by pQCT and micro-CT BMD (bone mineral density) as well as 3D histomorphometric analysis postoperatively of the sheep distal radius and spine. Non osteoporotic sheep served as controls. Induction of a VCF of the second lumbar vertebra was performed via a mini-lumbotomy surgical approach with a standardized manual compression mode (OP2).
  
  
  RESULTS
  PQCT analysis revealed osteoporosis of the distal radius with significantly reduced BMD values (0.19 g/cm(3), range 0.13-0.22 vs. 0.27 g/cm(3), range 0.23-0.32). Micro-CT documented significant lowering of BMD values for the second lumbar vertebrae (0.11 g/cm(3), range 0.10-0.12) in comparison to the control group (0.14 g/cm(3), range 0.12-0.17). An incomplete burst fracture type A3.1 was achieved in all cases and resulted in a significant decrease in body angle and vertebral height (KA 4.9°, range: 2-12; SI 4.5%, range: 2-12). With OP1, one minor complication (lesion of small bowel) occurred, while no complications occurred with OP2.
  
  
  CONCLUSIONS
  A suitable spinal fracture model for creation of VCFs in osteoporotic sheep was developed. The technique may promote the development of improved surgical solutions for VCF treatment in the experimental and clinical setting.
authors.affiliation: Dept. of Trauma, Hand and Reconstructive Surgery, University of Rostock, Medical Center, Germany. Electronic address: anica.eschler@med.uni-rostock.de.
authors.forename: Anica
authors.initials: A
authors.lastname: Eschler
authors.affiliation: Dept. of Trauma, Hand and Reconstructive Surgery, University of Rostock, Medical Center, Germany.
authors.forename: Paula
authors.initials: P
authors.lastname: Röpenack
authors.affiliation: Dept. of Trauma, Hand and Reconstructive Surgery, University of Rostock, Medical Center, Germany.
authors.forename: Philipp K E
authors.initials: PK
authors.lastname: Herlyn
authors.affiliation: Clinic for Anesthesiology and Critical Care Medicine, University of Rostock, Medical Center, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Roesner
authors.affiliation: Dept. of Trauma, Hand and Reconstructive Surgery, University of Rostock, Medical Center, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Pille
authors.affiliation: Chair of Nutrition Physiology and Animal Nutrition, Faculty of Agricultural and Environmental Sciences, University of Rostock, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Büsing
authors.affiliation: Rudolf-Zenker Institute for Experimental Surgery, University of Rostock, Medical Center, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Vollmar
authors.affiliation: Dept. of Trauma, Hand and Reconstructive Surgery, University of Rostock, Medical Center, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Mittlmeier
authors.affiliation: Dept. of Trauma, Orthopedic and Reconstructive Surgery, Munich Municipal Hospital Group, Clinic Harlaching, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Gradl
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D002118:Calcium / Q000172:deficiency; D004032:Diet; D004195:Disease Models, Animal; D005260:Female; D005592:Fracture Fixation / Q000379:methods*; D050815:Fractures, Compression / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D008159:Lumbar Vertebrae / Q000473:pathology*; D010024:Osteoporosis / Q000150:complications / Q000209:etiology / Q000473:pathology*; D010052:Ovariectomy; D010758:Phosphorus / Q000172:deficiency; D034561:Sheep, Domestic; D014808:Vitamin D Deficiency
chemical_list: D010758:Phosphorus; D002118:Calcium
keywords: VCF; calcium/phosphorus deficient diet; glucocorticoids; osteoporosis; pQCT; sheep model; spine Micro CT; vertebral compression fractures; μCγ