title: Biomechanical, histological and histomorphometric analyses of calcium phosphate cement compared to PMMA for vertebral augmentation in a validated animal model.
abstract: BACKGROUND
  Calcium phosphate cements (biocements) are alternative materials for use in vertebral augmentation procedures, and are a potential solution to problems associated with polymethylmethacrylate (PMMA) cements. The aim of this study is to demonstrate the utility of percutaneously injected biocements compared with PMMA in a validated animal model of osteoporosis.
  
  
  METHODS
  Fortyseven augmentation procedures were performed on 11 osteoporotic sheep. 9 vertebrae were augmented with PMMA and 38 with a biocement. The animals were killed in four groups: at 7 days, 3 months, 6 months, and 1 year after intervention. Radiological study and TC of the pieces were obtained to evaluate for leakage, cement diffusion, and integration. In total, 26 biomechanic studies and 27 histomorphometry analyses were performed, included control vertebrae.
  
  
  RESULTS
  In 20.9% of the vertebrae, the hole was empty at sacrifice. The pattern of fracture was heterogeneous, and cement augmentation did not increase vertebral strength or decrease vertebral stiffness compared to control vertebrae, with neither PMMA or biocement. The rate of remodeling of the biocement was not predictable. In the single majority, there is peripheral remodeling, staying the volume of injected biocement stable.
  
  
  CONCLUSIONS
  Even though this animal model may not be useful to analyze the biomechanical pattern of treated vertebrae, it demonstrates that the percutaneous use of biocements in vertebral augmentation techniques is not predictable. This is one reason not to recommend its use presently as a substitute for PMMA in vertebral reinforcement procedures.
authors.affiliation: Spine Service, Fundación Jiménez DÍaz, Av Reyes Católicos, 2, 28040, Madrid, Spain. lalvarez@fjd.es
authors.forename: Luis Alvarez
authors.initials: LA
authors.lastname: Galovich
authors.forename: Antonio
authors.initials: A
authors.lastname: Perez-Higueras
authors.forename: Jose R
authors.initials: JR
authors.lastname: Altonaga
authors.forename: José Manuel Gonzalo
authors.initials: JM
authors.lastname: Orden
authors.forename: Maria Lluisa Mariñoso
authors.initials: ML
authors.lastname: Barba
authors.forename: Maria Teresa Carrascal
authors.initials: MT
authors.lastname: Morillo
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D001843:Bone Cements / Q000494:pharmacology*; D002130:Calcium Phosphates / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D010024:Osteoporosis / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D019904:Polymethyl Methacrylate / Q000494:pharmacology*; D012756:Sheep; D013131:Spine / Q000473:pathology / Q000502:physiology / Q000601:surgery; D054854:Vertebroplasty / Q000379:methods*
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D019904:Polymethyl Methacrylate; C020243:calcium phosphate