title: Osseous integration of calcium phosphate in osteoporotic vertebral fractures after kyphoplasty: initial results from a clinical and experimental pilot study.
abstract: BACKGROUND
  This study evaluated the radiological changes at the bone-cement interface of calcium phosphate cement (CPC) and polymethylmethacrylate (PMMA) 12 months after kyphoplasty. In a pilot experiment, we additionally performed a histomorphometric analysis in osteopenic foxhounds to analyze the process of osseous integration of CPC and PMMA.
  
  
  METHODS
  Twenty postmenopausal female patients with 46 vertebral compression fractures (VCF) were treated by kyphoplasty, utilizing CPC (N=28) or PMMA (N=18) for intravertebral stabilization. After a 12-month follow-up, we measured the density changes of border voxels at the bone-cement interface by computed tomography (CT) using dedicated software algorithms. We defined the border-voxel density (BVD) as a parameter of cement resorption at the interface. We also investigated the bone-implant interface in three osteopenic foxhounds by histomorphometry 3, 6, and 12 months after cement implantation.
  
  
  RESULTS
  Twelve months after kyphoplasty, only CPC showed a significant decrease of the BVD compared to PMMA (p<0.01), indicating a slow progress of resorption at the interface. Histomorphometry of the dog vertebrae showed near total bone coverage of CPC implants, whereas the PMMA surface exhibited only 30% direct bone contact (p<0.01). We also observed a time-dependent increase in the number of discernable osteons close to the interface of CPC, but no bone tissue within PMMA (p<0.01).
  
  
  CONCLUSIONS
  The decrease of the BVD 12 months after kyphoplasty may indicate osseous integration of CPC by: (1) the ingrowth of bone tissue and (2) osteonal penetration close to the interface.
authors.affiliation: Department of Diagnostic Radiology, University of Heidelberg, Heidelberg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Libicher
authors.forename: J
authors.initials: J
authors.lastname: Hillmeier
authors.forename: U
authors.initials: U
authors.lastname: Liegibel
authors.forename: U
authors.initials: U
authors.lastname: Sommer
authors.forename: W
authors.initials: W
authors.lastname: Pyerin
authors.forename: M
authors.initials: M
authors.lastname: Vetter
authors.forename: H-P
authors.initials: HP
authors.lastname: Meinzer
authors.forename: I
authors.initials: I
authors.lastname: Grafe
authors.forename: P
authors.initials: P
authors.lastname: Meeder
authors.forename: G
authors.initials: G
authors.lastname: Nöldge
authors.forename: P
authors.initials: P
authors.lastname: Nawroth
authors.forename: C
authors.initials: C
authors.lastname: Kasperk
mesh_terms: D000818:Animals; D001843:Bone Cements / Q000378:metabolism*; D002130:Calcium Phosphates / Q000378:metabolism*; D004285:Dogs; D005260:Female; D050815:Fractures, Compression / Q000601:surgery*; D006801:Humans; D016348:Osseointegration; D010024:Osteoporosis / Q000473:pathology / Q000601:surgery*; D010865:Pilot Projects; D019904:Polymethyl Methacrylate; D016103:Spinal Fractures / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D019904:Polymethyl Methacrylate; C020243:calcium phosphate