title: Vertebroplasty: experimental characterization of polymethylmethacrylate bone cement spreading as a function of viscosity, bone porosity, and flow rate.
abstract: METHODS
  This is an experimental study on an artificial vertebra model and human cadaveric spine.
  
  
  OBJECTIVE
  Characterization of polymethylmethacrylate (PMMA) bone cement distribution in the vertebral body as a function of cement viscosity, bone porosity, and injection speed. Identification of relevant parameters for improved cement flow predictability and leak prevention in vertebroplasty.
  
  
  BACKGROUND
  Vertebroplasty is an efficient procedure to treat vertebral fractures and stabilize osteoporotic bone in the spine. Severe complications result from bone cement leakage into the spinal canal or the vascular system. Cement viscosity has been identified as an important parameter for leak prevention but the influence of bone structure and injection speed remain obscure.
  
  
  METHODS
  An artificial vertebra model based on open porous aluminum foam was used to simulate bone of known porosity. Fifty-six vertebroplasties with 4 different starting viscosity levels and 2 different injection speeds were performed on artificial vertebrae of 3 different porosities. A validation on a human cadaveric spine was executed. The experiments were radiographically monitored and the shape of the cement clouds quantitatively described with the 2 indicators circularity and mean cement spreading distance.
  
  
  RESULTS
  An increase in circularity and a decrease in mean cement spreading distance was observed with increasing viscosity, with the most striking change occurring between 50 and 100 Pas. Larger pores resulted in significantly reduced circularity and increased mean cement spreading distance whereas the effect of injection speed on the 2 indicators was not significant.
  
  
  CONCLUSIONS
  Viscosity is the key factor for reducing the risk of PMMA cement leakage and it should be adapted to the degree of osteoporosis encountered in each patient. It may be advisable to opt for a higher starting viscosity but to inject the material at a faster rate.
authors.affiliation: MEM Research Center, University of Bern, Switzerland.
authors.forename: Mario
authors.initials: M
authors.lastname: Loeffel
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ferguson
authors.forename: Lutz-P
authors.initials: LP
authors.lastname: Nolte
authors.forename: Jens H
authors.initials: JH
authors.lastname: Kowal
mesh_terms: D000369:Aged, 80 and over; D001843:Bone Cements / Q000737:chemistry*; D002102:Cadaver; D006801:Humans; D007267:Injections; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D008297:Male; D008953:Models, Anatomic; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000473:pathology*; D019904:Polymethyl Methacrylate / Q000008:administration & dosage / Q000737:chemistry*; D016062:Porosity; D011859:Radiography; D015203:Reproducibility of Results; D012212:Rheology; D054854:Vertebroplasty / Q000009:adverse effects; D014783:Viscosity
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate