title: High-viscosity cement significantly enhances uniformity of cement filling in vertebroplasty: an experimental model and study on cement leakage.
abstract: METHODS
  Experimental study using a laboratory leakage model.
  
  
  OBJECTIVE
  To examine the working hypothesis that high-viscosity cements will spread uniformly, thus significantly reducing the risk of leakage.
  
  
  BACKGROUND
  In vertebroplasty, forces that govern the flow of bone cement in the trabecular bone skeleton are an essential determinant of the uniformity of cement filling. Extraosseous cement leakage has been reported to be a major complication of this procedure. Leakage occurs due to the presence of a path of least resistance caused by irregularities in the trabecular bone or shell structure. Ideally, cement uniformly infiltrates the trabecular bone skeleton and does not favor specific paths. Cement viscosity is believed to affect the infiltration forces and flow during the procedure. Clinically, altering the time between cement mixing and delivery modifies the viscosity of bone cement.
  
  
  METHODS
  An experimental model of the leakage phenomenon of vertebroplasty was developed. A path, simulating a blood vessel, was created in the model to perturb the forces underlying cement flow and to favor leakage. Cement of varying viscosities was injected in the model, and, thereafter, the filling pattern, cement mass that has leaked, time at which leakage occurred, and injection pressure were measured.
  
  
  RESULTS
  A strong relationship was found between the uniformity of the filling pattern and the elapsed time from cement mixing and viscosity, respectively. Specifically, 3 distinct cement leakage patterns were observed: immediate leakage was observed when cement was injected 5-7 minutes following mixing. The cement was of a low viscosity and more than 50% of the total cement injected leaked. Moderate leakage was observed when injection occurred 7-10 minutes following mixing. Less than 10% of the cement leaked, and the viscosity was at a transient state between the low viscosity of immediate leakage and a higher viscosity, doughy cement. Cement leakage ceased completely when cement was delivered after 10 minutes. The viscosity of the cement in this case was high, and the cement was of a dough-like consistency.
  
  
  CONCLUSIONS
  High-viscosity cement seems to stabilize cement flow. However, the forces required for the delivery of high-viscosity cement may approach or exceed the human physical limit of injection forces. Although the working time of the cement is about 17 minutes, it may not be manually injectable with a standard syringe and cannula after 10 minutes, at which time cement leakage ceased completely.
authors.affiliation: Biomechanics Laboratory, Mechanical Engineering Department, Université de Sherbrooke, 2500 boul. de l'Université, Sherbrooke, Quebec, Canada J1K 2R1. Gamal.Baroud@Usherbrooke.ca
authors.forename: Gamal
authors.initials: G
authors.lastname: Baroud
authors.forename: Meghan
authors.initials: M
authors.lastname: Crookshank
authors.forename: Marc
authors.initials: M
authors.lastname: Bohner
mesh_terms: D001696:Biomechanical Phenomena / Q000295:instrumentation / Q000379:methods / Q000592:standards; D001843:Bone Cements / Q000494:pharmacology / Q000592:standards; D002484:Cementation / Q000295:instrumentation / Q000379:methods / Q000592:standards; D008422:Materials Testing / Q000295:instrumentation* / Q000379:methods* / Q000592:standards; D008953:Models, Anatomic; D016062:Porosity; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D014783:Viscosity
chemical_list: D001843:Bone Cements