title: The use of a side-opening injection cannula in vertebroplasty: a technical note.
abstract: METHODS
  A human cadaveric investigation was conducted to determine the effect that a side-opening injection cannula in monopedicular percutaneous vertebroplasty had on the vertebrae filling pattern.
  
  
  OBJECTIVE
  To assess the filling pattern in vertebroplasty using a monopedicular technique, and to compare a standard front-opening filling cannula with a side-opening cannula.
  
  
  BACKGROUND
  Vertebroplasty is an effective treatment for osteoporotic vertebral fractures. Clinical and biomechanical investigations show its efficacy even in asymmetrical filling patterns. However, the risk of cement extravasation is a major concern with this technique.
  
  
  METHODS
  Two different bone cement-injecting cannulas were compared: a standard front-opening cannula (8 gauge, 6 inches long) and a cannula of the same dimensions with a side-opening at its distal end. Eight pairs of osteoporotic nonfractured cadaver vertebrae (T10-T11) were augmented with low-viscosity polymethylmethacrylate under axial C-arm control. The filling pattern was assessed semiquantitatively. The cross-section in its lateral extension was divided into four equal bands, and the appearance of the cement in each respective zone was assessed after cement injections of 2, 4, and 8 mL. The extravasation of bone cement also was monitored.
  
  
  RESULTS
  With the side-opening cannula, the cement flow reached Zone 3 in six of eight cases, whereas with the front-opening cannula, the polymethylmethacrylate was observed in Zone 3 in only three cases. In no case was the cement observed in Zone 4. In five of eight cases using front-opening cannulas, extravasation into the vessels was observed after 3 to 4 mL of bone cement had been injected. No extravasation was noted with the use of the side-opening cannula unless the amount of cement exceeded 8 mL.
  
  
  CONCLUSIONS
  A side-opening cannula can improve the cement-filling pattern in monopedicular vertebroplasty, as compared with a standard front-opening cannula. The risk of extravasation is diminished if the cement flow is directed medially.
authors.affiliation: Department of Orthopaedic Surgery, Spine Service, Inselspital, University of Bern, Switzerland. paul.heini@insel.ch
authors.forename: Paul F
authors.initials: PF
authors.lastname: Heini
authors.forename: C
authors.initials: C
authors.lastname: Dain Allred
mesh_terms: D001843:Bone Cements; D002404:Catheterization / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D005119:Extravasation of Diagnostic and Therapeutic Materials / Q000517:prevention & control; D006801:Humans; D019635:Neurosurgical Procedures / Q000295:instrumentation* / Q000379:methods; D013122:Spinal Diseases / Q000601:surgery; D013131:Spine / Q000601:surgery*; D013525:Surgical Instruments / Q000592:standards*
chemical_list: D001843:Bone Cements