title: Antibiotic distribution in a bone cement spacer model.
abstract: OBJECTIVE
  To mix high dose antibiotic powder to the bone cement more easily, Hanssen et al reported mixing the antibiotics with the cement during its liquid phase but made no comments about the relevance of cement viscosity and antibiotic distribution. The purpose of this study was to investigate the effect of the cement mixing technique and cement viscosity on the antibiotics distribution in a cement spacer model.
  
  
  METHODS
  Thirty cylindrical models from three groups were examined. Group A was made by mixing the antibiotics with medium viscosity cement prior to adding the liquid monomer (traditional technique). Group B was made by mixing the antibiotics with medium viscosity cement during its liquid phase (Hanssen's technique). Group C was made by traditional technique with low viscosity cement. In all groups 2 g of tetracycline was used. Three 0.1 mm thick cross sections from each spacer model were examined under the fluorescent microscope. The fluorescent spots of tetracycline were calculated automatically in pixels. To evaluate the distribution of the antibiotics in the spacer model, we selected the cross section with the highest number of pixels and the one with the lowest number of pixels from each of the three cross sections and calculated the difference between them. The distribution disequilibrium was compared between group A and B, A and C.
  
  
  RESULTS
  No significant difference was observed in either comparison.
  
  
  CONCLUSIONS
  The Hanssen's mixing technique can be used when using high dose antibiotics, and either medium or low viscosity cement could be used in terms of antibiotic distribution.
authors.affiliation: Surgical and Orthopaedic Research Laboratories, University of New South Wales, Prince of Wales Hospital, Randwick, NSW, Australia. keishiramizu@gmail.com
authors.forename: K
authors.initials: K
authors.lastname: Shiramizu
authors.forename: V
authors.initials: V
authors.lastname: Lovric
authors.forename: A M D
authors.initials: AM
authors.lastname: Leung
authors.forename: W R
authors.initials: WR
authors.lastname: Walsh