title: Ex vivo evaluation of the polymerization temperatures during cement augmentation of proximal femoral nail antirotation blades.
abstract: BACKGROUND
  Previous studies have clearly demonstrated superior biomechanical behavior of augmented proximal femoral nail antirotation (PFNA) blades compared with nonaugmented ones with respect to implant cutout. Nevertheless, there is concern about thermal bone necrosis due to exothermic curing of polymethylmethacrylate (PMMA)-based bone cements. The objective of this study was to quantify the temperatures arising around perforated titanium PFNA blades when augmenting with PMMA.
  
  
  METHODS
  Cylindrical samples from six pairs of fresh frozen human cadaveric femoral heads implanted with a PFNA blade were placed in a 37°C water bath and augmented with 3 mL and 6 mL PMMA. During augmentation, temperatures were measured using six K-type thermocouples that were placed at controlled distances around the implant. With the help of high-resolution quantitative computed tomography images, the locations of all thermocouples with respect to the cement-bone interface were reconstructed.
  
  
  RESULTS
  No temperatures higher than 45°C were measured in the interface region and the surrounding cement-free cancellous bone. In the same regions, the longest exposure time above 41°C was 8.5 minutes and was measured in a 6-mL sample. Average maximum temperature was significantly lower for the 3-mL group compared with the 6-mL group (p = 0.017).
  
  
  CONCLUSIONS
  The results of this study suggest that augmentation of titanium PFNA blades is not associated with a risk of thermal bone necrosis when using up to 6 mL of PMMA. However, larger amounts of cement lead to higher temperatures. PMMA application should therefore be kept low to minimally alter the biological system.
authors.affiliation: Biomedical Services, AO Research Institute, Davos, Switzerland. ladina.fliri@aofoundation.org
authors.forename: Ladina
authors.initials: L
authors.lastname: Fliri
authors.forename: Mark
authors.initials: M
authors.lastname: Lenz
authors.forename: Andreas
authors.initials: A
authors.lastname: Boger
authors.forename: Markus
authors.initials: M
authors.lastname: Windolf
mesh_terms: D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D001858:Bone Nails; D005264:Femoral Fractures / Q000601:surgery*; D005269:Femur / Q000601:surgery; D006801:Humans; D058105:Polymerization; D019904:Polymethyl Methacrylate; D013696:Temperature
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate