title: A versatile model of open-fracture infection : a contaminated segmental rat femur defect.
abstract: OBJECTIVE
  The purpose of this study was to refine an accepted contaminated rat femur defect model to result in an infection rate of approximately 50%. This threshold will allow examination of treatments aimed at reducing infection in open fractures with less risk of type II error.
  
  
  METHODS
  Defects were created in the stablised femurs of anaethetised rats, contaminated with Staphylococcus aureus and then debrided and irrigated six hours later. After 14 days, the bone and implants were harvested for separate microbiological analysis. This basic model was developed in several studies by varying the quantity of bacterial inoculation, introducing various doses of systemic antibiotics with and without local antibiotics.
  
  
  RESULTS
  The bacterial inoculation associated with a 50% infection rate was established as 1 × 10(2) colony forming units (CFU). With an initial bacterial inoculum of 1 × 10(5) CFU, the dose of systemic antibiotics associated with 50% infection was 5 mg/Kg of cafazolin injected sub-cutaneously every 12 hours, starting at the time of the first debridment and continuing for 72 hours (seven doses). The systemic dose of cafazolin was lowered to 2 mg/Kg when antibiotic polymethyl methacrylate beads were used concurrently with the same amount of bacterial inoculation.
  
  
  CONCLUSIONS
  This model of open fracture infection has been further refined with potential for local and systemic antibiotics. This is a versatile model and with the concepts presented herein, it can be modified to evaluate various emerging therapies and concepts for open fractures. Cite this article: Bone Joint Res 2014;3:187-92.
authors.affiliation: Royal Centre for Defence Medicine, Academic Department of Military Surgery and Trauma, Birmingham, UK.
authors.forename: J G
authors.initials: JG
authors.lastname: Penn-Barwell
authors.affiliation: Royal Centre for Defence Medicine, Academic Department of Military Surgery and Trauma, Birmingham, UK.
authors.forename: B C C
authors.initials: BC
authors.lastname: Rand
authors.affiliation: Royal Centre for Defence Medicine, Academic Department of Military Surgery and Trauma, Birmingham, UK.
authors.forename: K V
authors.initials: KV
authors.lastname: Brown
authors.affiliation: Royal Centre for Defence Medicine, Academic Department of Military Surgery and Trauma, Birmingham, UK. 1US Army Institute of Surgical Research, 3698 Chambers Pass, Fort Sam Houston, San Antonio, Texas, 78234, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Wenke
keywords: Infection; Open fracture; Contamination; Animal-model; Local antibiotics