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Updated: Jul 9, 2026
Fracture Apparatus Design and Protocol Optimization for Closed-stabilized Fractures in Rodents
Published on: August 14, 2018
Optimization of a fracture-related infection (FRI) rat model to mimic bacterial contaminated open fractures in
Preeti J Muire1, Matthew Baldridge2, Abigail Brown2
1Department of Orthopedics and Rehabilitation, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA; Burn and Shock Trauma Research Institute, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA; Infectious Diseases and Immunology Research Institute, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
Abstract:
Open fractures are at risk for fracture-related infection (FRI) due to environmental contamination, with 40-80% of bacteria existing in biofilms. Standard treatment includes prophylactic antibiotics, surgical debridement, and irrigation; however, bacteria can persist in a biofilm/sessile form on bones and orthopedic implants. While some infections show clear clinical symptoms, others may remain subclinical for long periods. These biofilm-associated infections are difficult to treat due to their reduced susceptibility to antibiotics. This study aims to develop a clinically relevant rat model for FRI, overcoming limitations of existing models that use non-clinical materials like Polyetheretherketone (PEEK) and planktonic bacteria. By inoculating the fracture site with bacteria isolated from biofilms and utilizing stainless steel surgical implants, which are standard in clinical practice, we aim to create a more accurate representation of FRI. This improved model will provide a valuable tool for preclinical research for improving the management of FRIs, enabling the evaluation of therapeutic interventions on biofilm infections in the presence of clinically relevant implants. The experimental procedure involved creating a femur fracture in an anesthetized rat and inoculating it with 104-105 CFUs/ml Staphylococcus aureus bacteria derived from biofilms grown in vitro on glass slides for three days. The fracture was stabilized with a stainless-steel plate and screws, and the wound was closed. After one week, the anesthetized rats underwent surgical debridement and irrigation and received one dose of systemic antibiotic cefazolin. Three weeks after fracture, rats were euthanized, and the hardware and bone were harvested, washed of planktonic bacteria, and separately analyzed for CFUs. The results showed the rats demonstrated S. aureus biofilm growth in the bone and hardware with > 106 CFUs/ml. There were no differences between CFUs/ml in bone and on hardware. Our FRI model is uniquely valuable as a model for evaluating novel therapeutics against implant-associated infections.
Insights
A new rat model accurately mimics fracture-related infections (FRI) using Staphylococcus aureus biofilms and clinical implants. This model aids in testing new treatments for persistent, implant-associated bacterial infections.
Area of Science:
- Orthopedics
- Infectious Diseases
- Biomaterials Science
Background:
- Open fractures risk fracture-related infections (FRI) from bacterial biofilms on bone and implants.
- Biofilm infections are challenging to treat due to antibiotic resistance.
- Existing animal models often lack clinical relevance, using non-standard materials and planktonic bacteria.
Purpose of the Study:
- Develop a clinically relevant rat model for fracture-related infections (FRI).
- Create a model that utilizes Staphylococcus aureus biofilms and clinically used stainless steel implants.
- Provide a tool for evaluating novel therapeutic interventions against implant-associated biofilm infections.
Main Methods:
- Created a femur fracture in rats, inoculating with S. aureus biofilm.
- Stabilized fractures with stainless steel plates and screws.
- Performed surgical debridement, irrigation, and antibiotic treatment, followed by CFU analysis of bone and hardware.
Main Results:
- Successfully established S. aureus biofilm growth (>10^6 CFUs/ml) in bone and on hardware.
- No significant difference in bacterial load between bone and implant.
- The model demonstrated consistent biofilm formation, validating its efficacy.
Conclusions:
- The developed rat model accurately represents clinical fracture-related infections (FRI).
- This model is valuable for preclinical evaluation of new treatments for implant-associated infections.
- It offers a more realistic platform for studying biofilm persistence and therapeutic efficacy.
