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Updated: Jun 30, 2025
Calvarial Model of Bone Augmentation in Rabbit for Assessment of Bone Growth and Neovascularization in Bone Substitution Materials
Published on: August 13, 2019
Implant retention in a rabbit model of fracture-related infection
Jan Puetzler1,2, Alejandro Vallejo Diaz1,3,4, Georg Gosheger2
1AO Research Institute Davos, Davos, Switzerland.
Aims:
Fracture-related infection (FRI) is commonly classified based on the time of onset of symptoms. Early infections (< two weeks) are treated with debridement, antibiotics, and implant retention (DAIR). For late infections (> ten weeks), guidelines recommend implant removal due to tolerant biofilms. For delayed infections (two to ten weeks), recommendations are unclear. In this study we compared infection clearance and bone healing in early and delayed FRI treated with DAIR in a rabbit model.
Methods:
Staphylococcus aureus was inoculated into a humeral osteotomy in 17 rabbits after plate osteosynthesis. Infection developed for one week (early group, n = 6) or four weeks (delayed group, n = 6) before DAIR (systemic antibiotics: two weeks, nafcillin + rifampin; four weeks, levofloxacin + rifampin). A control group (n = 5) received revision surgery after four weeks without antibiotics. Bacteriology of humerus, soft-tissue, and implants was performed seven weeks after revision surgery. Bone healing was assessed using a modified radiological union scale in tibial fractures (mRUST).
Results:
Greater bacterial burden in the early group compared to the delayed and control groups at revision surgery indicates a retraction of the infection from one to four weeks. Infection was cleared in all animals in the early and delayed groups at euthanasia, but not in the control group. Osteotomies healed in the early group, but bone healing was significantly compromised in the delayed and control groups.
Conclusion:
The duration of the infection from one to four weeks does not impact the success of infection clearance in this model. Bone healing, however, is impaired as the duration of the infection increases.
Insights
Early fracture-related infections (FRI) treated with debridement, antibiotics, and implant retention (DAIR) showed successful infection clearance. However, prolonged infection duration before DAIR negatively impacted bone healing in this rabbit model.
Area of Science:
- Orthopedic surgery
- Infectious diseases
- Biomedical engineering
Background:
- Fracture-related infection (FRI) classification varies by onset time, impacting treatment strategies.
- Early FRI (<2 weeks) typically treated with debridement, antibiotics, and implant retention (DAIR).
- Late FRI (>10 weeks) guidelines recommend implant removal due to biofilms; delayed FRI (2-10 weeks) lacks clear recommendations.
Purpose of the Study:
- To compare infection clearance and bone healing in early versus delayed FRI treated with DAIR.
- To evaluate the impact of infection duration on treatment outcomes in a rabbit model.
Main Methods:
- Staphylococcus aureus inoculated into humeral osteotomies in rabbits.
- Two groups: early infection (1 week) and delayed infection (4 weeks) before DAIR.
- DAIR involved systemic antibiotics; control group received revision surgery without antibiotics. Bacteriology and radiological bone healing (mRUST) assessed.
Main Results:
- Infection cleared in all early and delayed FRI groups post-DAIR, but not in the control group.
- Greater initial bacterial burden in the early group compared to delayed and control.
- Bone healing occurred in the early FRI group but was significantly compromised in delayed FRI and control groups.
Conclusions:
- Infection duration from one to four weeks did not affect infection clearance success with DAIR in this model.
- Increasing infection duration prior to DAIR significantly impairs bone healing outcomes.
