Development and Characterization of a Standard Closed Tibial Fracture Model in the Rat

Abstract

Purpose:

The aim of this study was to develop a clinically relevant standardized closed tibial fracture model in the rat and to characterize the healing process at different time points using radiologic, biomechanical, and histological methods.

Material and Methods:

The tibia and fibula were fractured in a closed manner using a guillotine-like device under standardized conditions. After closed reduction, the tibia was stabilized with an intramedullary titanium Kirschner wire. To evaluate the soft tissue trauma, the compartment pressure was measured postoperatively. To follow the healing process, X-ray examinations were performed and bridging of the calluses was scored throughout the experimental period. At 28, 42, and 84 days after fracture, animals were killed and the tibiae prepared for biomechanical torsional testing or histological and histomorphological analyses.

Results:

Only four of the 69 animals subjected to this procedure showed a complex fracture configuration. The remaining animals showed a transverse midshaft fracture (AO A2–A3) with minimal soft tissue trauma. The healing process could be detected in the radiologic investigations and showed comparable scoring parameters in all animals. The biomechanical strength increased with the healing time and showed the highest values after 84 days. The callus was composed of soft tissue, cartilage and newly formed trabecular bone after 4 weeks. At the later time points, a remodeling process was detectable with a decrease in cartilage and an increase in mineralized tissue.

Conclusion:

Since this model does not require prepinning of the bone prior to fracture, it mimics a clinical trauma setting. Using this model, the basic cellular events of fracture healing can be investigated and the effects of local or systemic factors or conditions assessed.