Minimal invasive open tibial fracture model in mice

Fracture models in animals are essential to analyze bone healing in musculoskeletal research fields. Especially in small animals, fractures are difficult to simulate and stabilize. Therefore, a fracture model is desirable with a short operation time, high safety of the model without stabilization failure and low costs. Aim of this study is the evaluation of a new open tibial shaft model in mice for musculoskeletal research.

In 12 eight week-old wild type mice, an open tibial shaft fracture was simulated and stabilized with a retrograde over the fracture inserted intramedullary pin. X-rays confirmed the correct fracture localization and stabilization. After eight weeks of follow-up, the mice were euthanized. Fracture healing and biomechanical stability were analyzed in a micro-CT scan and in torsional load-to-failure tests.

The whole operations lasted in mean eight min and 50 s. All mice recovered very quickly after the operative intervention and started using the operated leg again on the first postoperative day onwards if not earlier. No infections or failure of the stabilization occurred. All fractures healed completely within 8 weeks and substantial callus formation was confirmed in the micro-CT analysis. Biomechanically, higher torsional moment and stiffness were found for the operated tibia compared to the non-operated tibia in the same mouse.

The presented tibial fracture model with open osteotomy and retrograde pin insertion revealed minimal operative intervention and anesthesia, quick recovery and fracture healing with big callus formation. It is an easy to address fracture model for musculoskeletal research.