Surgical procedures and experimental outcomes of closed fractures in rodent models

The closed fracture rat model, first described by Bonnarens and Einhorn, has been widely implemented in recent years to characterize various fracture phenotypes and evaluate treatment modalities. Slight modifications in the fixation depth, to reduce surgical error associated with movement/dislocation of the k-wire fixation, were previously described. Here, we describe this method which involves the creation of a medial parapatellar incision, dislocation of the patella, boring an 18 gauge hole through the center of the femur, delivery of an adjunct (if applicable), fixation of the k-wire in the greater trochanter of the femur, suturing of muscle and skin, and finally creation of the mid-diaphyseal fracture with a three-point bending fracture device. Many laboratories routinely perform surgical procedures in which a closed fracture is induced using rat or mouse models. The benefits of such surgical models range from general orthopaedic trauma applications to the assessment of the healing process in genetically modified animals. Other important applications include the assessment of the safety and efficacy of various treatment modalities as well as the characterization of bone repair in metabolic bone diseases or skeletal dysplasia.