Utilization of the AO LockingRatNail in a novel rat femur critical defect model.

ABSTRACTBackground: Our objective was to utilize a commercially available rodent locked intramedullary nail in a rat femur diaphyseal defect. This model is needed for future studies where materials in the critical defect could be modified with agents to fight infection (antibiotics) or promote osteogenesis. Methods: After unsatisfactory attempts to develop a reliable femur critical size defect model utilizing various forms of fixation, a locked intramedullary nailing system (AO LockingRatNail) was employed in 105 male Sprague Dawley rats. A 5 mm critical size mid-diaphyseal femoral defect was created using a pneumatic sagittal saw. The intramedullary nail was placed in the femur in a retrograde manner. A prefabricated polymethyl-methacrylate (PMMA) spacer was utilized to fill the defect. Once adequate alignment was achieved, two locking pegs were placed (one distal, one proximal) to provide stable fixation. Results: The technique was successful in 90% of femurs (95 of 105). The majority of complications c...