Summit Orthopedics 1 article published in JoVE Bioengineering A Reliable and Reproducible Critical-Sized Segmental Femoral Defect Model in Rats Stabilized with a Custom External Fixator Benjamin Kerzner1, Hannah L. Martin2, Michael Weiser1, Gianluca Fontana1, Nicholas Russell1, William L. Murphy1,2, Erik A. Lund3, Christopher J. Doro1 1Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, 2Department of Biomedical Engineering, University of Wisconsin-Madison, 3Summit Orthopedics In vivo mammalian models of critical-sized bone defects are essential for researchers studying healing mechanisms and orthopedic therapies. Here, we introduce a protocol for the creation of reproducible, segmental, femoral defects in rats stabilized using external fixation.