Rat Calvarial Defect Models in Bone Regeneration Research: A Narrative Review of Critical Size and Micro-Computed Tomography Outcome Reporting

Abstract

Simple Summary Rat skull defects are widely used to test methods intended to improve bone healing, but researchers need reliable information about which defects heal naturally and how healing should be measured. We reviewed published studies of untreated rat skull defects, focusing on defect size and three-dimensional X-ray imaging used to measure new bone. Defects smaller than 5 mm often healed only partly, suggesting that even these smaller defects may be critical-sized under certain experimental conditions. Reported healing varied greatly between studies because animal characteristics, surgeries, observation times, imaging settings, and outcome definitions were not consistent. Many studies also failed to provide numerical data that could be reused. Future studies should use the least severe defect that can answer the research question, justify animal numbers and procedures, and report imaging methods and numerical outcomes clearly. Better planning and reporting can improve reproducibility, reduce unnecessary repetition, and increase the knowledge gained from each animal.