Abstract
<title>Abstract</title> <p> Background Odontoid fractures are common injury of the cervical spine and are closely linked to the microstructural characteristics of the surrounding bone. This research quantitatively examined three-dimensional differences in the trabecular architecture of normal odontoid processes, classified according to the Anderson-D' Alonzo fracture system, using high-resolution micro-computed tomography. By including samples from developing bones, the study evaluated how these structural features affect susceptibility to specific fracture types and highlighted the structural basis of fracture risk. Methods To assess these structural differences, twenty normal axis vertebra specimens were collected, comprising 18 adults, one 1-year-old child, and one 3-year-old child. Micro-CT, a high-resolution X-ray imaging technique, was used to scan and reconstruct three-dimensional models of these bones. In adult odontoid processes, three regions of interest were defined according to the Anderson-D' Alonzo classification: Region I, Region II, and Region III. Each region was evaluated for bone volume fraction, trabecular thickness, trabecular separation, trabecular number, Euler number, and structural model index. Group comparisons were conducted using one-way ANOVA. Results Micro-CT analysis revealed distinct developmental changes in odontoid processes structure, with patterns that may help explain fracture susceptibility. In pediatric specimens, a thick cortical bone layer surrounded the ossification center, resulting in a honeycomb-like trabecular pattern. In adults, only Region III retained trabecular lacunae, or small spaces among the bone struts. Quantitative analysis indicated that Region I had a higher bone volume fraction (0.62 ± 0.19) than Region II (0.47 ± 0.11) and Region III (0.40 ± 0.12) ( <italic>P</italic> < 0.05). Region III exhibited the greatest trabecular separation (0.68 ± 0.16) and the lowest connectivity (-1380.33 ± 906.28), reflecting reduced bone mass and internal support. Region II values were intermediate. Structurally, Region I displayed regular, lamellar trabeculae; Region II showed a transition to a reticular arrangement; and Region III contained sparse trabeculae surrounding empty spaces. Conclusions These structural findings indicate significant variation in the trabecular architecture of the odontoid process, shaped by developmental processes and mechanical demands. Region I is densely structured and robust, while Regions II and III contain more open, less dense bone and are mechanically weaker. These results provide a structural basis for the Anderson-D' Alonzo fracture classification and offer anatomical insights relevant to fracture etiology, bone health assessment, and individualized treatment strategies. </p>