Microvascular anatomy and mapping of intraosseous arterioles in the human L1 vertebral body: a histological study, literature comparison, and relevance for fracture healing.

Background: Post-traumatic vertebral necrosis is a challenging and unpredictable complication in spinal trauma, believed to result from ischemic injury due to vascular damage at the time of fracture, though this remains unproven. This study aims to provide a detailed anatomical description of the arterial microvasculature of the human L1 vertebral body, based on sequential histological analysis. Methods: Three L1 vertebrae were obtained from fresh adult human cadavers. The vertebral bodies were sequentially sectioned in the axial plane, from the upper to the lower endplates, and stained using hematoxylin-eosin, Masson's trichrome, and CD31 immunohistochemistry. Intraosseous vessels were analyzed using an automated algorithm for endothelial nuclei detection, combined with manual assessment of the location, orientation, and morphometric characteristics of arterial vessels. Results: A final set of 406 histological slides, corresponding to 406 vertebral body quadrants and comprising a total of 1,218 analyzed areas, was included in the study. Within the intraosseous compartment, the only arterial vessels identified were arterioles, totaling 13,712. Among these, third-order arterioles (lumen diameter 15-30 µm) were the most prevalent (42.31%), followed by second-order subtype B arterioles (lumen diameter 30-50 µm) (24.86%) and precapillary arterioles (lumen diameter 10-15 µm) (17.44%). A marked predominance of arterioles was observed in the anterior region (AR)-particularly within the anterior left quadrant (ALQ)-as well as in the peripheral area (PA) and central area (CA), with the highest prevalences located in the superior and middle vertical thirds of the vertebral body. In contrast, lower arteriole numbers were observed in the posterior region (PR), the intermediate area (IA), and the lower third of the vertebral body. Although obliquely oriented arterioles were more frequently observed across all regions, a significantly higher number of vertically oriented arterioles was identified in the CA. Conclusions: A detailed histological mapping of the intraosseous arterial microvasculature of the L1 vertebral body is presented and successfully integrated with existing three-dimensional anatomical descriptions, thereby enhancing the microvascular detail of previous models. A deeper understanding of this anatomical knowledge may serve as a foundation for incorporating the biological component of intraosseous arterial injury into the therapeutic algorithm for vertebral body fractures-particularly by improving the ability to predict whether a fracture will progress toward bone healing or evolve into non-union and post-traumatic necrosis.