Microvasculature and trabecular bone in beagle proximal femur: Microstructural insights

Background: Avascular necrosis of femoral head and malunion are frequent post-operative complications of femoral neck fractures. To optimize surgical techniques, this study aims to provide a microstructural understanding of intraosseous microvasculature and the trabecular bone of the femoral head and neck.

Study design: This anatomical study analyzed twenty-eight femora from fourteen cadaveric beagles. Common iliac arteries were infused with colored silicone-resin for vascular visualization, followed by non-decalcified hard tissue processing using the EXAKT®, and Masson's trichrome staining. Morphology and histomorphometric analysis were performed by Nikon NIS Elements BR and ImageJ-fiji.

Results: Histomorphometry revealed thin, elongated trabeculae with high vascularity aligned parallel in the neck; numerous intraosseous anastomoses at the neck-shaft and head-neck junctions; thick trabeculae with smaller marrow cavities, and dense branching vascular networks near the cortex in the head. Quantitative analysis showed an inverse correlation between trabecular density and mean vascular density/vascular length density, with no significant sex or side differences. Dense connective tissue fibers maintained the microvasculature and trabeculae structure.

Conclusion: The femoral neck displayed an outside-in microvascular pattern via retinacular branches. Conversely, the femoral head had an inside-out pattern through epiphyseal branches reinforced by medullary branches. Dense intraosseous microvasculature aligned sub-cortically. The study identified a potential anatomical safe zone for screwing in femoral neck fractures in beagles. These findings provide an anatomical basis for translational research in joint preservation techniques for humans.