• Principal compressive trabeculae exhibit a functionally graded porous structure, with region 5 showing the highest bone volume fraction, trabecular thickness, and grayscale value.
• Principal tensile trabeculae show region 3 with the highest bone volume fraction, trabecular thickness, trabecular number, and grayscale value, while region 2 has the lowest.
• A reliable method for extracting the volume of interest of principal stress trabeculae was proposed, enabling detailed morphometric analysis.
• The findings provide new insights into the microstructural anatomy of principal stress trabeculae, potentially informing the design of novel bionic hip prostheses.