3D characterization of pores in the cortical bone of human femur in the elderly at different locations as determined by synchrotron micro-computed tomography images

Abstract

Diaphysis, inferior, and lateral superior regions of the femoral neck are subjected to diverse mechanical loads. Using micro-CT based on synchrotron radiation, three-dimensional morphology and connectivity of the pore network are location dependent, underlying different remodeling mechanisms. The three-dimensional (3D) morphology and connectivity of the pore network at various locations in human femurs subjected to diverse mechanical loads were assessed using micro-CT based on synchrotron radiation. The cortex from 20 human femurs (mean age, 78.3 ± 12.4 years) was taken from the diaphysis (D), the inferior (IN), and the lateral superior (LS) regions of the femoral neck. The voxel size of the 3D reconstructed image was 7.5 μm. Cortical thickness and pore volume/tissue volume (Po.V/TV), pore diameter (Po.Dm) and spacing (Po.Sp) were determined. The pore surface/pore volume ratio (Po.S/Po.V), the number of pores (Po.N), the degrees of anisotropy (DA), and the connectivity density (ConnD), the degree of mineralization (DMB) were also determined. The characteristics of the pore network in femoral cortical bone were found to be location dependent. There was greater porosity, Po.Dm, and Po.N, and more large (180-270 μm), extra-large (270-360 μm) and giant pores (>360 μm) in the LS compared to the IN and D. The difference in porosity in between the periosteal and endosteal layers was mostly due to an increase of Po.Dm rather than Po.N. There was a lower DMB of bone in the LS, which is consistent with a higher remodeling rate. The results provide evidence for large variations in the structure of the internal pore network in cortical bone. These variations could involve different underlying remodeling mechanisms.