Three-dimensional mapping of cortical porosity and thickness along the superolateral femoral neck in older women.

Although several studies have analyzed inter-individual differences in the femoral neck cortical microstructure, intra-individual variations have not been comprehensively evaluated. By using microCT, we mapped cortical pore volume fraction (Ct.Po) and thickness (Ct.Th) along the superolateral femoral neck in 14 older women (age: 77.1 ± 9.8 years) to identify subregions and segments with high porosity and/or low thickness-potential "critical" spots where a fracture could start. We showed that Ct.Po and Ct.Th significantly differed between basicervical, midcervical, and subcapital subregions of the femoral neck (p < 0.001), where the subcapital subregion showed the lowest mean Ct.Th and the highest mean Ct.Po. These cortical parameters also varied substantially with age and with the location of the analyzed microsegments along the individual's neck (p < 0.001), showing multiple microsegments with high porosity and/or low thickness. Although the highest ratio of these microsegments was found in the subcapital subregion, they were also present at other examined subregions, which may provide an anatomical basis for explaining the fracture initiation at various sites of the superolateral neck. Given that fractures likely start at structurally and mechanically weaker spots, intra-individual variability in Ct.Po and Ct.Th should be considered and the average values for the entire femoral neck should be interpreted with caution.