Three-Dimensional Microstructural Basis for Differential Occurrence of Subcapital versus Basicervical Hip Fractures in Men.

Abstract

We analyzed the bone microarchitecture of the subcapital and basicervical subregions of the femoral neck in men, to determine whether microarchitectural differences of cortical or trabecular bone can explain differential frequency of subcapital vs. basicervical fractures, especially in aged persons. The study sample encompassed twenty male proximal femora obtained during autopsy. They were divided in two age groups: young (< 40 years, n = 10) and aged (> 60 years, n = 10). Micro-computed tomography was used to evaluate cortical and trabecular microarchitecture of the subcapital and basicervical regions of the superolateral femoral neck-typical fracture initiation site. Basicervical region showed significantly thicker and less porous cortex than subcapital region (p = 0.02, p < 0.001, respectively), along with increased distance between cortical pores (p = 0.004) and smaller pore diameters (p = 0.069). Higher trabecular number (Tb.N: p = 0.042), lower trabecular thickness (Tb.Th: p < 0.001), and lower trabecular separation (p = 0.003) were also hallmarks of the basicervical compared to subcapital region, although BV/TV was similar in both regions (p = 0.133). Age-related deterioration was mostly visible in trabecular bone (for BV/TV, Tb.Th, Tb.N and fractal dimension: p = 0.026, p = 0.049, p = 0.059, p = 0.009, respectively). Moreover, there were tendencies to age-specific patterns of trabecular separation (more pronounced inter-site differences in aged) and cortical thickness (more pronounced inter-site differences in young). Trabecular microarchitecture corresponded to cortical characteristics of each region. Our study revealed the microarchitectural basis for higher incidence of subcapital than basicervical fractures of the femoral neck. This is essential for better understanding of the fracture risk, as well as for future strategies to prevent hip fractures and their complications.