QCT-based spatio-temporal aging atlas of the proximal femur BMD and cortical geometry

Aging is associated with an increased risk of fragility fractures at the hip, resulting from a loss of bone mass. While this loss is typically reported as a decreased mean areal bone mineral density (aBMD) in the proximal femur or the femoral neck, its evolution is spatially inhomogeneous, which might also contribute to the increased risk of fractures. Yet, little is known about the evolution of BMD distribution and cortical thickness with age in the proximal femur. We propose a 3D spatio-temporal atlas of the proximal femur to identify regions with high BMD losses and cortical thinning. The atlas is based on 532 post-mortem QCT scans from donors aged 20 to 94, including 179 female subjects. A point cloud with anatomically corresponding positions was defined for each femur based on a personalized coordinate system. The evolution of BMD and cortical thickness was computed as a multiple linear regression with age and BMI, for female and male subjects separately. The average BMD decrease with age was significant in all subregions for both sexes but higher in females. High BMD losses were observed in the superior and middle neck regions, in the medial part of the head, and in the trochanteric trabecular bone. BMD was well preserved in the inferior neck and, for males, in cortical regions. In both sexes, the cortical thickness decreased significantly in the superior and posterior neck cortex and increased significantly in the inferior neck. Higher BMI was associated with increased BMD in the inferior neck and medial shaft cortex, as well as with increased cortical thickness in all neck and shaft regions for both sexes. The spatio-temporal atlas showed the evolution of BMD distribution and cortical thickness in the proximal femur, with high losses in typical fracture locations, such as the femoral neck and pertrochanteric regions.