Spatial Differences in the Distribution of Bone Between Femoral Neck and Trochanteric Fractures

Abstract

There is little knowledge about the spatial distribution differences in volumetric bone mineral density and cortical bone structure at the proximal femur between femoral neck fractures and trochanteric fractures. In this case-control study, a total of 93 women with fragility hip fractures, 72 with femoral neck fractures (mean±SD age: 70.6±12.7 years) and 21 with trochanteric fractures (75.6±9.3 years), and 50 control subjects (63.7±7.0 years) were included for the comparisons. Differences in the spatial distributions of volumetric bone mineral density, cortical bone thickness, cortical volumetric bone mineral density and volumetric bone mineral density in a layer adjacent to the endosteal surface were investigated using voxel-based morphometry (VBM) and surface-based statistical parametric mapping (SPM). We compared these spatial distributions between controls and both types of fracture, and between the two types of fracture. Using VBM, we found spatially heterogeneous volumetric bone mineral density differences between control subjects and subjects with hip fracture, that varied by fracture type. Interestingly, femoral neck fracture subjects, but not subjects with trochanteric fracture, showed significantly lower volumetric bone mineral density in the superior aspect of the femoral neck compared to controls. Using surface-based SPM, we found that compared to controls both fracture types showed thinner cortices in regions in agreement with the type of fracture. Most outcomes of cortical and endocortical volumetric bone mineral density comparisons were consistent with VBM results. Our results suggest: 1) that the spatial distribution of trabecular volumetric bone mineral density might play a significant role in hip fracture; 2) that focal cortical bone thinning might be more relevant in femoral neck fractures; and 3) that areas of reduced cortical and endocortical volumetric bone mineral density might be more relevant for trochanteric fractures in Chinese women.

Heterogeneous Spatial and Strength Adaptation of the Proximal Femur to Physical Activity: A Within-Subject Controlled Cross-Sectional Study

“…In contrast, there was a lack of any appreciable tissue adaptation in the superior femoral neck region. This region is clinically relevant as: (1) it is exposed to greatest stress/strain during impact from a fall onto the greater trochanter; (2) femoral neck fractures appear to initiate in the region during a sideways fall; (3) the region experiences greater bone loss during aging compared with the more preserved inferior femoral neck; and (4) deficits in the region are associated with incident femoral neck fracture …”

“…We did observe improved bone properties at the greater trochanter with physical loading, likely due to muscle contractile forces, which may protect against greater trochanteric fractures. Deficits in the greater trochanter region have been associated with risk of greater trochanteric fracture …”

“…This region is clinically relevant as: (1) it is exposed to greatest stress/strain during impact from a fall onto the greater trochanter; (9)(10)(11)(12) (2) femoral neck fractures appear to initiate in the region during a sideways fall; (13,14) (3) the region experiences greater bone loss during aging compared with the more preserved inferior femoral neck; (24,43) and (4) deficits in the region are associated with incident femoral neck fracture. (26,34,44,45) The lack of adaptation at the superior femoral neck was coupled with an absence of side-to-side differences in proximal femur ultimate strength under loading from a fall onto the greater trochanter, the type of loading most associated with femoral neck fractures during aging. There were D-to-ND leg differences in pitchers in yield strength under fall loading, indicating an enhanced ability to resist plastic deformation and damage initiation.…”

“…SPM was used to assess for localized D‐to‐ND leg differences in the spatial distribution of bone properties. In particular, voxel‐based morphometry was used for vBMD, and cortical bone mapping for cortical vBMD (Ct.vBMD), cortical thickness (Ct.Th), and vBMD in a layer adjacent to the endosteal surface (EndoTb.vBMD) . Proximal femur images from the nondominant leg were mirrored to those of the dominant leg, and the segmented bones spatially normalized to a minimum deformation template representing the average size and shape of all proximal femora in the study.…”

“…vBMD). (26) Proximal femur images from the nondominant leg were mirrored to those of the dominant leg, and the segmented bones spatially normalized to a minimum deformation template representing the average size and shape of all proximal femora in the study. The spatial normalizations reduced the anatomical variability among the femora, effectively establishing anatomical correspondences locally.…”