Adaptation of Proximal Femur to Mechanical Loading in Young Adults: Standard Vs Localized Regions Evaluated by DXA

Regions of the proximal femur with less adaptive protection by mechanical loading may be at increased risk of structural failure. Since the size and location of these regions diverge from those defined by the dual-energy X-ray absorptiometry manufacturers the purpose of this study was to compare areal bone mineral density (aBMD) of different regions of the proximal femur considering impact loads from physical activity (PA). The participants were 134 young adults divided into 2 groups according to the impact of PA performed in the last 12 mo: high-impact PA and low-impact PA. The aBMD of the proximal femur was assessed by dual-energy X-ray absorptiometry at the standard femoral neck, intertrochanter, and trochanter, and at specific locations of the superolateral femoral neck and intertrochanteric region. The bone-specific physical activity questionnaire was used to estimate the impact load of PA. Comparisons between groups were adjusted for body height and body lean mass. Interaction analysis between sex and PA groups were conducted with analysis of variance. Comparisons of aBMD between bone regions were analyzed separately for men and women with repeated measures analysis of variance. In the high-impact PA group, men benefit more than women at all bone regions, except the aBMD at intertrochanteric region. Analyses of repeated measures did not reveal any significant interaction effect between bone regions (standard vs specific) and PA groups (low vs high-impact). In conclusion, aBMD differences due to mechanical loading were more pronounced in men than in women; the magnitude of the aBMD differences as a result of different levels of PA was similar between standard and localized regions