Evaluating accuracy of structural geometry by DXA methods with an anthropometric proximal femur phantom

Differences in geometric strength at the contralateral hip between men with hip fracture and non-fractured comparators

Older men sustain excess bone mineral density (BMD) declines after hip fracture; however, BMD provides no information on mechanical structure and strength. The aim was to assess whether changes in hip bone geometry in older men after hip fracture differ than that expected with aging. Two cohorts were used: Baltimore Hip Studies 7th cohort (BHS-7) and Baltimore Men's Osteoporosis Study (MOST). The sample (N = 170) included older Caucasian men with hip fracture that were propensity score matched (1:1) to community-dwelling non-fractured comparators. Hip Structural Analysis (HSA) calculated aerial BMD and metrics of bone structural strength: cross-sectional bone area (CSA), cortical outer diameter (OD), section modulus (SM), and centroid position (CP). Mixed-effect models estimated changes in HSA parameters and adjusted robust regression models evaluated between-cohort differences in annual percent change at the narrow neck (NN), intertrochanteric (IT), and femoral shaft (FS). Hip fracture was associated with statistically greater declines in NN CSA (β = -2.818; 95% CI: -3.300%, -2.336%), SM (β = -1.896%; 95% CI: -2.711%, -1.080%) and CP (β = -0.884%; 95% CI: -0.889%, -0.880%) and significantly larger increases in NN OD (β = 0.187%; 95% CI: 0.185%, 0.190%). Differences in IT HSA parameters were like the NN but larger in magnitude, while there were favorable changes in FS geometry where fragility fractures are rare. Findings indicate there are declines in bone structure and strength at the NN and IT regions of the proximal femur in older men during hip fracture recovery that far exceed what occurs during normal aging.

Longitudinal changes in hip geometry in relation to the final menstrual period: Study of Women's Health Across the Nation (SWAN)

BACKGROUND

In SWAN, we showed that accelerated loss of bone mineral density (BMD) begins 1 year before the final menstrual period (FMP) to 2 years after the FMP and slows thereafter. However, the risk of fracture depends on both BMD and bone geometry. The hip structural analysis (HSA) measures important geometric properties of bone. Changes in HSA parameters across the menopausal transition have not been previously assessed.

METHODS

The current analysis uses data from SWAN, 5 years before to 5 years after FMP (N = 900, Age (mean(SD)) = 46.85(2.60), 44% White). HSA parameters at the femoral narrow neck were obtained from 2D DXA scans and normalized to baseline values. FMP was determined from annual interviews. Changes in HSA were assessed over 3 periods, 5 to 2 years before FMP (pre-transmenopausal), 2 years before to 1 years after FMP (transmenopausal), 1 to 5 years after FMP (postmenopausal). Mixed linear models with random slopes were used to estimate the rate of change in HSA parameters relative to FMP.

RESULTS

Loss of BMD, cross-sectional area (CSA), and section modulus (SM) and increases in outer diameter (OD) were greatest in the transmenopausal period (p for all<0.05). Changes continued in the postmenopausal period but were not statistically significant. The cumulative percentage changes over 10 years in BMD (-10.67%), CSA (-9.01), SM (-7.03) and OD (+1.95) were statistically significant.

CONCLUSION

Changes in hip geometry across the menopause transition parallel changes in BMD and provide insight into mechanisms that may increase risk of fragility fracture.