Increased Cortical Porosity and Reduced Trabecular Density Are Not Necessarily Synonymous With Bone Loss and Microstructural Deterioration

Abstract

Absolute values of cortical porosity and trabecular density are used to estimate fracture risk, but these values are the net result of their growth‐related assembly and age‐related deterioration. Because bone loss affects both cortical and trabecular bone, we hypothesized that a surrogate measure of bone fragility should capture the age‐related deterioration of both traits, and should do so independently of their peak values. Accordingly, we developed a structural fragility score (SFS), which quantifies the increment in distal radial cortical porosity and decrement in trabecular density relative to their premenopausal mean values in 99 postmenopausal women with forearm fractures and 105 controls using HR‐pQCT. We expressed the results as odds ratios (ORs; 95% CI). Cortical porosity was associated with fractures in the presence of deteriorated trabecular density (OR 2.30; 95% CI, 1.30 to 4.05; p = 0.004), but not if trabecular deterioration was absent (OR 0.96; 95% CI, 0.50 to 1.86; p = 0.91). Likewise, trabecular density was associated with fractures in the presence of high cortical porosity (OR 3.35; 95% CI, 1.85 to 6.07; p < 0.0001), but not in its absence (OR 1.60; 95% CI, 0.78 to 3.28; p = 0.20). The SFS, which captures coexisting cortical and trabecular deterioration, was associated with fractures (OR 4.52; 95% CI, 2.17 to 9.45; p < 0.0001). BMD was associated with fracture before accounting for the SFS (OR 5.79; 95% CI, 1.24 to 27.1; p = 0.026), not after (OR 4.38; 95% CI, 0.48 to 39.9; p = 0.19). The SFS was associated with fracture before (OR 4.67; 95% CI, 2.21 to 9.88) and after (OR 3.94; 95% CI, 1.80 to 8.6) accounting for BMD (both p s < 0.0001). The disease of bone fragility is captured by cortical and trabecular deterioration: A measurement of coexisting cortical and trabecular deterioration is likely to identify women at risk for fracture more robustly than absolute values of cortical porosity, trabecular density, or BMD. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research

Post-fracture Risk Assessment: Target the Centrally Sited Fractures First! A Substudy of NoFRACT

“…A thinner cortex and increased cortical porosity at the proximal femur were associated with increased risk of fractures . The importance of coexisting cortical and trabecular deterioration for fracture propensity has recently been demonstrated using CT at distal forearm in women . Lower femoral neck BMD, lower TBS, and more prevalent vertebral fractures on VFA express lower total bone strength, which in this study is associated with serious fractures like hip and vertebral fractures, fractures that previously have been shown to be associated with increased morbidity and mortality …”

“…(23) The importance of coexisting cortical and trabecular deterioration for fracture propensity has recently been demonstrated using CT at distal forearm in women. (24,25) Lower femoral neck BMD, lower TBS, and more prevalent vertebral fractures on VFA express lower total bone strength, which in this study is associated with serious fractures like hip and vertebral fractures, fractures that previously have been shown to be associated with increased morbidity and mortality. (26)(27)(28)(29) Prospective studies have shown that low BMD measured at central, (17) as well as peripheral sites, (30,31) predicts any type of fracture.…”

Deterioration of Cortical and Trabecular Microstructure Identifies Women With Osteopenia or Normal Bone Mineral Density at Imminent and Long-Term Risk for Fragility Fracture: A Prospective Study

“…Cross‐sectional studies demonstrate that a measurement of microstructural deterioration distinguishes women with osteopenia and prevalent fractures from women with osteopenia without fractures . Recent prospective studies support the notion that microstructural deterioration identifies women with osteopenia having incident fractures …”

The Importance and Possible Clinical Impact of Measuring Trabecular and Cortical Bone Microstructure to Improve Fracture Risk Prediction

“…In this edition of the JBMR , Chapurlat and colleagues present a study in which they have investigated the association between incidence of fracture and a structural fragility score (SFS) derived from HRpQCT distal forearm measurements . The SFS score was developed by relating cortical porosity and trabecular density of the distal radius in postmenopausal women with radius fracture to reference values for these parameters in premenopausal women without fractures . HRpQCT assessments provide much more detail, including microstructural and geometric properties, than DXA does.…”

“…For example, measuring BMD at the hip provides the most accurate estimate for hip fracture prediction, indicating that site specificity is an important factor to consider. In the study by Chapurlat and colleagues, the SFS score used was originally derived from a cross‐sectional cohort of women with and without radius fracture . The SFS score then proved to be superior to DXA BMD of the femoral neck and FRAX in predicting fractures in two French cohorts of postmenopausal women (OFELY and QUALYOR) with mean ages of included women from 66 to 68 years.…”