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Structural Determinants of Vertebral Fracture Risk
Author(s) -
Melton L Joseph,
Riggs B Lawrence,
Keaveny Tony M,
Achenbach Sara J,
Hoffmann Paul F,
Camp Jon J,
Rouleau Peggy A,
Bouxsein Mary L,
Amin Shreyasee,
Atkinson Elizabeth J,
Robb Richard A,
Khosla Sundeep
Publication year - 2007
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.070728
Subject(s) - medicine , quantitative computed tomography , bone density , bone mineral , osteoporosis , risk factor , lumbar vertebrae , fracture (geology) , logistic regression , vertebra , lumbar , orthodontics , surgery , materials science , composite material
Vertebral fractures are more strongly associated with specific bone density, structure, and strength parameters than with areal BMD, but all of these variables are correlated. Introduction: It is unclear whether the association of areal BMD (aBMD) with vertebral fracture risk depends on bone density per se, bone macro‐ or microstructure, overall bone strength, or spine load/bone strength ratios. Materials and Methods: From an age‐stratified sample of Rochester, MN, women, we identified 40 with a clinically diagnosed vertebral fracture (confirmed semiquantitatively) caused by moderate trauma (cases; mean age, 78.6 ± 9.0 yr) and compared them with 40 controls with no osteoporotic fracture (mean age, 70.9 ± 6.8 yr). Lumbar spine volumetric BMD (vBMD) and geometry were assessed by central QCT, whereas microstructure was evaluated by high‐resolution pQCT at the ultradistal radius. Vertebral failure load (∼strength) was estimated from voxel‐based finite element models, and the factor‐of‐risk (ϕ) was determined as the ratio of applied spine loads to failure load. Results: Spine loading (axial compressive force on L 3 ) was similar in vertebral fracture cases and controls (e.g., for 90° forward flexion, 2639 versus 2706 N; age‐adjusted p = 0.173). However, fracture cases had inferior values for most bone density and structure variables. Bone strength measures were also reduced, and the factor‐of‐risk was 35–37% greater (worse) among women with a vertebral fracture. By age‐adjusted logistic regression, relative risks for the strongest fracture predictor in each of the five main variable categories were bone density (total lumbar spine vBMD: OR per SD change, 2.2; 95% CI, 1.1–4.3), bone geometry (vertebral apparent cortical thickness: OR, 2.1; 95% CI, 1.1–4.1), bone microstructure (none significant); bone strength (“cortical” [outer 2 mm] compressive strength: OR, 2.5; 95% CI, 1.3–4.8), and factor‐of‐risk (ϕ for 90° forward flexion/overall vertebral compressive strength: OR, 3.2; 95% CI, 1.4–7.5). These variables were correlated with spine aBMD (partial r , −0.32 to 0.75), but each was a stronger predictor of fracture in the logistic regression analyses. Conclusions: The association of aBMD with vertebral fracture risk is explained by its correlation with more specific bone density, structure, and strength parameters. These may allow deeper insights into fracture pathogenesis.