Use of DXA-based finite element analysis of the proximal femur in a longitudinal study of hip fracture

Abstract

Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA) is used for clinical assessment of fracture risk; however, measurements that incorporate bone strength could improve predictive ability. The aim of this study was to determine whether bone strength derived from finite element (FE) analysis was associated with hip fracture risk in a longitudinal study. We studied 728 women (mean age 82 years), 182 with subsequent hip fracture. FE models were generated from baseline DXA scans of the hip to determine femoral bone strength and load-to-strength ratio (LSR). The baseline LSR was significantly higher in fracture cases (median 1.1) compared with controls (0.7, p < 0.0001). Femoral strength and BMD were also significantly lower in cases (median 1820 N, 0.557 g/cm 2 ) compared with controls (2614 N, 0.618 g/cm 2 ) both p < 0. In conclusion, the DXA-based FE model was able to discriminate incident hip fracture cases from controls in this longitudinal study independently from FN BMD, prior fracture, VFA, and FRAX score. Such an approach may provide a useful tool for better assessment of bone strength to identify patients at high risk of hip fracture who may benefit from treatment to reduce fracture risk. ß

Study of sex differences in the association between hip fracture risk and body parameters by DXA-based biomechanical modeling

“…1(b)). Analysis was performed on the critical regions of interest (ROI) rather than the critical cross-sections, considering that a single-element failure does not indicate gross fracture of the whole bone [65]. This approach can also decrease the sensitivity of the results to the image processing algorithms [71].…”

“…assuming the plane-stress approach, i.e., considering that proximal femur is a plate with a constant thickness [65,66]. Then, isotropic inhomogeneous material properties were derived from vBMD using the empirical equations of Morgan and colleagues [67,68] …”

“…If FRI is greater than one, the patient is in a high risk of hip fracture. The femoral strength was then derived as the onset impact force that causes the FRI exceeding one [65,66]. This was calculated by scaling the impact force by the factor FRI as:…”

“…An image-processing algorithm, that combined edge detection and thresholding, was used to segment the proximal femur. A subject-specific thickness of the proximal femur was first derived as [65,66]:…”

Role of cortical bone in hip fracture

“…Cases also had thinner 34,35 bone cortices. But re-calculated 2D DXA estimates of bending resistance (reflected in Section Modulus) were somewhat 36 or little better than BMD in predicting hip fracture. 37,38 Computed 3D tomography studies combined with finite element analysis (FEA) are generally superior to 2D DXA for predicting strength.…”