Predicting Hip Fracture Type With Cortical Bone Mapping (CBM) in the Osteoporotic Fractures in Men (MrOS) Study

Abstract

Hip fracture risk is known to be related to material properties of the proximal femur, but fracture prediction studies adding richer quantitative computed tomography (QCT) measures to dual‐energy X‐ray (DXA)‐based methods have shown limited improvement. Fracture types have distinct relationships to predictors, but few studies have subdivided fracture into types, because this necessitates regional measurements and more fracture cases. This work makes use of cortical bone mapping (CBM) to accurately assess, with no prior anatomical presumptions, the distribution of properties related to fracture type. CBM uses QCT data to measure the cortical and trabecular properties, accurate even for thin cortices below the imaging resolution. The Osteoporotic Fractures in Men (MrOS) study is a predictive case‐cohort study of men over 65 years old: we analyze 99 fracture cases (44 trochanteric and 55 femoral neck) compared to a cohort of 308, randomly selected from 5994. To our knowledge, this is the largest QCT‐based predictive hip fracture study to date, and the first to incorporate CBM analysis into fracture prediction. We show that both cortical mass surface density and endocortical trabecular BMD are significantly different in fracture cases versus cohort, in regions appropriate to fracture type. We incorporate these regions into predictive models using Cox proportional hazards regression to estimate hazard ratios, and logistic regression to estimate area under the receiver operating characteristic curve (AUC). Adding CBM to DXA‐based BMD leads to a small but significant (p < 0.005) improvement in model prediction for any fracture, with AUC increasing from 0.78 to 0.79, assessed using leave‐one‐out cross‐validation. For specific fracture types, the improvement is more significant (p < 0.0001), with AUC increasing from 0.71 to 0.77 for trochanteric fractures and 0.76 to 0.82 for femoral neck fractures. In contrast, adding DXA‐based BMD to a CBM‐based predictive model does not result in any significant improvement. © 2015 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Experimental validation of DXA-based finite element models for prediction of femoral strength

“…Quantitative computed tomography (QCT) can provide 3D distribution of volumetric BMD (vBMD) that can be measured in different femoral compartments (cortical, trabecular, total) [5,6]. However, this evaluation cannot be done routinely due to the high radiation dose on the patient.…”

Three-dimensional adiabatic inversion recovery prepared ultrashort echo time cones (3D IR-UTE-Cones) imaging of cortical bone in the hip

“…Using the 3D IR-UTE-Cones technique, cortical bone may be visualized with high contrast and T 2 ⁎ may be quantified, providing a single method to measure thickness and estimate porosity, respectively. Cortical bone thickness and porosity are both considered key elements for fracture risk [12,[15][16][17][18]. Specifically, cortical bone thinning and increasing porosity are important features for fracture initiation and propagation [15,16].…”

“…In vivo evaluation of cortical bone microstructure has been of great interest in both the orthopedic and radiologic communities [12,15,16]. Many research teams have attempted to quantify bone microstructure and assess the predictive value of various measures in determining fracture risk [17,18].…”

Focal osteoporosis defects play a key role in hip fracture

“…1) [19] but from a surgical perspective are managed differently. Even though the overall prediction of hip fractures using CBM and DXA was similar [20], identifying focal osteoporosis through imaging techniques such as CBM might help in the proactive prevention of hip fracture given that targeted implantation of locally acting pharmaceuticals via the greater trochanter is technically feasible [21]. Traditional QCT measures of femoral neck and ‘total hip’ areal Bone Mineral Density (for example CTXA™, Mindways Austin, Texas, USA [22]) are now in routine clinical usage for hip fracture prediction by incorporation in the WHO FRAX™ tool.…”