Original Full Length ArticleCortical bone finite element models in the estimation of experimentally measured failure loads in the proximal femur
Highlights
► Sixty-one femurs were simulated using FE models including only cortical bone to estimate fracture loads. ► Experimentally measured failure load can be estimated with reasonable accuracy using the CT-based cortical bone FE model. ► The model is more predictive for fracture load than DXA and only slightly less accurate than a full bone model. ► The accuracy and calculation time of the model is promising for clinical use.
Introduction
Sideways falls are an important cause of hip fracture [1], [2]. Dual X-ray absorptiometry (DXA) is the standard diagnostic tool in the assessment of hip fracture risk, but it is insufficient to accurately predict who will and who will not encounter a fracture [3], [4]. Therefore, improvements in the prediction of bone strength, as a major risk factor of hip fracture, are needed. Particularly, studies on the failure mechanism of hip fracture in the sideways fall loading configuration [5] might offer improved tools for individual fracture risk assessment and focused preventative actions.
Finite element (FE) analysis is a valuable method for studying the hip fracture mechanics. Previously, FE analysis has been established as a noninvasive tool to estimate fracture load [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] using computed tomography (CT) imaging. The method has also been applied for the assessment of the risk for a specific fracture type, i.e. a femoral neck or trochanteric hip fracture [6], [20], [21], [22], [23]. In our previous study, we generated a CT-based FE model of femur using nonlinear analysis with a large sample size for a sideways fall configuration [24] and showed a high accuracy in the estimation of experimental fracture load (r2 = 0.87). Even though this kind of detailed model can offer high accuracy in failure load estimation, these models are complicated, require high computational power, and are time consuming, typically taking several hours per specimen. Thus, more effective solutions for clinical applications have to be developed and validated.
Cortical bone appears to be a key determinant of femoral strength [25], whereas trabecular bone is suggested to function mainly to reinforce the cortical bone [26]. The objective of this experimental FE study was to assess the predictive value of a simulation model including only cortical bone obtained from multi-detector (MD-) CT images in the estimation of experimentally measured fracture load of the proximal femur in a sideways loading configuration. The predictive value was compared with that of DXA, and with that of the previously presented full FE model [24].
Section snippets
Study sample
Sixty-one formalin-fixed cadaver femora (from 41 women and 20 men, age 55–100 years) [27], [28] were scanned with an MD-CT scanner (Sensation 16; Siemens Medical Solutions, Erlangen, Germany). The femora were mechanically tested for failure in a sideways fall loading configuration, as previously described [27]. FE analysis was performed to estimate the experimental fracture loads. Twenty-one of these femora (16 female and 5 male) were used for training, and 40 femora (25 female and 15 male) were
Results
The estimated fracture load values were highly correlated with the experimental ones (r2 = 0.73, standard error of the estimate SEE = 558 N, p < 0.001) (Fig. 1). The slope was 1.128 (not significantly different from 1, p = 0.253), with an intercept of − 360 N (not significantly different from 0, p = 0.362). The coefficient of determination was r2 = 0.68 for females and r2 = 0.70 for males (Table 1). The corresponding coefficients of determination between BMD and BMC, and the experimental fracture load were r2 =
Discussion
In this experimental FE study, a cortical bone simulation model that estimates the fracture load of formalin-fixed proximal femora was created. Based on the results, the proximal femoral failure load in a sideways fall configuration can be estimated with reasonable accuracy by using the CT-based bi-linear elastoplastic FE model including only cortical bone. The cortical model appeared to be more predictive for fracture load than DXA based BMD or BMC. Moreover, this simplified model of the
Acknowledgments
The authors acknowledge CSC‐IT Center for Science Ltd. for providing software and computational assistance. The study was supported by the Finnish Funding Agency for Technology and Innovation (grant no. 40463/05), the Academy of Finland, a grant from the Deutsche Forschungsgemeinschaft (DFG LO 730/3-1: Principal Investigator Dr. Eva-Maria Lochmüller), the National Doctoral Programme of Musculoskeletal Disorders and Biomaterials, the International Doctoral Programme of Biomedical Engineering and
References (31)
- et al.
Fracture incidence and association with bone mineral density in elderly men and women: the Rotterdam Study
Bone
(2004) - et al.
Prediction of the strength and fracture location of the femoral neck by CT-based finite-element method: a preliminary study on patients with hip fracture
J Orthop Sci
(2004) - et al.
Prediction of strength and strain of the proximal femur by a CT-based finite element method
J Biomech
(2007) - et al.
Prediction of proximal femur strength using a CT-based nonlinear finite element method: differences in predicted fracture load and site with changing load and boundary conditions
Bone
(2009) - et al.
Femoral strength is better predicted by finite element models than QCT and DXA
J Biomech
(1999) - et al.
Prediction of mechanical properties of cortical bone by quantitative computed tomography
Med Eng Phys
(2008) Improved prediction of proximal femoral fracture load using nonlinear finite element models
Med Eng Phys
(2001)- et al.
Comparison of in situ and in vitro CT scan-based finite element model predictions of proximal femoral fracture load
Med Eng Phys
(2003) - et al.
Prediction of femoral fracture load using finite element models: an examination of stress- and strain-based failure theories
J Biomech
(2000) - et al.
Load distribution in the healthy and osteoporotic human proximal femur during a fall to the side
Bone
(2008)
Prediction of fracture location in the proximal femur using finite element models
Med Eng Phys
Ct-based finite element models can be used to estimate experimentally measured failure loads in the proximal femur
Bone
During sideways falls proximal femur fractures initiate in the superolateral cortex: Evidence from high-speed video of simulated fractures
J Biomech
Contribution of trabecular and cortical components to the mechanical properties of bone and their regulating parameters
Bone
Spontaneous hip fractures, 44/872 in a prospective study
Acta Orthop Scand
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