QCT-based finite element prediction of pathologic fractures in proximal femora with metastatic lesions

Abstract

Predicting pathologic fractures in femora with metastatic lesions remains a clinical challenge. Currently used guidelines are inaccurate, especially to predict non-impeding fractures. This study evaluated the ability of a nonlinear quantitative computed tomography (QCT)-based homogenized voxel finite element (hvFE) model to predict patient-specific pathologic fractures. The hvFE model was generated highly automated from QCT images of human femora. The femora were previously loaded in a one-legged stance setup in order to assess stiffness, failure load, and fracture location. One femur of each pair was tested in its intact state, while the contralateral femur included a simulated lesion on either the superolateral- or the inferomedial femoral neck. The hvFE model predictions of the stiffness (0.47 < R 2 < 0.94), failure load (0.77 < R 2 < 0.98), and exact fracture location (68%) were in good agreement with the experimental data. However, the model underestimated the failure load by a factor of two. The hvFE models predicted significant differences in stiffness and failure load for femora with superolateral- and inferomedial lesions. In contrast, standard clinical guidelines predicted identical fracture risk for both lesion sites. This study showed that the subject-specific QCT-based hvFE model could predict the effect of metastatic lesions on the biomechanical behaviour of the proximal femur with moderate computational time and high level of automation and could support treatment strategy in patients with metastatic bone disease.

Effect of CT imaging on the accuracy of the finite element modelling in bone

“…Another important advantage is the availability of relatively fast and easy image-based model generation approaches. Such models have been used to predict bone strength [1][2][3], evaluate osteosynthesis- [4] and soft-tissue implants [5], investigate the effect of metastatic lesions on the bone's biomechanical behaviour [6,7] and many other subjects. Extensive research has been conducted to estimate the accuracy of FEM predicted bone behaviour.…”

“…Sample preparation parameters like presence and amount of soft tissue, presence of other limbs or anatomical structures within the FOV, presence and location of a phantom and scanner settings are some major examples. The vast majority of published FE models of bone are based on human specimens scanned in vitro with soft tissue removed for easier handling or instrumentation [2,4,6]. CT scanning of isolated bone specimens does not only facilitate the image segmentation but also eliminates additional sources of error that are due to increased noise, streak artefacts, and beam hardening caused by the presence of other skeletal elements, implants or large amounts of soft tissue within the FOV.…”

Post-operative fracture risk assessment following tumor curettage in the distal femur: a hybrid in vitro and in silico biomechanical approach

“…assess the bone strength. Thus, finite element analysis (FEA) based on quantitative computed tomography (QCT) images can be a powerful tool for predicting fracture risk 17 . This technique provides an accurate determination of material properties, based on a volumetric measurement of bone density, and considers effective mechanical factors on bone strength 17 .…”

“…Thus, finite element analysis (FEA) based on quantitative computed tomography (QCT) images can be a powerful tool for predicting fracture risk 17 . This technique provides an accurate determination of material properties, based on a volumetric measurement of bone density, and considers effective mechanical factors on bone strength 17 . Previous studies using the QCT-based FEA approach have reported promising results in predicting the strength of proximal femur 16 and vertebrae 15 .…”

“…In the past few years, biomechanical approaches using FEA or rigidity analyses have been employed to improve the accuracy in predicting fracture risk in patients with a bone tumour and to decide on the most appropriate reconstruction method following tumour curettage 5,11,12,[17][18][19] . Li et al utilized a patient-specific linear QCT-based FEA method to compare the stiffness and stress distribution in a distal femur with a bone defect (which was left empty) with the femora filled with bone cement and augmented with an internal fixation device following GCT curettage 18 .…”