The assessment of the risk of fracture in femora with metastatic lesions

Abstract

Previously, we showed that case-specific non-linear finite element (FE) models are better at predicting the load to failure of metastatic femora than experienced clinicians. In this study we improved our FE modelling and increased the number of femora and characteristics of the lesions. We retested the robustness of the FE predictions and assessed why clinicians have difficulty in estimating the load to failure of metastatic femora. A total of 20 femora with and without artificial metastases were mechanically loaded until failure. These experiments were simulated using case-specific FE models. Six clinicians ranked the femora on load to failure and reported their ranking strategies. The experimental load to failure for intact and metastatic femora was well predicted by the FE models (R(2) = 0.90 and R(2) = 0.93, respectively). Ranking metastatic femora on load to failure was well performed by the FE models (τ = 0.87), but not by the clinicians (0.11 < τ < 0.42). Both the FE models and the clinicians allowed for the characteristics of the lesions, but only the FE models incorporated the initial bone strength, which is essential for accurately predicting the risk of fracture. Accurate prediction of the risk of fracture should be made possible for clinicians by further developing FE models.

Finite element analysis and CT-based structural rigidity analysis to assess failure load in bones with simulated lytic defects

“…For the validation of CTRA and FEA we relied on the exact results of mechanical experiments as performed previously [27, 28]. For an elaborate description of the setup of these experiments, the reader is referred to this previous work.…”

“…The mesh generation for the FE models was accomplished by segmenting the QCT images and converting them to a solid mesh (Patran 2005 r2, MSC Software Corporation, Santa Ana, CA, USA) [28]. Calibration of the QCT scans and material property assignment was performed using the DICOM Toolkit software package, developed at the Orthopaedic Research Lab in Nijmegen [28].…”

“…In the current study we aim to establish and assess statistical comparisons between QCT structural rigidity analyses and FE analyses, in their accuracy for the estimation of femoral failure load. For that purpose, we use an experimental dataset and the corresponding FE simulations as described previously [27, 28]. Based on these experiments, we performed a QCT structural rigidity analysis and compared these results to the results from the FE analyses.…”

Formation of microcracks near surgical defect in femur: Assessment of ultimate loading conditions

“…This approach is currently widely used for prediction of fractures and corresponding loads as well as localization of fracture in femur under different loading conditions; important results in this area are described in [1,2,9,10,13,14]. Assessments of fracture risk and definition of a failure load for bones with metastatic lesions based on the finite-element method were carried out in [3,5,7,15,16]. In a study on prediction of fracture load and objective assessment of the failure of femur with lytic defects [11], an engineering theory of beams was used in conjunction with tomographic data on structural stiffness.…”

“…In a study on prediction of fracture load and objective assessment of the failure of femur with lytic defects [11], an engineering theory of beams was used in conjunction with tomographic data on structural stiffness. Basically, FE modelling and corresponding experimental verification were carried out for femurs with metastatic lesions of round or oval shape [3,7,11,16]. FE simulations of femurs with rectangular-shaped defects were carried out in [5] and [15].…”