Robust QCT/FEA Models of Proximal Femur Stiffness and Fracture Load During a Sideways Fall on the Hip

Abstract

Clinical implementation of quantitative computed tomography-based finite element analysis (QCT/FEA) of proximal femur stiffness and strength to assess the likelihood of proximal femur (hip) fractures requires a unified modeling procedure, consistency in predicting bone mechanical properties, and validation with realistic test data that represent typical hip fractures, specifically, a sideways fall on the hip. We, therefore, used two sets (n = 9, each) of cadaveric femora with bone densities varying from normal to osteoporotic to build, refine, and validate a new class of QCT/FEA models for hip fracture under loading conditions that simulate a sideways fall on the hip. Convergence requirements of finite element models of the first set of femora led to the creation of a new meshing strategy and a robust process to model proximal femur geometry and material properties from QCT images. We used a second set of femora to cross-validate the model parameters derived from the first set. Refined models were validated experimentally by fracturing femora using specially designed fixtures, load cells, and high speed video capture. CT image reconstructions of fractured femora were created to classify the fractures. The predicted stiffness (cross-validation R2 = 0.87), fracture load (cross-validation R2 = 0.85), and fracture patterns (83% agreement) correlated well with experimental data.

Nonlinear quasi-static finite element simulations predict in vitro strength of human proximal femora assessed in a dynamic sideways fall setup

“…The reason for the moderate predictions of the present study may be the relatively high portion of trochanteric fractures (71%), which appear to be in general more challenging to capture via FE. Another FE study reported good agreement for seven out of nine samples in the validation set (Dragomir-Daescu et al, 2011), while the distinction between "good" and "fair" matching was different than the one used here. In the recent study of Schileo et al location of failure onset was accurately predicted by the FE models for five out of six samples in fall loading mode (Schileo et al, 2014).…”

“…Numerous previous studies used finite element (FE) analysis to predict fracture properties of bones via virtual mechanical testing (Ariza et al, 2015;Cody et al, 1999;Dall'Ara et al, 2013a;Dragomir-Daescu et al, 2011;Keyak et al, 2001;Luisier et al, 2014). In order to avoid the above mentioned complexities related to the dynamic event, most FE models aim at predicting the quasi-static behavior of bones.…”

A quasi-brittle continuum damage finite element model of the human proximal femur based on element deletion

“…In general, at a low load rate (quasi-static regime), the proximal femur behaves as a quasi-brittle material with a non-linear behavior till complete fracture [6,19,[36][37]. In this case, quasi-brittle behavior laws are well suited to represent the non-linear behavior before complete fracture observed during quasi-static proximal fracture experiments.…”

An Automated Method to Estimate Femoral Shape and Mineral Mass

“…One of the possible applications of a triangular mesh was for finite element analysis (FEA), which computes and evaluates the mechanical properties of the femur [1]. The goal was to determine if the mesh built, using MC was also suitable for FEA.…”

“…Three papers by the Mayo Clinic's Division of Engineering [1]- [3] describe a technique to make three-dimensional (3D) models of the proximal femur geometry and mineral distribution using mostly manual and semi-automated methods. Their models were used for accurate finite element estimation of stiffness and load of the bone.…”