Patient-specific finite element modeling for femoral bone augmentation

Abstract

The aim of this study was to provide a fast and accurate finite element (FE) modeling scheme for predicting bone stiffness and strength suitable for use within the framework of a computer-assisted osteoporotic femoral bone augmentation surgery system. The key parts of the system, i.e. preoperative planning and intraoperative assessment of the augmentation, demand the finite element model to be solved and analyzed rapidly. Available CT scans and mechanical testing results from nine pairs of osteoporotic femur bones, with one specimen from each pair augmented by polymethylmethacrylate (PMMA) bone cement, were used to create FE models and compare the results with experiments. Correlation values of R2 = 0.72–0.95 were observed between the experiments and FEA results which, combined with the fast model convergence (~3 min for ~250,000 degrees of freedom), makes the presented modeling approach a promising candidate for the intended application of preoperative planning and intraoperative assessment of bone augmentation surgery.

Subject-specific planning of femoroplasty: A combined evolutionary optimization and particle diffusion model approach

“…The main purpose and contribution of this study is to introduce a patient-specific planning of femoral augmentation using validated individual simulation components (Basafa et al, 2013a; Basafa et al, 2013b). As part of ongoing research, the same femora are used for the augmentation experiments based on the proposed planning approach, and the results are compared to the simulations.…”

“…The advantages are no need for gradient calculation, ease of implementation, as well as less sensitivity to the discontinuities in the solution space. We used the CT volumes obtained from the specimens to create FE models, according to the procedure described earlier (Basafa et al, 2013a). Briefly, models consisted of layers of elements, each made of concentric rings of quadratic 20-node brick elements, completed with 15-node wedge elements at the center (Dhondt, 2004).…”

“…The augmented models were allowed to evolve until their predicted yield load for each specimen reduced to twice as high as its own non-augmented value. Yield load, at the end of each iteration, was predicted by assuming linearity for the resulting strains and scaling the force up until 1% volume of the bone elements reached the yield maximum or minimum principal strain (−0.0427 for compression (minimum) and 0.0299 for tension (maximum) (Basafa et al, 2013a)). The volume of the cement and the list of the cemented elements were recorded throughout the simulations.…”

“…In our previous studies we have developed a computational model for finite element (FE) analysis of femoral strength and the effect of femoroplasty on it (Basafa et al, 2013a), as well as a diffusion model for predicting the cement diffusion pattern inside porous trabecular bone using CT scan data (Basafa et al, 2013b). In this paper we propose a new paradigm for planning of femoroplasty using a combination of those previously validated numerical techniques.…”

Comparison of proximal femur and vertebral body strength improvements in the FREEDOM trial using an alternative finite element methodology

“…Moreover, FEA may not only estimate the risk of fracture but may also reveal the location and mechanism of fracture for a given load case [15][16][17][18][19]. Finally, FEA may be used to understand specific clinical conditions such as the presence of an implant [20,21], metastatic defects [22][23][24], cement augmentation [25,26], or remodeling over a certain loading regime [27]. In support of its steadily growing recognition, FEA was included in several evaluations of osteoporosis treatments [28][29][30][31][32][33][34][35] and of the deleterious effect of spaceflight on bone strength [36].…”