Quantitative computed tomography-based finite element analysis predictions of femoral strength and stiffness depend on computed tomography settings

Abstract

The aim of the present study was to compare proximal femur strength and stiffness obtained experimentally with estimations from Finite Element Analysis (FEA) models derived from Quantitative Computed Tomography (QCT) scans acquired at two different scanner settings. QCT/FEA models could potentially aid in diagnosis and treatment of osteoporosis but several drawbacks still limit their predictive ability. One potential reason is that the models are still sensitive to scanner settings which could lead to changes in assigned material properties, thus limiting their results accuracy and clinical effectiveness. To find the mechanical properties we fracture tested 44 proximal femora in a sideways fall-on-the-hip configuration. Before testing, we CT scanned all femora twice, first at higher resolution scanner settings, and second at a lower resolution scanner settings and built 88 QCT/FEA models of femoral strength and stiffness. The femoral set neck bone mineral density, as measured by DXA, uniformly covered the range from osteoporotic to normal. This study showed that the femoral strength and stiffness values predicted from high and low resolution scans were significantly different (p < 0.0001). Strength estimated from high resolution QCT scans was larger for osteoporotic, but smaller for normal and osteopenic femora when compared to low resolution scans. In addition, stiffness estimated from high resolution scans was consistently larger than stiffness obtained from low resolution scans over the entire femoral dataset. While QCT/FEA techniques hold promises for use in clinical settings we provided evidence that further improvements are required to increase robustness in their predictive power under different scanner settings and modeling assumptions.

The Effect of Quantitative Computed Tomography Acquisition Protocols on Bone Mineral Density Estimation

“…Although the study differentiated the predictive outcomes based on these two scanning protocols which combined voltage, current, and kernel, it did not consider the individual effects of these variables. The variations in measured HU values and estimated vBMD using phantoms could thus lead to incorrect estimations of bone strength and stiffness from FE models, as demonstrated in their study [21].…”

“…As this study demonstrates, the correlation between HU values and thereby estimated vBMD using a phantom will depend on the acquisition parameters. A previous study by Dragomir-Daescu et al showed predicted strength and stiffness of QCT/FEA models to differ between a high-and a lowresolution scanning protocol [21]. Although the study differentiated the predictive outcomes based on these two scanning protocols which combined voltage, current, and kernel, it did not consider the individual effects of these variables.…”

“…However, any variability arising from the QCT acquisition protocol may affect the material property assignment, resulting in an imprecise fracture risk prediction. Dragomir-Daescu et al demonstrated that QCT/ FEA predicted strength and stiffness vary between models developed from high-and low-resolution scans [21]. With more scientists utilizing QCT in fracture risk assessment and FE modeling in osteoporosis related research, the effect of several common scanning parameters and postprocessing settings on vBMD estimates should be further studied.…”

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking

“…Techniques such as quantitative computed tomography (QCT)-based FEA have gained popularity due to their ability to incorporate both bone morphology and bone mechanical material properties. However, existing QCT-based FEA of the lower extremities (such as the tibia and the knee) generally has, by and large, been limited to biomechanical changes due to age-or disease-related bone degeneration and often uses idealized or highly simplified loading conditions (i.e., it only includes a few muscle forces) [18]. In contrast, exercise-related activities, such as walking while carrying loads, induce dynamic (time-varying) muscular and joint forces on the tibia.…”

Quantitative Computed Tomography Protocols Affect Material Mapping and Quantitative Computed Tomography-Based Finite-Element Analysis Predicted Stiffness

“…A previous study has demonstrated that QCT/FEA predicted bone strength and stiffness can vary between models developed with high-resolution scans, used in the research community, and low-resolution scans, used in the clinical setting [12]. Furthermore, estimated volumetric bone mineral density (vBMD) values used for material properties' assignments in finite-element models measured from CT images were also shown to depend on scanning protocols [13].…”