Prediction of Incidental Osteoporotic Fractures at Vertebral-Specific Level Using 3D Non-Linear Finite Element Parameters Derived from Routine Abdominal MDCT

Abstract

To investigate whether finite element (FE) analysis of the spine in routine thoracic/abdominal multi-detector computed tomography (MDCT) can predict incidental osteoporotic fractures at vertebral-specific level; Baseline routine thoracic/abdominal MDCT scans of 16 subjects (8(m), mean age: 66.1 ± 8.2 years and 8(f), mean age: 64.3 ± 9.5 years) who sustained incidental osteoporotic vertebral fractures as confirmed in follow-up MDCTs were included in the current study. Thoracic and lumbar vertebrae (T5-L5) were automatically segmented, and bone mineral density (BMD), finite element (FE)-based failure-load, and failure-displacement were determined. These values of individual vertebrae were normalized globally (g), by dividing the absolute value with the average of L1-3 and locally by dividing the absolute value with the average of T5-12 and L1-5 for thoracic and lumbar vertebrae, respectively. Mean-BMD of L1-3 was determined as reference. Receiver operating characteristics (ROC) and area under the curve (AUC) were calculated for different normalized FE (Kload, Kdisplacement,K(load)g, and K(displacement)g) and BMD (KBMD, and K(BMD)g) ratio parameter combinations for identifying incidental fractures. Kload, K(load)g, KBMD, and K(BMD)g showed significantly higher discriminative power compared to standard mean BMD of L1-3 (BMDStandard) (AUC = 0.67 for Kload; 0.64 for K(load)g; 0.64 for KBMD; 0.61 for K(BMD)g vs. 0.54 for BMDStandard). The combination of Kload, Kdisplacement, and KBMD increased the AUC further up to 0.77 (p < 0.001). The combination of FE with BMD measurements derived from routine thoracic/abdominal MDCT allowed an improved prediction of incidental fractures at vertebral-specific level.

MDCT-Based Finite Element Analysis for the Prediction of Functional Spine Unit Strength—An In Vitro Study

“…For modeling and anchoring of the ligaments, the half top and bottom vertebrae were not sufficient, so using the instances and translate option, the top and bottom vertebrae were created based on the middle vertebrae. As the mechanical properties of the adjacent vertebrae are not significantly different, we assumed it would not affect the results to a greater extent [ 21 , 27 ]. The translation distance between the vertebrae was determined by the distance between the vertebrae from MDCT images in the 3D slicer.…”

“…For calculating the failure load, compression loading condition was simulated by fixing the inferior surface of the bottom vertebrae, and normal displacement load was applied on the superior surface of the top vertebrae. The peak of the load–displacement curve was considered as the failure load [ 21 , 22 , 38 , 39 ].…”

“…FE method has been used for analyzing the vertebral bodies [ 17 , 18 , 19 , 20 ]. Studies have shown that FE-predicted failure loads have a higher correlation with the experimental loads and perform better than BMD-based measures in identifying patients at the risk of having bone fracture [ 17 , 21 ]. However, the spine is a complex biomechanical structure, with multiple interacting and connecting tissues.…”

Editorial on Special Issue “Spine Imaging: Novel Image Acquisition Techniques and Analysis Tools”

“…Other articles in this Special Issue have set a focus on the opportunistic use of MDCT data for osteoporosis diagnostics or prediction of incidental osteoporotic VFs (i.e., use of existing imaging data originally acquired for other purposes than osteoporosis screening, such as oncologic staging in cancer patients) [ 19 , 20 , 21 ]. In detail, Burian et al studied the contribution of bone mineral density (BMD) at different vertebral levels, subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) regarding the identification of VFs using baseline and follow-up image data from a 64-row MDCT scanner in patients (osteoporotic incidental VFs) and controls (no VFs) [ 20 ].…”

“…Furthermore, finite element analysis (FEA) as an advanced image analysis technique can be applied to MDCT data, which can relate morphological and material variations and properties to functional characteristics, thus providing 3D models of bone reconstructed from image data for the investigation of material properties within an FEA-meshed model [ 2 ]. In a study by Yeung et al, baseline routine MDCT scans (64-row MDCT scanner) of patients who sustained incidental osteoporotic VFs as confirmed in follow-up imaging were used for automated segmentation of thoracic and lumbar vertebrae (T5-L5), followed by BMD extraction and calculation of the FEA-based failure load and failure displacement [ 19 ]. The measurements of single vertebral bodies were normalized by dividing the absolute value by the average of L1–L3, as well as by dividing the absolute value by the average of T5–T12 and L1–L5, respectively [ 19 ].…”