In Vivo μMRI-Based Finite Element and Morphological Analyses of Tibial Trabecular Bone in Eugonadal and Hypogonadal Men Before and After Testosterone Treatment

Abstract

Osteoporosis is a major public health problem in men. Hypogonadal men have decreased BMD and deteriorated trabecular bone architecture compared with eugonadal men. Testosterone treatment improves their BMD and trabecular structure. We tested the hypothesis that testosterone replacement in hypogonadal men would also improve their bone's mechanical properties. Ten untreated severely hypogonadal and 10 eugonadal men were selected. The hypogonadal men were treated with a testosterone gel for 24 mo to maintain their serum testosterone concentrations within the normal range. Each subject was assessed before and after 6, 12, and 24 mo of testosterone treatment by MRI of the distal tibia. A subvolume of each MR image was converted to a microfinite element (FE) model, and six analyses were performed, representing three compression and three shear tests. The anisotropic stiffness tensor was calculated, from which the orthotropic elastic material constants were derived. Changes in microarchitecture were also quantified using newly developed individual trabeculae segmentation (ITS)-based and standard morphological analyses. The accuracy of these techniques was examined with simulated MR images. Significant differences in four estimated anisotropic elastic material constants and most morphological parameters were detected between the eugonadal and hypogonadal men. No significant change in estimated elastic moduli and morphological parameters was detected in the eugonadal group over 24 mo. After 24 mo of treatment, significant increases in estimated elastic moduli E 22 (9.0%), E 33 (5.1%), G 23 (7.2%), and G 12 (9.4%) of hypogonadal men were detected. These increases were accompanied by significant increases in trabecular plate thickness. These results suggest that 24 mo of testosterone treatment of hypogonadal men improves estimated elastic moduli of tibial trabecular bone by increased trabecular plate thickness.

Potential of in vivo MRI‐based nonlinear finite‐element analysis for the assessment of trabecular bone post‐yield properties

“…Some of the authors of the present work have previously shown that in vivo MRI-based μFE simulations in the linear regime predict the expected changes in the bone's mechanical behavior in response to drug intervention 11,12 or following renal transplantation. 18 The present work is the first on in vivo μMR image-based nonlinear μFE modeling.…”

“…[7][8][9] With advances in imaging techniques and computational methods, image-based micro-finite element analysis (μFEA) has become a valuable noninvasive tool for evaluating bone mechanical properties in response to external loads. [10][11][12] Linear-elastic μFE models are most often utilized to keep computational demands at a manageable level. Highresolution image-based linear μFE estimates, notably elastic moduli, have been shown to agree very well with measurements from mechanical compression tests.…”

“…Linear-elastic μFE models generated from μMR images have recently demonstrated their potential to monitor alterations in bone mechanical properties resulting from disease progression or drug intervention. 11,12,18 However, to the best of the authors' knowledge, there have been no reports on image-derived nonlinear μFEA based on in vivo μMRI data.…”

Impaired bone microarchitecture at the distal radius in older men with low muscle mass and grip strength: The STRAMBO study

“…(38,39) In men, low testosterone levels are associated with lower RASM and strength and poor trabecular microarchitecture. (4,40,41) Lower grip strength and lower Tb.vBMD were found in secondary hyperparathyroidism. (42,43) However, the trends we observed were significant after adjustment for physical activity, smoking, and hormonal levels.…”

Fractal lacunarity of trabecular bone and magnetic resonance imaging: New perspectives for osteoporotic fracture risk assessment

“…TBA analysis by using MRI has been demonstrated to be more sensitive than BMD even in monitoring several therapeutic effects: salmon calcitonin in different skeleton sites [46] testosterone at distal tibia [47] ; alendronate in peripheral districts [48] . By comparing CT and MRI [32,49] , CT has the advantage to visualize bone tissue with a higher space resolution while has the disadvantage to high doses of radiation when applied to central skeleton districts such as vertebras and femur neck, the two best sites to estimate fracture risk in primitive (postmenopausal and senile) osteoporosis.…”