Protective effect of beta blockers in postmenopausal women: influence on fractures, bone density, micro and macroarchitecture.

INTRODUCTION: Animal studies suggest that bone remodeling is under beta-adrenergic control via the sympathetic nervous system. beta blockers have been suggested to stimulate bone formation and/or inhibit bone resorption in animals as well as to reduce the risk of fracture in humans. The purpose of this study was to examine if these agents can have a preventive or therapeutic effect in osteoporosis. MATERIALS AND METHODS: We have studied the association of beta blockers use with BMD, bone geometry, microarchitecture and fractures rates in postmenopausal women referred for bone density testing. From a total sample of 944 women, we identified 158 women who were taking beta blockers and 341 age-matched women as controls. Bone geometry was investigated at the femoral neck on DXA images. Microarchitecture was evaluated by the H mean fractal parameter at the calcaneus. RESULTS: The odds ratio for fracture (at all sites) in the beta blocker users was 0.56 (95% CI, 0.30-0.99). beta blocker use was associated with a higher BMD at the femoral neck (+4.2%, p<0.05) and L1-L4 (+3.2%, p<0.05). Proximal femur scans revealed significantly higher cortical width (+3.6%, p<0.05) at the femoral neck under beta blockers. Femoral shaft measurement did not significantly differ under beta blockers. Medication use and lifestyle factors indicated no association between beta blockers and smoking, alcohol use, physical activity, corticosteroids and estrogen therapies. The H mean parameter was significantly higher in the beta blockers group (0.619+/-0.029 vs. 0.607+/-0.023 in controls, p<0.05), suggesting a better trabecular microarchitectural organization. CONCLUSION: Our data suggest that the association of current use of beta blockers with low fracture risk is mediated, at least in part, by effects on BMD, cortical bone geometry and trabecular bone microarchitecture.

Fractal analysis of bone X-ray tomographic microscopy projections.

Fractal analysis of bone X-ray images has received much interest recently for the diagnosis of bone disease. In this paper, we propose a fractal analysis of bone X-ray tomographic microscopy (XTM) projections. The aim of the study is to establish whether or not there is a correlation between three-dimensional (3-D) trabecular changes and two-dimensional (2-D) fractal descriptors. Using a highly collimated beam, 3-D bone X-ray tomographic images were obtained. Trabecular bone loss was simulated using a mathematical morphology method. Then, 2-D projections were generated in each of the three orthogonal directions. Finally, the model of fractional Brownian motion (fBm) was used on bone XTM 2-D projections to characterize changes in bone structure that occur during disease, such a simulation of bone loss. Results indicate that fBm is a robust texture model allowing quantification of simulations of trabecular bone changes.

Bone texture analysis on direct digital radiographic images: precision study and relationship with bone mineral density at the os calcis.

Assessment of bone microarchitecture in complement to bone mineral density (BMD) exam could improve prediction of osteoporotic fractures. A high-resolution X-ray prototype was developed to assess microarchitecture quality. Images were obtained on os calcis; then, three texture parameters were calculated on the same region of interest (ROI): a fractal parameter, a run-length parameter, and a co-occurrence parameter. This work describes the reproducibility of this method. We also examine the relationship between texture parameters and BMD at a site-matched ROI. Measurements on the left heel were performed on 30 healthy women, on the same day, with repositioning for short-term precision error. An additional measurement was done at 1 week to evaluate mid-term precision error on 14 subjects. Os calcis images from 10 healthy women were used to evaluate both intra- and interobserver reproducibility. Thirty other healthy patients were measured successively on two similar devices for interprototype comparison. BMD and texture analyses of the left heel were obtained from 57 women. Short-term precision errors ranged 1.16-1.24% according to the texture parameter. Mid-term precision error was slightly higher than short-term precision for the mean Hurst exponent parameter. Comparisons of texture parameters and BMD at a site-matched ROI on the os calcis showed no significant relationships. The results also show that the use of this high-resolution digital X-ray device improves the reproducibility of parameter measurement compared to the indirect digitization of radiologic films previously used.

Subchondral bone micro-architectural alterations in osteoarthritis: a synchrotron micro-computed tomography study.

OBJECTIVES: We evaluated the three-dimensional (3D) micro-architecture of subchondral trabecular (Tb) bone in osteoarthritis (OA). Due to high signal-to-noise ratio and high resolution, micro-computed tomography (micro-CT) by synchrotron radiation is considered as the gold standard for bone micro-architecture imaging. DESIGN: Subchondral bone were extracted from femoral heads in OA cases in areas without cartilage (OAc-; n=6) and in adjacent areas with cartilage (OAc+; n=6) and compared to eight subchondral bone cores from osteoporosis cases (OP). The voxel size of images was 10.13 microm. We measured the bone volume fraction (BV/TV) and morphological parameters: Tb thickness (TbTh), Tb spacing (TbSp), Tb number (TbN), and bone surface/bone volume (BS/BV). The degree of anisotropy (DA), the connectivity by the Euler number and the degree of mineralization (DM) were equally assessed. RESULTS: BV/TV and morphological parameters showed significant differences between OAc- and OP samples (P<0.01 except TbTh: P<0.05) and between OAc- and OAc+ (0.05

Fractal analysis of bone texture: a screening tool for stress fracture risk?

BACKGROUND: The aim of this study was to identify specific bone characteristics of stress fracture (SF) cases in sportswomen. To date, no tool is able to distinguish individuals who are at risk, limiting preventive measures. MATERIAL AND METHODS: We investigated the skeletal system of sportswomen who did sustain SF in the past (n = 19) and compared it with that of female controls (C) with a similar sporting history but without any fracture history (n = 20). Bone mass and body composition were measured using dual-energy X-ray absorptiometry. Bone micro-architecture was investigated by calcaneal ultrasound and fractal analysis of calcaneus radiographic images. Oestradiol levels were measured by E.I.A, and IGF-1 by R.I.A. Menstrual characteristics, nutrient intake, and training were assessed using questionnaires. RESULTS: The result of the fractal analysis, expressed by the Hmean parameter, was significantly lower in the SF group, reflecting a more complex structure of the trabecular micro-architectural organization (P < 0.005). Body mass index (BMI) at birth was also found to be lower in the SF cases as compared with their C (P < 0.03). Multivariate analysis revealed that the fractal parameter Hmean, bone mineral content (BMC) at Ward's triangle and the BMI at birth correctly assigned 84.85% of the female athletes into their respective SF or C groups (P = 0.001). CONCLUSION: These results suggest that the fractal parameter and the BMI at birth may be able to identify female athletes most at risk for this overuse bone injury, as their low indexes might reflect a greater skeletal sensitivity.