To determine if pQCT could identify HD patients with fractures, we conducted a cross-sectional study in 52 men and women on HD. We found that cortical, but not trabecular, pQCT measures were associated with fractures.Introduction: Fractures are common in hemodialysis (HD) patients, yet DXA is inconsistently associated with fractures. One explanation for this lack of association may be that HD patients have a selective decrease in cortical density not identified by standard DXA. Materials and Methods: We used pQCT to examine cross-sectional associations between cortical and trabecular measures and fractures in 36 men and 16 women, ജ50 years of age, on HD for at least 1 year. We confirmed low-trauma nonspine fractures since starting HD. Prevalent vertebral fractures were identified by morphometry of lateral spine X-rays. pQCT measurements of the nondominant radius included trabecular density, cortical density, total area, cortical area, and cortical thickness. We also obtained DXA measurements of the hip and lumbar spine. We used logistic regression models, adjusted for age, weight, and sex, to examine the association between fracture (vertebral and/or self-reported nonspine) and each pQCT measure. Results are reported as ORs per SD decrease in the independent variable. Results: The mean age was 65.8 ± 9.0 (SD) years, the mean weight was 72.3 ± 15.6 kg, most (32 of 52) subjects were white, and there were 32 fractures in 27 subjects (prevalent vertebral fracture or low-trauma fracture) since starting dialysis. A decrease in cortical density was associated with fractures (OR ‫ס‬ 16.67; 95% CI: 2.94-83.33), as was a decrease in cortical area (OR ‫ס‬ 3.04; 95% CI: 1.28-7.25) and a decrease in cortical thickness (OR ‫ס‬ 3.26; 95% CI: 1.36-7.87). Fractures were not associated with pQCT trabecular density (OR ‫ס‬ 1.18; 95% CI: 0.6-2.33), total area (OR ‫ס‬ 1.1; 95% CI: 0.59-1.7), or DXA measurements of the hip and spine. Conclusions: Cortical parameters of the radius were associated with fractures in HD patients. If confirmed in prospective studies, these findings may explain the lack of association between fracture and standard DXA measurements and raise the possibility that pQCT could be used to identify HD patients at high risk of fracture.

Summary The goal in this study was to determine the relationship between body mass index and trabecular and cortical bone using quantitative computed tomography. A higher body mass index (BMI) was positively associated with trabecular and cortical bone parameters, and serum parathyroid hormone, and negatively associated with cortical volumetric bone mineral density (vBMD) and serum 25-hydroxy-vitamin D. When BMI is greater than 35 kg/m2, adiposity affects vBMD and may explain the higher fracture risk in this population without low BMD. Introduction The influence of adult obesity on the trabecular and cortical bone, geometry, and strength has not been fully addressed. The goal in this study was to determine the relationship between body mass index and trabecular and cortical bone mass and geometry, over a wide range of body weights. Methods We examined 211 women (25–71 years; BMI 18–57 kg/m2) who were classified into three categories of BMI (kg/m2) including normal-weight (BMI<25), overweight and obese-class I (BMI 25–35) and obese-class II–III (BMI>35), and also by menopausal status. Volumetric bone mineral density (mg/cm3), trabecular, and cortical components as well as geometric characteristics at the 4%, 38%, and 66% from the distal tibia were measured by peripheral quantitative computed tomography, and serum was analyzed for parathyroid hormone (PTH) and 25-hydroxy-vitamin D (25OHD). Results Higher BMI was associated with greater values of trabecular bone and cortical BMC and area and PTH (r>0.39, p<0.001), but lower cortical vBMD and 25OHD (r>−0.27, p<0.001). When controlling for lower leg muscle area, fat area was inversely associated with cortical vBMD (r=−0.16, p<0.05). Premenopausal obese women with both higher BMI and PTH had lower cortical vBMD (r<−0.40, p<0.001). While age is a predictor for most bone variables, fat mass explains more variance for vBMD, and lean mass and 25OHD explain greater variance in geometric and strength indices (p<0.05). Conclusions Severe obesity (BMI>35) increases trabecular vBMD and in the presence of a higher PTH is associated with a lower cortical vBMD without compromising bone geometry and strength. Whether or not a lower cortical vBMD in obesity influences fracture risk over time needs to be further explored.

These findings underscore the independent associations of subcutaneous and intermuscular fat among men of African ancestry, an effect that may be modified by a family history of diabetes. Further studies are needed to identify the genetic and physiologic mechanisms that influence the distribution and remodeling of adipose tissue in skeletal muscle with aging.'

Many fractures occur in individuals without osteoporosis defined by areal bone mineral density (aBMD). Inclusion of other aspects of skeletal strength may be useful in identifying at-risk subjects. We used surrogate measures of bone strength at the radius and tibia measured by peripheral quantitative computed tomography (pQCT) to evaluate their relationships with nonvertebral fracture risk. Femoral neck (FN) aBMD, measured by dual-energy X-ray absorptiometry (DXA), also was included. The study population consisted of 1143 white men aged 69+ years with pQCT measures at the radius and tibia from the Minneapolis and Pittsburgh centers of the Osteoporotic Fractures in Men (MrOS) study. Principal-components analysis and Cox proportional-hazards modeling were used to identify 21 of 58 pQCT variables with a major contribution to nonvertebral incident fractures. After a mean 2.9 years of follow-up, 39 fractures occurred. Men without incident fractures had significantly greater bone mineral content, cross-sectional area, and indices of bone strength than those with fractures by pQCT. Every SD decrease in the 18 of 21 pQCT parameters was significantly associated with increased fracture risk (hazard ration ranged from 1.4 to 2.2) independent of age, study site, body mass index (BMI), and FN aBMD. Using area under the receiver operation characteristics curve (AUC), the combination of FN aBMD and three radius strength parameters individually increased fracture prediction over FN aBMD alone (AUC increased from 0.73 to 0.80). Peripheral bone strength measures are associated with fracture risk and may improve our ability to identify older men at high risk of fracture. © 2011 American Society for Bone and Mineral Research.