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Summary: This study showed that regional bone blood flow and F-fluoride bone plasma clearance measured by positron emission tomography are three times lower at the hip than the lumbar spine. Introduction: Measurements of effective bone plasma flow ( K), bone plasma clearance ( K) and standardised uptake values (SUV) using F-fluoride positron emission tomography (F-PET) provide a useful means of studying regional bone metabolism at different sites in the skeleton. This study compares the regional F-fluoride kinetics and SUV at the hip and lumbar spine (LS). Methods: Twelve healthy postmenopausal women with no history of metabolic bone disease apart from two with untreated osteoporosis were recruited. Each subject underwent 60-min dynamic F-PET scans at the LS and proximal femur two weeks apart. K, K and SUV were measured at the LS (mean of L-L), femoral neck (FN), total hip (TH) and femoral shaft (FS). Differences between sites were assessed using the nonparametric Kruskal-Wallis test with a Bonferroni correction for multiple comparisons. Results: Values of K, K and SUV at the FN, TH and FS were three times lower than at the LS ( p = 0.003). Amongst the proximal femur sites, K and SUV were lower at the FS compared with the FN and TH, and SUV was lower at the TH compared with the FN (all p < 0.05). The volume of distribution was lower at the TH and FS compared with the LS ( p < 0.05). Conclusion: The lower values of K, K and SUV at the hip suggest that lower bone blood flow in the proximal femur is an important factor explaining the principal reason for the differences in bone fluoride kinetics between the LS and hip sites. [ABSTRACT FROM AUTHOR]

Summary: High bone mineral density on routine dual energy X-ray absorptiometry (DXA) may indicate an underlying skeletal dysplasia. Two hundred fifty-eight individuals with unexplained high bone mass (HBM), 236 relatives (41% with HBM) and 58 spouses were studied. Cases could not float, had mandible enlargement, extra bone, broad frames, larger shoe sizes and increased body mass index (BMI). HBM cases may harbour an underlying genetic disorder., Introduction: High bone mineral density is a sporadic incidental finding on routine DXA scanning of apparently asymptomatic individuals. Such individuals may have an underlying skeletal dysplasia, as seen in LRP5 mutations. We aimed to characterize unexplained HBM and determine the potential for an underlying skeletal dysplasia., Methods: Two hundred fifty-eight individuals with unexplained HBM (defined as L1 Z-score ≥ +3.2 plus total hip Z-score ≥ +1.2, or total hip Z-score ≥ +3.2) were recruited from 15 UK centres, by screening 335,115 DXA scans. Unexplained HBM affected 0.181% of DXA scans. Next 236 relatives were recruited of whom 94 (41%) had HBM (defined as L1 Z-score + total hip Z-score ≥ +3.2). Fifty-eight spouses were also recruited together with the unaffected relatives as controls. Phenotypes of cases and controls, obtained from clinical assessment, were compared using random-effects linear and logistic regression models, clustered by family, adjusted for confounders, including age and sex., Results: Individuals with unexplained HBM had an excess of sinking when swimming (7.11 [3.65, 13.84], p < 0.001; adjusted odds ratio with 95% confidence interval shown), mandible enlargement (4.16 [2.34, 7.39], p < 0.001), extra bone at tendon/ligament insertions (2.07 [1.13, 3.78], p = 0.018) and broad frame (3.55 [2.12, 5.95], p < 0.001). HBM cases also had a larger shoe size (mean difference 0.4 [0.1, 0.7] UK sizes, p = 0.009) and increased BMI (mean difference 2.2 [1.3, 3.1] kg/m(2), p < 0.001)., Conclusion: Individuals with unexplained HBM have an excess of clinical characteristics associated with skeletal dysplasia and their relatives are commonly affected, suggesting many may harbour an underlying genetic disorder affecting bone mass.