Diagnostics, Berkeley, CA; David L. Kopperdahl, O.N. Diagnostics, Berkeley, CA;S. Orwoll, Oregon Health & Science University, Portland, OR

Finite element (FE) analysis of quantitative CT (QCT) scans provides an integra-tive measure of strength for the proximal femur and can be combined withestimates of the in vivo loads acting at the hip during a fall to calculate a load-to-strength ratio. We studied the relation of such biomechanical measures to therisk of incident hip fracture in men, alone and in combination with other fracturerisk factors. A case-cohort design was used to identify a randomly selected subco-hort of 225 men and 45 incident hip fracture cases from among 3549 communitydwelling men (age O65) followed on average for 5.5 years after a baseline hipQCT scan. FE analyses of the QCT scans were performed (n 5 250 total, 40with fractures), blinded to fracture status, to simulate a sideways fall and invivo loads were estimated from mass and height data. Cox proportional hazardsregression models were used to compute the hazard ratio (HR) per standard devi-ation (SD) change in FE outcome after controlling for age, study site, body massindex (BMI), and areal BMD (by DXA). The HR per SD change in FE-strength,load-to-strength ratio, and BMD were highly significant before and after adjustingfor age (Table). When additionally adjusted for BMD (and study site and BMI,which had little effect), the HR for the load-to-strength ratio remained statisticallysignificant. These results provide unique insight into hip fracture etiology anddemonstrate the clinical potential of such a biomechanical approach to the assess-ment of hip fracture risk.

Poster Number 193 Prevention and Treatmentof Osteoporosis

THE EFFECT OF INCLUDING QUS ASSESSMENT INFRACTURE RISK PREDICTION MODELS FOR OLDERMEN AND WOMEN: THE EPIC-NORFOLK COHORTSTUDY

Alireza Moayyeri, PhD student in Epidemiology, Department of PublicHealth and Primary Care

Stephan Kaptoge, Department of Public Health and Primary Care, University ofCambridge; Robert N Luben, Department of Public Health and Primary Care,University of Cambridge; Sheila Bingham, Department of Public Health andPrimary Care, University of Cambridge; Nicholas J Wareham, Jonathan Reeveand Kay-Tee Khaw

The role of quantitative ultrasound (QUS) in clinical practice is still debatable. Al-though QUS is correlated with BMD and bone structure, whether QUS predictsfractures independently of BMD is unclear. We examined this in a sample ofmen and women in the European Prospective Investigation into Cancer (EPIC)-Norfolk who had both heel QUS and hip DXA between 1995 and 1997 andwere followed for any incident fracture up to March 2007. From 1,454 participants(701 men) aged 65e76 years at baseline, 79 developed a fracture over 15,567 per-son-years of follow-up. In sex-stratified Cox proportional-hazard model includingage, total hip BMD, height, weight, history of fracture, smoking, and alcohol in-take, BMD was significantly associated with fracture risk (RR 5 0.44 per SD;95%CI 5 0.33e0.58). After inclusion of heel broadband ultrasound attenuation(BUA) into the model, both BMD (RR 5 0.52 per SD; 95%CI 5 0.39e0.70)and BUA (RR 5 0.64 per SD; 95%CI 5 0.48e0.86) had significant associationwith fractures. Global measures of model fit, area under ROC curve, andHosmer-Lemeshow statistic showed superiority of the model including BUA.We further calculated exact 10-year absolute fracture risk for all participantsand categorized them in groups of !5%, 5% to !15%, and e15%. Comparisonof groupings based on two Cox models showed a total reclassification of 12.7%of participants after inclusion of BUA with the greatest reclassification (24.1%)among the moderate risk group. This study shows that adding QUS to modelswith DXA measurements improves our predictive power and urges for further at-tention to QUS as a clinical tool for prevention of fractures.

Poster Number 194 Prevention and Treatmentof Osteoporosis

MICRO-STRUCTURAL BASIS OF BONE FRAGILITY INWOMEN AND MEN

Ali Ghasem-Zadeh, Honorary Research Fellow of EndocrinologyDepartment, University of Melbourne, Australia

Q. Wang, Honorary Research Fellow of Endocrinology Department, University ofMelbourne, Australia; Xf. Wang, PhD Student, Endocrinology Department,University of Melbourne, Australia; A.M. Evans, Senior Technologist of BoneDensitometry, Endocrinology Department of Melbourne University, Australia;S. Iuliano R. Zebazi and E. Seeman

Introduction: The morphological basis for the higher bone fragility in women thanmen is incompletely understood because of the limited study of three dimensionalstructure. We examined sex differences in morphology of the peripheral skeletonacross age using a high resolution peripheral quantitative computed tomography(HR-pQCT) to better define the sexual dimorphism in bone fragility and fractureincidence . Material and Methods: The distal radius and tibia were scanned at us-ing Xtreme CT scanner (Scanco Medical AG, Bassersdorf, Swiess) in 237 healthyCaucasians (178 females aged 22e98 years and 59 males aged 24e98 years). In-dependent t-test was used for comparison between sex and age groups. Short termreproducibility for vBMD and trabecular structures was 0.86e1.52% and 7e8%,respectively. Results: At both sites, males had higher peak total vBMD than fe-males, a difference that was sustained across life despite a decline in both sexes.Cortical thickness and vBMD decreased in both sexes but similarly so the differ-ence present in young adulthood were sustained. Decrease in trabecular numberwas observed after 35 years in females. Trabecular thickness decreased in malesso increased trabecular separation was found in females not males. Conclusion:Bone fragility increases in both sexes but sex differences at peak are important de-terminants of sex differences in old age. Males have larger bones making themmore resistant to bending, bone loss occurs by thinning rather than loss of connec-tivity, probably due to the sustained low remodelling rate in males, cortical thin-ning and porosity increases in both sexes but later in males and probably accountsfor the reduction in cortical vBMD. Higher fracture rates in females are the resultof more women having structural features in old age that make bone strength lessthan the loads imposed. Key words: HR-pQCT, Aging, Normal population, BMD.

Poster Number 195 Radiographic Absorptiometry

EFFICACY OF GH-TREATMENT ON BMD CHANGES INCHILDREN WITH GH-DEFICIENCY, FOLLOWED FOURYEARS BY DIGITAL X-RAY RADIOGRAMMETRYVGROWTH

Corina Galesanu, Professor of Endocrinology, University of Medicine andPharmacy, Iasi, Romania

Mihail Romeo Galesanu, Centre of Radiology and Imaging Diagnosos, Iasi,Romania

Growth hormone (GH) has an essential role in bone mass accumulation and reach-ing a normal peak bone mass. Digital X-ray Radiogrammetry (DXR-BMD) is anefficient clinical method of estimating BMD. We purposed to follow the BMD inchildren with isolated GHD under GH replacement therapy using DXR-BMD.Twenty-seven GHD children: 7 girls and 20 boys vs 10 normal children were eval-uated. The mean age at the initiation therapy was 8.4 years for girls and 10.7 yearsfor boys. No puberty on set when therapy was initiated. The treatment was foundin 0.03 mg/kg body weight/day Somatropin. For the girls, growth delay was SD:�3.0� 0.2, bone age retardation: �2.4� 0.4 years, mean GH level 1.32 mUI/ml, GH after insulin stimulation: 5.08 mUI/ml, IGF1 basal level: 70ng/ml. Afterthe treatment the mean height gain was 29.84 cm. The mean of bone mass accu-mulation determined DXR-BMD was 0.032� 0.2 g/cm2/year vs control group0.054� 0.8 g/cm2/year. Mean level of IGF1 was 685.5 mg/ml. For the boysgrowth delay was SD: �3.5� 0.2, bone age retardation: �3.2� 0.4 years, meanGH basal level 0.6 mUI/ml. GH after stimulation: 3.4 mUI/ml, mean level ofIGF1 67.02 ng/ml. After the treatment the mean level of IGF1 was 600.7 ng/ml,the height mean gain was 28.5 cm. The mean of bone mass accumulation was0.034� 0.2 g/cm2/year vs control group 0.047� 0.2 g/cm2/year. At two boyswith without treatment the DXR-BMD rested unmodified after one year. In our se-ries of children the bone mass increases significantly during rhGH-therapy. Thetreatment should be continued after the end of linear growth for attain peakbone mass during adulthood.

468 Abstracts

Journal of Clinical Densitometry: Assessment of Skeletal Health Volume 11, 2008