ECTS Abstracts (2015) 1 P16

HR-pQCT and DXA changes in bone density and microarchitecture over two years in young adults

David A Hanley1, Lauren A Burt2, Sarah L Manske2, Jennifer L Bhatla2 & Steven K Boyd2

1CaMos Centre Director, Departments of Medicine, Community Health Sciences, and Oncology, University of Calgary, Calgary, Canada; 2McCaig Institute for Bone and Joint Health, Department of Radiology, Faculty of Medicine, University of Calgary, Calgary, Canada.

Timing of peak bone microarchitecture parameters measured with high-resolution peripheral quantitative computed tomography (HR-pQCT) may differ from dual x-ray absorptiometry (DXA) due to resolution or skeletal site differences. We aimed to assess differences in timing of peak values for microarchitecture and bone density using HR-pQCT and DXA. Females (n=42, 21.5 yrs) and males (n=33, 21.6 yrs) from the Calgary youth cohort of the Canadian Multicentre Osteoporosis Study (CaMos) participated in a 2-year follow-up study. DXA (Hologic, USA) scans of the left hip provided areal bone mineral density (aBMD) of femoral neck (FN) and total hip (TH). Non-dominant radius and left tibia were scanned using HR-pQCT (Scanco Medical, Switzerland). To compare repeat scans, automated 3D image registration was conducted (IPL software). Total volumetric BMD (Tt.BMD), cortical BMD (Ct.BMD), trabecular BMD (Tb.BMD) and cortical porosity (Ct.Po) were assessed. Repeated measures ANOVA determined age-related bone change. DXA-derived aBMD decreased at the hip for females and males by 0.5-1.0% per year (p<0.01). At the radius, volumetric BMD increased by 0.6-1.0% per year for males and females (p<0.01). There were no significant changes in Ct.Po at the radius (p>0.05). At the tibia, there were no significant changes in volumetric BMD; however, Ct.Po increased 7% for females and 10% per year for males (p<0.01). Our findings are consistent with known DXA peaks occurring before 20 years at the hip. An increase in HR-pQCT-derived BMD parameters at the radius, suggests peak density at the radius occurs at an age >22 years. At the tibia, all HR-pQCT-derived BMD parameters remained stable, suggesting peak density may occur before 22 years. Like DXA, timing of peak HR-pQCT values differ according to skeletal site (radius vs. tibia). Cohorts used for HR-pQCT normative data should include recruitment of subjects <22 years of age to capture peak measurements for all sites.

Disclosure: The authors declared no competing interests. This work was supported by CIHR (MOP-106611).

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