BMD measurement by DXA method in useful for estimation of bone strength of lumbar vertebra in CKD-MBD model rats

In patients with chronic renal failure, especially patients receiving continuous hemodialysis, the risk of fracture increases as Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) advances. In hemodialysis patients, bone fracture is a serious issue because it leads to decreased Activities of Daily Living (ADL) and associated increases in medical expenses and mortality risk. We usually measure Bone Mineral Density (BMD) in order to estimate the fracture risk, but there is no certain consensus as to which part of the bone should we measure. Also, the relationship between decreased BMD and lowered bone strength has not established yet. To resolve those issues, the femur and lumbar vertebra were harvested from renal failure rats with controlled Parathyroid Hormone (PTH) levels, and their BMD and bone strength were measured directly. There was significant positive correlation between the lumbar vertebra BMD and femur BMD (r = 0.51, P = 0.002). This result indicates that BMD in other areas could be estimated from any specific area. In all rats, the BMD reflected the lumbar vertebra bone strength independently of the area measured (r = 0.51, P = 0.0007 vs L2-4 BMD; r = 0.40, P = 0.018 vs femur BMD) but did not reflect the bone strength of the femur. The present study showed that the relationship between BMD and bone strength obviously existed in lumbar vertebra, the effect of bone metabolism was reflected earlier and BMD measurement using the Dual energy X-ray Absoptiometry (DXA) method was useful for determining lumbar bone strength.