Background: Patients with chronic kidney disease (CKD) have fracture rates above the general population and higher post-fracture mortality, yet bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) is less predictive of fractures in this population. HR-pQCT scans indicate a reduction in cortical thickness and increased cortical porosity in patients on dialysis, but it has limited accessibility and high expense. Cortical assessment of the hip using DXA has not been performed in this population.
Aim: To assess cortical parameters using BMD and advanced hip analysis (Lunar iDXA) in dialysis patients awaiting transplantation.
Methods: Normal ranges were first determined from 4,298 femur scans of women (mean age 72±7 years) and men (mean age 73±7 years) enrolled in the Dubbo Osteoporosis Epidemiology Study (DOES), and then compared with 65 women (age 46±13 years) and 90 men (age 49±13 years) receiving dialysis.
Results: Compared with older patients from DOES, women receiving dialysis had T-scores of -1.52±1.33 vs. -1.27±1.11 (non-significant), but significantly lower mean cortical thickness at the femoral neck (FN) of 2.53 ± 1.52 mm vs. 5.13±1.79 (p<0.001), and calcar of 3.26±1.20 mm vs. 3.82±1.2 (p<0.001). Buckling ratios (higher values indicate FN instability) were 8.01±4.57 vs. 3.97±1.68 (p<0.001). Men receiving dialysis had lower T-scores (-1.38±1.3 vs. -0.49±1.17, p<0.001), FN cortical width 2.91±1.98 mm vs. 5.84±2.32 (p<0.001) and calcar: 3.67±1.0 mm vs. 4.43±1.92 (p<0.001) compared with DOES men. Buckling ratios were 8.43±6.32 vs. 3.94±1.67 (p<0.001). Differences at the femoral shaft were non-significant in both men and women.
Conclusion: Stage 5D CKD has a profoundly adverse effect on cortical bone structure and strength. Cortical parameters measured non-invasively by DXA are markedly reduced in patients with CKD, even when compared to significantly older men and women, and should be assessed prospectively for utility in fracture prediction in this population.