Bone mass and microarchitecture in CKD patients with fracture

Abstract

Patients with predialysis chronic kidney disease (CKD) have increased risk for fracture, but the structural mechanisms underlying this increased skeletal fragility are unknown. We measured areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry at the spine, hip, and radius, and we measured volumetric BMD (vBMD), geometry, and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the radius and tibia in patients with CKD: 32 with fracture and 59 without fracture. Patients with fracture had lower aBMD at the spine, total hip, femoral neck, and the ultradistal radius, the last having the strongest association with fracture. By HR-pQCT of the radius, patients with fracture had lower cortical area and thickness, total and trabecular vBMD, and trabecular number and greater trabecular separation and network heterogeneity. At the tibia, patients with fracture had significantly lower cortical area, thickness, and total and cortical density. Total vBMD at both radius and tibia most strongly associated with fracture. By receiver operator characteristic curve analysis, patients with longer duration of CKD had area under the curve of >0.75 for aBMD at both hip sites and the ultradistal radius, vBMD and geometry at the radius and tibia, and microarchitecture at the tibia. In summary, patients with predialysis CKD and fractures have lower aBMD by dual-energy x-ray absorptiometry and lower vBMD, thinner cortices, and trabecular loss by HR-pQCT. These density and structural differences may underlie the increased susceptibility to fracture among patients with CKD.

Figure 1.

Osteoporosis is significantly more common at the total hip and ultradistal radius in CKD patients with fracture. (*P < 0.05).

Figure 2.

HR-pQCT provides detailed images of bone geometry and microarchitecture at the radius (left) and tibia (right). (A) Scout view represents the reference line position (solid line) and the measurement site (dotted line). (B) Images from a healthy, postmenopausal white woman. (C) Images from a predialysis female patient with CKD and without fracture. (D) Images from a predialysis female patient with CKD and with prevalent fracture.

Figure 3.

Longer kidney disease duration associates with improved fracture discrimination by DXA and HR-pQCT. Tertile 1, ≤2.7 years; tertile 2, 2.7 to 6.9 years; tertile 3, ≥6.9 years; black, vertical line corresponds to AUC 0.75.