Changes in Calcaneal Trabecular Bone Structure Assessed with High-Resolution MR Imaging in Patients with Kidney Transplantation

Abstract

The purpose of this study was to use high-resolution magnetic resonance (HR-MR) imaging to analyze the trabecular bone structure of the calcaneus in patients before and after renal transplantation and to compare this technique with bone mineral density (BMD) in predicting therapy-induced bone loss and osteoporotic fracture status. HR-MR imaging (voxel size: 0.195 x 0.195 x 1 mm) was performed at 1.5 T with an axial and sagittal orientation in 48 patients after transplantation, 12 patients before renal transplantation and 20 healthy controls. Structure measures analogous to standard histomorphometry and fractal dimension were determined in these images. BMD measurements of the lumbar spine and the proximal femur were obtained in the healthy female controls and the patients. Vertebral and peripheral fracture status were determined in all patients. The structural measures app.BV/TV, Tb.Sp, Tb.Th and Tb.N showed significant differences between controls and patients (p<0.05) while fractal dimension showed no significant differences. Neither the structural measures nor BMD showed significant differences between patients before and after transplantation. Correlations between time after transplantation versus structural measures and BMD were not significant. Differences between fracture and nonfracture patients were significant for the structural measures app.BV/TV, Tb.Sp and Tb.N (axial images) as well as for app.Tb.Th (sagittal images) and spine BMD (p<0.05) but not for hip BMD. Using odds ratios the strongest discriminators between patients with and without fractures were app. BV/TV, app.Tb.Sp (axial images) and app.Tb.Th (sagittal images), even after adjustment for age and BMD. Using receiver operating characteristic analysis the highest diagnostic performance was found for a combination of BMD and structural measures. In conclusion, our results indicate that structural measures obtained from HR-MR images may be used to characterize fracture incidence in kidney transplant patients; the best results, however, are obtained using a combination of BMD and structural measures.

A structural approach to the assessment of fracture risk in children and adolescents with chronic kidney disease

“…Grotz et al reported that vertebral deformities were associated with lower trabecular area, lower trabecular diameter, and increased intertrabecular spacing in transplant recipients compared with transplant recipients without vertebral deformities [66]. Link et al reported that transplant recipients had significantly lower MRI measures of BV/TV, Tb.Sp, Tb.Th, and Tb.N compared with controls; [67] however, spine QCT, trabecular BMD, and DXA hip and spine BMD did not differ between transplant recipients and controls. The MRI and QCT measures differed between fracture and nonfracture end-stage renal disease (ESRD) patients; DXA measures did not.…”

“…BV/TV did not differ significantly in this small sample of hemodialysis patients compared with controls; however, the pattern of lower surface and greater curve voxels suggested deterioration of the trabecular network. Two cross-sectional studies used high-resolution CT [66] or MRI [67] to evaluate trabecular architecture in renal transplant recipients; patients were evaluated months to years after transplantation. Grotz et al reported that vertebral deformities were associated with lower trabecular area, lower trabecular diameter, and increased intertrabecular spacing in transplant recipients compared with transplant recipients without vertebral deformities [66].…”

Finite Element Analysis Applied to 3-T MR Imaging of Proximal Femur Microarchitecture: Lower Bone Strength in Patients with Fragility Fractures Compared with Control Subjects

“…HR-pQ CT and high-spatial-resolution MR imaging have allowed noninvasive study of the microstructural determinants of fracture risk in vivo (21)(22)(23). However, HR-pQ CT and high-spatial-resolution MR imaging have been performed only in the distal extremities (14,15,22,24,25) and not in the hip, which is one of the most important fracture sites and a standard BMD assessment site. This is because HR-pQ CT scanners have small imaging bores that can fit only the ankle or wrist and because signal-to-noise ratio limitations arise when MR imaging of deeper anatomy such as the hip is performed.…”

Micro–MR Imaging–based Computational Biomechanics Demonstrates Reduction in Cortical and Trabecular Bone Strength after Renal Transplantation

“…Since micro-MR imaging does not involve ionizing radiation, it is particularly suited for repeated shortterm evaluation of bone disease in the immediate post-transplantation period. In a cross-sectional study, Link et al (18) reported significant differences in structural measures of trabecular bone in renal transplant recipients and of the calcaneus in control subjects.…”