Longitudinal HR-pQCT and Image Registration Detects Endocortical Bone Loss in Kidney Transplantation Patients

Abstract

Patients with chronic kidney disease (CKD) who undergo kidney transplantation experience bone loss and increased risk of fracture. However, the mechanisms of this bone loss are unclear. Our objective was to use image registration to define the cortex to assess changes in cortical porosity (Ct.Po) in patients undergoing first-time kidney transplantation. We obtained serial measurements of parathyroid hormone (PTH) and bone turnover markers and used high-resolution peripheral quantitative computed tomography (HRpQCT) to scan the distal radius and tibia in 31 patients (21 men, 10 women; aged 51.9 AE 13.4 years) at transplant and after 1 year. Baseline and 1-year images were aligned using a fully automated, intensity-based image registration framework. We compared three methods to define the cortical region of interest (ROI) and quantify the changes: 1) cortical bone was independently defined in baseline and follow-up scans; 2) cortical bone was defined as the common cortical ROI; and 3) the cortical ROI at baseline was carried forward to 1-year follow-up (baseline-indexed). By the independently defined ROI, Ct.Po increased 11.7% at the radius and 9.1% at the tibia, whereas by the common ROI, Ct.Po increased 14.6% at the radius and 9.1% at the tibia. By the baseline-indexed ROI, which provides insight into changes at the endocortical region, Ct.Po increased 63.4% at the radius and 17.6% at the tibia. We found significant relationships between changes in Ct.Po and bone formation and resorption markers at the radius. The strongest associations were found between markers and Ct.Po using the baseline-index method. We conclude that Ct.Po increases throughout the cortex after kidney transplant, and this increase is particularly marked at the endocortical surface. These methods may prove useful for all HR-pQCT longitudinal studies, particularly when changes are expected at the endocortical region.

Deterioration of Cortical Bone Microarchitecture: Critical Component of Renal Osteodystrophy Evaluation

“…This study supports recent histomorphometric [25, 26, 37, 38] and imaging studies [16, 17, 27, 39, 40] that have reported changes in cortical bone microarchitecture in individuals with CKD. In a cross-sectional study involving 38 dialysis patients, Adragao et al [25] reported high cortical porosity in 57% and reported a significant inverse relationship between femoral bone mineral density and cortical porosity.…”

“…However, relatively few studies have endeavoured to use histomorphometry [25, 26] or micro-CT of bone trephine samples, or utilised non-invasive techniques [16, 17, 27] to assess cortical microarchitecture and porosity in patients with CKD G5, 5D or after kidney transplantation. In the current study, 50% of patients had changes consistent with high bone turnover on histomorphometry, accompanied by elevated PTH values, but all participants had markedly abnormal cortical microarchitecture assessed by micro-CT with relatively preserved trabecular structural parameters.…”

“…However, the assessment of cortical microarchitecture is described as an adjunct to the trabecular bone measurements. The common findings of cortical thinning and increased cortical porosity in recent studies of patients with CKD [16, 17] and their potential contribution to bone fragility suggest a need to emphasize the evaluation of cortical microarchitecture as a key parameter in addition to trabecular changes within the TMV classification.…”

Kidney transplantation and bone disease: risk factors of development and diagnostics

“…По сравнению с двухфотонной рентгеновской абсорбциометрией значительно более информатив ным методом исследования скелета (микроархи тектуры кости, раздельного определения объемной плотности кортикальной и трабекулярной областей, количественной оценки минеральной костной мас сы), но пока не получившего широкого внедрения в реальную клиническую практику, является пери ферическая количественная компьютерная томогра фия с высоким разрешением [53].…”

Application of quantitative computed tomography for assessment of trabecular bone mineral density, microarchitecture and mechanical property

“…Based on the result deduced from this study, it may be reasonable to suggest using the same time interval, and the same CACs image to monitor both osteoporosis and atherosclerosis in the general population. The high resolution pQCT (HR-pQCT) is primarily installed at major research centers and clinical radiology departments [111][112][113][114]. Using the high spatial resolution image (100 μm or less in pixel size), the resolution obtained is close to or smaller than the average trabecular thickness (100-150 μm) [12].…”