Assessment of trabecular and cortical parameters using high-resolution peripheral quantitative computed tomography, histomorphometry and microCT of iliac crest bone core in hemodialysis patients

Evaluation of Bone Biomarkers in Renal Osteodystrophy

Renal osteodystrophy (ROD) represents histological bone changes in patients with chronic kidney disease and is classified according to turnover and mineralization. This cross-sectional study evaluates several bone biomarkers and their ability to discriminate turnover and mineralization defects in hemodialysis (HD) patients. Bone-specific [BSAP] and total [tAP] alkaline phosphatase, procollagen-1 N-terminal propeptide [P1NP], C-terminal cross-linking telopeptide [CTX], intact [iPTH] and whole [wPTH] parathyroid hormone, sclerostin [SOST], fibroblast growth factor 23 [FGF-23], vitamin D, osteoprotegerin [OPG], and receptor activator of nuclear factor κB ligand [RANKL] were collected before the bone biopsy. Thirty-two patients were evaluated by bone histomorphometry, which identified mineralization defects and low and high turnover in 47%, 50%, and 41% of patients, respectively. Bone biomarkers (tAP, BSAP, CTX, P1NP) and hormones (iPTH, wPTH, and SOST) were capable of identifying low and high turnover (AUC > 0.877 and >0.857, respectively, p < 0.001). PTH plus AP had the best accuracy for identifying high turnover. BSAP > 2x, iPTH > 8x, and wPTH > 6x upper limit of normal range identified high turnover. Lower calcium values (Ca < 8.7 mg/dL) were correlated with mineralization defects. On the other hand, FGF-23, OPG, and RANKL did not impact the turnover and mineralization. While bone histomorphometry is not widely available, bone biomarkers such as BSAP, P1NP, PTH, and calcium allow the assessment of turnover and mineralization defects in HD patients. Then, using bone biomarkers may help clinicians define treatments for ROD and osteoporosis and monitor therapeutic response.

High-resolution peripheral quantitative computed tomography: research or clinical practice?

High-resolution peripheral quantitative CT (HR-pQCT) is a low-dose three-dimensional imaging technique, originally developed for in vivo assessment of bone microarchitecture at the distal radius and tibia in osteoporosis. HR-pQCT has the ability to discriminate trabecular and cortical bone compartments, providing densitometric and structural parameters. At present, HR-pQCT is mostly used in research settings, despite evidence showing that it may be a valuable tool in osteoporosis and other diseases. This review summarizes the main applications of HR-pQCT and addresses the limitations that currently prevent its integration into routine clinical practice. In particular, the focus is on the use of HR-pQCT in primary and secondary osteoporosis, chronic kidney disease (CKD), endocrine disorders affecting bone, and rare diseases. A section on novel potential applications of HR-pQCT is also present, including assessment of rheumatic diseases, knee osteoarthritis, distal radius/scaphoid fractures, vascular calcifications, effect of medications, and skeletal muscle. The reviewed literature seems to suggest that a more widespread implementation of HR-pQCT in clinical practice would offer notable opportunities. For instance, HR-pQCT can improve the prediction of incident fractures beyond areal bone mineral density provided by dual-energy X-ray absorptiometry. In addition, HR-pQCT may be used for the monitoring of anti-osteoporotic therapy or for the assessment of mineral and bone disorder associated with CKD. Nevertheless, several obstacles currently prevent a broader use of HR-pQCT and would need to be targeted, such as the small number of installed machines worldwide, the uncertain cost-effectiveness, the need for improved reproducibility, and the limited availability of reference normative data sets.

Correlations between radiological and histological findings of bone remodelling and root resorption in a rodent cleft model

Background

The evaluation of bone remodelling and dental root resorption can be performed by histological techniques or micro-computed tomography (micro-CT). The present study aimed to evaluate the relationship between these two procedures in the context of cleft repair in a rat model.

Methods

The reconstructed maxillae and the orthodontically-moved first molar of 12 rats were analysed for correlations between the histological and radiological findings retrospectively. The alveolar cleft repairs were performed using bone autografts or (human) xenografts. Four weeks after the operation, the intervention of the first molar protraction was initiated and lasted for eight weeks. The newly formed bone and the root resorption lacunae were determined via histology. In the micro-CT analysis, the average change of bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness and trabecular separation of the jaw, as well as the volume of the root resorptions were determined. The Pearson correlation coefficient was applied to study the associations between groups.

Results

Positive correlations were found only between the newly formed bone (histology) and BMD changes (micro-CT) in the autograft group (r = 0.812, 95% CI: 0.001 to 0.979, p = 0.05). The relationship of newly formed bone and BV/TV was similar but not statistically significant (r = 0.691, 95% CI: −0.274 to 0.963, p = 0.013). Regarding root resorption, no significant correlations were found.

Conclusions

Due to the lack of correlation between histological and radiological findings of bone remodelling and the development of root resorptions, both methods should be combined in this cleft model in rats for a comprehensive analysis.