Cortical bone analysis in a predialysis population: a comparison with a dialysis population

Risk factors and clinical prediction models for osteoporosis in pre-dialysis chronic kidney disease patients

BACKGROUND

Osteoporosis in pre-dialysis chronic kidney disease (CKD) patients has been overlooked, and the risk factors of osteoporosis in these patients have not been adequately studied.

OBJECTIVE

To identify risk factors for osteoporosis in pre-dialysis CKD patients and develop predictive models to estimate the likelihood of osteoporosis.

METHODS

Dual-energy X-ray absorptiometry was used to measure bone mineral density, and clinical examination results were collected from 326 pre-dialysis CKD patients. Binary logistic regression was employed to explore the risk factors associated with osteoporosis and develop predictive models.

RESULTS

In this cohort, 53.4% (n = 174) were male, 46.6% (n = 152) were female, and 21.8% (n = 71) were diagnosed with osteoporosis. Among those diagnosed with osteoporosis, 67.6% (n = 48) were female and 32.4% (n = 23) were male. Older age and low 25-(OH)-Vitamin D levels were identified as risk factors for osteoporosis in males. For females, older age, being underweight, higher bone alkaline phosphatase (NBAP), and advanced CKD (G5) were significant risk factors, while higher iPTH was protective. Older age, being underweight, and higher NBAP were risk factors for osteoporosis in the G1-4 subgroup. In the G5 subgroup, older age and higher NBAP increased the risk, while high 25-(OH)-Vitamin D or iPTH had protective effects. Nomogram models were developed to assess osteoporosis risk in pre-dialysis patients based on gender and renal function stage.

CONCLUSION

Risk factors for osteoporosis vary by gender and renal function stages. The nomogram clinical prediction models we constructed may aid in the rapid screening of patients at high risk of osteoporosis.

Poor prognosis and risk factors of nonoperative treatment hip fracture patients with end-stage renal disease

This study aims to summarize the prognosis and risk factors of nonoperative treatment patients of hip fracture with end-stage renal disease (ESRD). A total of 113 individuals of hip fracture with nonoperative treatment were retrospectively enrolled, 38 patients with ESRD were defined as the observation group, and the other 75 patients without ESRD were served as the control group. The difference in 30-day and 1-year mortality rate between the 2 groups was compared. The effects of risk factors on survival were estimated by the Cox proportional-hazards model. The survival difference was estimated by the method of Kaplan-Meier. In the subsequent subgroup analysis of the observation group, as before, the Cox proportional-hazards model and the Kaplan-Meier method were used. The 1-year mortality rate of the observation group was considerably higher than that of the control group, which was 86.84% and 32.0%, respectively (P < .005). For nonoperative treatment hip fracture subjects, ESRD, age ≥ 82, BMI (BMI) < 20, high Charlson Comorbidity Index (CCI) and low Barthel Index (BI) were associated with a low survival curve (P < .05). In the subsequent multivariable subgroup analyses, for nonoperative treatment hip fracture subjects with ESRD, high CCI and low BI were also the independent risk factors of mortality. For nonoperative treatment hip fracture subjects, ESRD, old age, low BMI, high CCI and low BI were the independent risk factors of mortality. For hip fracture subjects with ESRD, nonoperative treatment was associated with excess high 1-year mortality rate, especially for patients with high CCI and low BI.

Incident vertebral fracture and longitudinal BMD change in Chinese postmenopausal women with early CKD: Peking Vertebral Fracture Study

Early chronic kidney disease (CKD) and non-CKD individuals had similar morphometric vertebral fracture (mVF) incidence and longitudinal bone mineral density (BMD) change. CKD did not modify the association between BMD and incident mVF status. Patients with a higher baseline BMD had a higher longitudinal BMD loss in early CKD.

PURPOSE

The aim of this 5-year longitudinal cohort study was to compare the risk of incident morphometric vertebral fracture (mVF) and longitudinal bone mineral density (BMD) change between individuals with early chronic kidney disease (CKD) and those without CKD.

METHODS

A total of 869 Chinese postmenopausal women were enrolled in the study. Serum creatinine levels were assessed using standard methods, and estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Incident mVF was confirmed through lateral radiographs of the thoracolumbar spine. BMDs at the lumbar spine (LS) and femoral neck (FN) were measured using dual-energy X-ray absorptiometry. CKD was defined based on eGFR values: 60-89 mL/min/1.73m2 for stage 2 (n = 511) and 30-59 mL/min/1.73m2 for stage 3 (n = 92). The non-CKD group included individuals with an eGFR greater than or equal to 90 mL/min/1.73m2.

RESULTS

The incidence of mVF was not statistically different between individuals with early CKD and those without CKD (4.1% in non-CKD, 6.3% in CKD stage 2, and 7.6% in CKD stage 3; p = 0.348). Neither eGFR nor CKD status was significantly associated with incident mVF in the multivariate logistic regression analysis. Baseline BMD T-scores were negatively associated with incident mVF (LS T-score, OR = 0.603, 95% CI = 0.468-0.777; FN T-score, OR = 0.511, 95% CI = 0.350-0.746). No evidence of interaction between BMD T-scores and CKD status were identified (p = 0.284-0.785) . The differences in longitudinal BMD changes between non-CKD and CKD groups were comparable (FN BMD: -6.31 ± 7.20% in non-CKD, -5.07 ± 8.20% in CKD stage 2, and -4.49 ± 8.40% in CKD stage 3, p = 0.556; LS BMD: -1.38 ± 8.18% in non-CKD, -0.32 ± 7.14% in CKD stage 2, and 1.5 ± 6.97% in CKD stage 3, p = 0.406). Individuals with a higher baseline FN BMD showed a greater longitudinal FN BMD loss (r = -0.185, p < 0.001) .

CONCLUSIONS

Our study revealed that early CKD was not associated with an increased risk of incident mVF or greater longitudinal BMD loss. Moreover, CKD did not modify the association between BMD and the risk of incident mVF, suggesting that the management and prevention of fractures in early CKD should be approached similarly to those without CKD. Measurement of BMD appears to be crucial for predicting incident mVF risk and longitudinal bone loss in early CKD.

A novel murine model of combined insulin-dependent diabetes and chronic kidney disease has greater skeletal detriments than either disease individually

Diabetes and chronic kidney disease (CKD) consistently rank among the top ten conditions in prevalence and mortality in the United States. Insulin-dependent diabetes (IDD) and CKD each increase the risk of skeletal fractures and fracture-related mortality. However, it remains unknown whether these conditions have interactive end-organ effects on the skeleton. We hypothesized that combining IDD and CKD in mice would cause structural and mechanical bone alterations that are more deleterious compared to the single disease states. Female C57BL6/J mice were divided into four groups: 1) N = 12 Control (CTRL), 2) N = 10 Streptozotocin-induced IDD (STZ), 3) N = 10 Adenine diet-induced CKD (AD), and 4) N = 9 Combination (STZ+AD). STZ administration resulted in significantly higher blood glucose, HbA1c (p < 0.0001), and glucose intolerance (p < 0.0001). AD resulted in higher blood urea nitrogen (p = 0.0002) while AD, but not STZ+AD mice, had high serum parathyroid hormone (p < 0.0001) and phosphorus (p = 0.0005). STZ lowered bone turnover (p = 0.001). Trabecular bone volume was lowered by STZ (p < 0.0001) and increased by AD (p = 0.003). Tissue mineral density was lowered by STZ (p < 0.0001) and AD (p = 0.02) in trabecular bone but only lowered by STZ in cortical bone (p = 0.002). Cortical porosity of the proximal tibia was increased by AD, moment of inertia was lower in both disease groups, and most cortical properties were lower in all groups vs CTRL. Ultimate force, stiffness, toughness, and total displacement/strain were lowered by STZ and AD. Fracture toughness was lower by AD (p = 0.003). Importantly, Cohen's D indicated that STZ+AD most strongly lowered bone turnover and mechanical properties. Taken together, structural and material-level bone properties are altered by STZ and AD while their combination resulted in greater detriments, indicating that improving bone health in the combined disease state may require novel interventions.

Significant associations between bone mineral density and vascular calcification in patients with different stages of chronic kidney disease

Introduction

Chronic kidney disease—mineral and bone disorders (CKD-MBD) is characterised by generalised vascular calcification (VC) and impaired bone health. We aimed to investigate the relationship between VC and bone mineral density (BMD) in CKD patients.

Methods

We performed a cross-sectional study of patients with different stages of CKD. For assessment of VC of abdominal aorta lateral lumbar X-rays (Kauppila score), the ankle-brachial index (ABI) and echocardiography were used. Total body densitometry provided BMD.

Results

Ninety patients (41% male, median age 64 years (range 29–87)) were included, of whom 41.1% had a Kauppila score > 1. Evidence of peripheral VC as measured by ABI was detected in 23.3% of cases. Lesions of the heart valves were found in 46.7% of patients. There was a significant association between high ABI and lesions of the heart valves. In the multivariate regression model to analyse the independent determinants of abdominal aorta calcification (AAC) and ABI, the BMD of the femoral neck was identified as significant for both (p = 0.001, p = 0.001). The total spine BMD was found to be significant for AAC (p = 0.001), and the BMD of spine L1-L4 and the ribs were found to be significant for ABI (p = 0.01, p = 0.002 respectively). In factorial regression analysis, where BMD was independent determinant, valvular calcification was significant for BMD of femur, femoral neck and total BMD. Age and tALP were inversely correlated with the BMD of femur and femoral neck.

Conclusions

Our work highlighted clinically important relationships between VC and bone mineral density (BMD) in CKD patients. We detected inverse relationships between AAC, high ABI and BMD. Secondly, BMD at certain bone sites (femur, femoral neck) and total BMD were associated with important lesions of heart valves. Thirdly, a significant association between a high ABI and lesions of the heart valves. We believe that the results of our study will help in the planning of future research and in current clinical practice for the early diagnosis, further monitoring and management of CKD-MBD. Additionally, these results may have treatment implications on use of different CKD-MBD medications.

Osteoporosis, an Inevitable Circumstance of Chronic Kidney Disease: A Systematic Review

Nowadays, chronic kidney disease (CKD) and osteoporosis have become crucial health-related issues globally. CKD-induced osteoporosis is a systemic disease characterized by the disruption of mineral, hormone, and vitamin homeostasis that elevates the likelihood of fracture. Here, we review recent studies on the association of CKD and osteoporosis. In particular, we focus on the pathogenesis of CKD-associated osteoporosis, including the homeostasis and pathways of several components such as parathyroid hormone, calcium, phosphate, vitamin D, fibroblast growth factor, and klotho, as well as abnormal bone mineralization, remodeling, and turnover. In addition, we explore the diagnostic tools and possible therapeutic approaches for the management and prevention of CKD-associated osteoporosis. Patients with CKD show higher osteoporosis prevalence, greater fracture rate, increased morbidity and mortality, and an elevated occurrence of hip fracture. We also rule out that increased severity of CKD is related to a more severe condition of osteoporosis. Furthermore, supplements such as calcium and vitamin D as well as lifestyle modifications such as exercise and cessation of smoking and alcohol help in fracture prevention. However, new approaches and advancements in treatment are needed to reduce the fracture risk in patients with CKD. Therefore, further collaborative multidisciplinary research is needed in this regard.

The Use of Imaging Techniques in Chronic Kidney Disease-Mineral and Bone Disorders (CKD-MBD)-A Systematic Review

Although frequently silent, mineral and bone disease (MBD) is one of the most precocious complication of chronic kidney disease (CKD) and is omnipresent in patients with CKD stage 5. Its pathophysiology is complex, but basically, disturbances in vitamin D, phosphate, and calcium metabolism lead to a diverse range of clinical manifestations with secondary hyperparathyroidism usually being the most frequent. With the decline in renal function, CKD-MBD may induce microstructural changes in bone, vascular system and soft tissues, which results in macrostructural lesions, such as low bone mineral density (BMD) resulting in skeletal fractures, vascular and soft tissue calcifications. Moreover, low BMD, fractures, and vascular calcifications are linked with increased risk of cardiovascular mortality and all-cause mortality. Therefore, a better characterization of CKD-MBD patterns, beyond biochemical markers, is helpful to adapt therapies and monitor strategies as used in the general population. An in-depth characterization of bone health is required, which includes an evaluation of cortical and trabecular bone structure and density and the degree of bone remodeling through bone biomarkers. Standard radiological imaging is generally used for the diagnosis of fracture or pseudo-fractures, vascular calcifications and other features of CKD-MBD. However, bone fractures can also be diagnosed using computed tomography (CT) scan, magnetic resonance (MR) imaging and vertebral fracture assessment (VFA). Fracture risk can be predicted by bone densitometry using dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (QTC) and peripheral quantitative computed tomography (pQTC), quantitative ultrasound (QUS) and most recently magnetic resonance micro-imaging. Quantitative methods to assess bone consistency and strength complete the study and adjust the clinical management when integrated with clinical factors. The aim of this review is to provide a brief and comprehensive update of imaging techniques available for the diagnosis, prevention, treatment and monitoring of CKD-MBD.

Adenine-induced chronic kidney disease induces a similar skeletal phenotype in male and female C57BL/6 mice with more severe deficits in cortical bone properties of male mice

Chronic kidney disease (CKD) causes bone loss, particularly in cortical bone, through formation of cortical pores which lead to skeletal fragility. Animal models of CKD have shown variability in the skeletal response to CKD between males and females suggesting sex may play a role in this variation. Our aim was to compare the impact of adenine-induced CKD on cortical parameters in skeletally mature male and female C57Bl/6 mice. After 10-weeks of adenine-induced CKD, both male and female adenine mice had high serum parathyroid hormone (PTH), high bone turnover, and cortical porosity compared to non-CKD controls. Both sexes had lower cortical thickness, but only male mice had lower cortical bone area. CKD imparted greater deficits in mechanical properties of male mice compared to female mice. These data demonstrate that both male and female mice develop high PTH/high bone turnover in response to adenine-induced CKD and that cortical bone phenotypes are slightly more severe in males, particularly in mechanical properties deficits.

Vascular calcification relationship to vascular biomarkers and bone metabolism in advanced chronic kidney disease

BACKGROUND

Vascular calcification (VC) and renal osteodystrophy are important complications of advanced chronic kidney disease (CKD). High resolution peripheral quantitative computed tomography (HRpQCT) is able to assess bone microstructure in renal osteodystrophy and lower leg arterial calcification (LLAC) is usually seen as an incidental finding. LLAC can be a useful quantitative assessment of VC in CKD but the relationship between LLAC and vascular biomarkers and bone is unknown. We aimed to assess the relationship between LLAC and biomarkers, bone turnover and microstructure.

METHODS

In this cross-sectional study, fasting blood samples were taken from 69 CKD stages 4-5D patients and 68 healthy controls. HRpQCT of distal tibia and radius were performed. 43 CKD patients had trans-iliac bone biopsy after tetracycline labelling.

RESULTS

LLAC was more severe in CKD than controls (median [IQR] 1.043 [0.05-16.52] vs 0 [0-0.55] mgHA, p < 0.001). CKD patients with diabetes (28%) had significantly higher LLAC compared to non-diabetic CKD (median [IQR] 24.07 [3.42-61.30] vs 0.23 [0-3.78] mgHA, p < 0.001). LLAC mass in CKD correlated with serum phosphate (rho = 0.29, p < 0.05), calcium x phosphate product (rho = 0.31, p < 0.05), intact parathyroid hormone (rho = 0.38, p < 0.01), intact fibroblast growth factor-23 (iFGF23) (rho = 0.40, p = 0.001), total alkaline phosphatase (rho = 0.41, p < 0.001), bone alkaline phosphatase (rho = 0.29, p < 0.05), osteocalcin (rho = 0.32, p < 0.05), osteoprotegerin (rho = 0.40, p = 0.001) and dephosphorylated-uncarboxylated matrix Gla protein (rho = 0.31, p < 0.05). LLAC in CKD also correlated with worse distal tibia cortical bone mineral density, thickness and porosity. No association was found between LLAC and bone turnover, mineralization or volume on biopsy in CKD. In multivariate analysis, only age, diabetes, iPTH and iFGF23 were independently associated with LLAC in CKD.

CONCLUSIONS

High levels of PTH and FGF23, along with older age and the presence of diabetes may all play independent roles in the development of LLAC in advanced CKD.

CKD Stages, Bone Metabolism Markers, and Cortical Porosity Index: Associations and Mediation Effects Analysis

Chronic kidney disease (CKD) has a significant negative impact on bone health. However, the mechanisms of cortical bone deterioration and cortical porosity enlargement caused by CKD have not been fully described. We therefore examined the association of CKD stages with cortical porosity index (PI), and explored potential mediators of this association. Double-echo ultrashort echo-time magnetic resonance imaging (UTE MRI) provides the possibility of quantifying cortical porosity in vivo. A total of 95 patients with CKD stages 2-5 underwent 3D double-echo UTE-Cones MRI (3.0T) of the midshaft tibia to obtain the PI. PI was defined as the ratio of the image signal intensity of a sufficiently long echo time (TE) to the shortest achievable TE. Parathyroid hormone (PTH), β-CrossLaps (β-CTX), total procollagen type I amino-terminal propeptide (T-P1NP), osteocalcin (OC), 25-hydroxyvitamin D (25OHD), and lumbar bone mineral density (BMD) were measured within one week of the MRI. Partial correlation analysis was performed to address associations between PI, eGFR and potential mediators (PTH, β-CTX, T-P1NP, OC, 25OHD, BMD, and T-score). Multiple linear regression models were used to assess the association between CKD stages and PI value. Then, a separate exploratory mediation analysis was carried out to explore the impact of CKD stages and mediators on the PI value. The increasing CKD stages were associated with a higher PI value (P_trend < 0.001). The association of CKD stages and PI mediated 34.4% and 30.8% of the total effect by increased PTH and β-CTX, respectively. Our study provides a new idea to monitor bone health in patients with CKD, and reveals the internal mechanism of bone deterioration caused by CKD to some extent.

Kidney Disease and Bone: Changing the Way We Look at Skeletal Health

PURPOSE OF REVIEW

Kidney disease imparts profound skeletal changes, and unlike many other skeletal diseases, cortical bone is predominantly impacted. Significant advances in medical imaging have led to our ability to now obtain high-resolution three-dimensional views of cortical bone. This paper overviews recent work focused on cortical bone imaging, specifically cortical porosity, in kidney disease.

RECENT FINDINGS

Although a number of clinical papers have used high-resolution imaging to assess cortical bone porosity, the most impactful work involves longitudinal study designs that have assessed cortical porosity changes over time. These latter studies demonstrate dramatic increases in cortical porosity in untreated individuals and a lack of clear efficacy in reversing porosity with treatment (although data are limited). Those papers providing longitudinal assessment, both clinical and pre-clinical, reveal powerful data about cortical porosity and provide a foundation upon which future studies can build.

Bone mineral density and mortality in end-stage renal disease patients

Osteoporosis characterized by low bone mineral density (BMD) as assessed by dual-energy X-ray absorptiometry (DXA) is common among end-stage renal disease (ESRD) patients and associates with high fracture incidence and high all-cause mortality. This is because chronic kidney disease-mineral bone disorders (CKD-MBDs) promote not only bone disease (osteoporosis and renal dystrophy) but also vascular calcification and cardiovascular disease. The disturbed bone metabolism in ESRD leads to 'loss of cortical bone' with increased cortical porosity and thinning of cortical bone rather than to loss of trabecular bone. Low BMD, especially at cortical-rich bone sites, is closely linked to CKD-MBD, vascular calcification and poor cardiovascular outcomes. These effects appear to be largely mediated by shared mechanistic pathways via the 'bone-vascular axis' through which impaired bone status associates with changes in the vascular wall. Thus, bone is more than just the scaffolding that holds the body together and protects organs from external forces but is-in addition to its physical supportive function-also an active endocrine organ that interacts with the vasculature by paracrine and endocrine factors through pathways including Wnt signalling, osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/RANK ligand system and the Galectin-3/receptor of advanced glycation end products axis. The insight that osteogenesis and vascular calcification share many similarities-and the knowledge that vascular calcification is a cell-mediated active rather than a passive mineralization process-suggest that low BMD and vascular calcification ('vascular ossification') to a large extent represent two sides of the same coin. Here, we briefly review changes of BMD in ESRD as observed using different DXA methods (central and whole-body DXA) at different bone sites for BMD measurements, and summarize recent knowledge regarding the relationships between 'low BMD' and 'fracture incidence, vascular calcification and increased mortality' in ESRD patients, as well as potential 'molecular mechanisms' underlying these associations.

A microRNA Approach to Discriminate Cortical Low Bone Turnover in Renal Osteodystrophy

A main obstacle to diagnose and manage renal osteodystrophy (ROD) is the identification of intracortical bone turnover type (low, normal, high). The gold standard, tetracycline‐labeled transiliac crest bone biopsy, is impractical to obtain in most patients. The Kidney Disease Improving Global Outcomes Guidelines recommend PTH and bone‐specific alkaline phosphatase (BSAP) for the diagnosis of turnover type. However, PTH and BSAP have insufficient diagnostic accuracy to differentiate low from non‐low turnover and were validated for trabecular turnover. We hypothesized that four circulating microRNAs (miRNAs) that regulate osteoblast (miRNA‐30b, 30c, 125b) and osteoclast development (miRNA‐155) would provide superior discrimination of low from non‐low turnover than biomarkers in clinical use. In 23 patients with CKD 3‐5D, we obtained tetracycline‐labeled transiliac crest bone biopsy and measured circulating levels of intact PTH, BSAP, and miRNA‐30b, 30c, 125b, and 155. Spearman correlations assessed relationships between miRNAs and histomorphometry and PTH and BSAP. Diagnostic test characteristics for discriminating low from non‐low intracortical turnover were determined by receiver operator curve analysis; areas under the curve (AUC) were compared by χ² test. In CKD rat models of low and high turnover ROD, we performed histomorphometry and determined the expression of bone tissue miRNAs. Circulating miRNAs moderately correlated with bone formation rate and adjusted apposition rate at the endo‐ and intracortical envelopes (ρ = 0.43 to 0.51; p < 0.05). Discrimination of low versus non‐low turnover was 0.866, 0.813, 0.813, and 0.723 for miRNA‐30b, 30c, 125b, and 155, respectively, and 0.509 and 0.589 for PTH and BSAP, respectively. For all four miRNAs combined, the AUC was 0.929, which was superior to that of PTH and BSAP alone and together (p < 0.05). In CKD rats, bone tissue levels of the four miRNAs reflected the findings in human serum. These data suggest that a panel of circulating miRNAs provide accurate noninvasive identification of bone turnover in ROD. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Updates in CKD-Associated Osteoporosis

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is associated with bone loss and fractures. The purpose of this review is to provide clinicians with an overview of the underlying pathogenesis of CKD-associated osteoporosis, and a summary of the current diagnostic and therapeutic approaches to this disease.

RECENT FINDINGS

In 2017, the Kidney Disease Improving Global Outcomes Committee on Bone Quality updated their guidelines to include screening for osteoporosis and fracture risk by dual energy X-ray absorptiometry in patients with CKD. Once a diagnosis of osteoporosis and/or fracture risk is established, it is not clear how nephrologists should manage their patients. Patients with CKD should be screened for CKD-associated osteoporosis and considered for strategies that prevent bone loss and fractures. Assessment of bone turnover via imaging, biochemical testing, or bone biopsy can help guide the choice of therapy. Randomized controlled trials are needed to assess safety and efficacy of treatments to prevent bone loss and fractures.

Rethinking Bone Disease in Kidney Disease

Renal osteodystrophy (ROD) is the bone component of chronic kidney disease mineral and bone disorder (CKD-MBD). ROD affects bone quality and strength through the numerous hormonal and metabolic disturbances that occur in patients with kidney disease. Collectively these disorders in bone quality increase fracture risk in CKD patients compared with the general population. Fractures are a serious complication of kidney disease and are associated with higher morbidity and mortality compared with the general population. Furthermore, at a population level, fractures are at historically high levels in patients with end-stage kidney disease (ESKD), whereas in contrast the general population has experienced a steady decline in fracture incidence rates. Based on these findings, it is clear that a paradigm shift is needed in our approach to diagnosing and managing ROD. In clinical practice, our ability to diagnose ROD and initiate antifracture treatments is impeded by the lack of accurate noninvasive methods that identify ROD type. The past decade has seen advances in the noninvasive measurement of bone quality and strength that have been studied in kidney disease patients. Below we review the current literature pertaining to the epidemiology, pathology, diagnosis, and management of ROD. We aim to highlight the pressing need for a greater awareness of this condition and the need for the implementation of strategies that prevent fractures in kidney disease patients. Research is needed for more accurate noninvasive assessment of ROD type, clinical studies of existing osteoporosis therapies in patients across the spectrum of kidney disease, and the development of CKD-specific treatments. © 2018 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Predictors of bone fractures in a single-centre cohort of hemodialysis patients: a 2-year follow-up study

PURPOSE

Bone involvement represents one of the complications of end-stage chronic kidney disease, with fractures being its major risk. The aim of our study was to assess the frequency and predictors of low-trauma fractures in a cohort of maintenance hemodialysis patients followed-up on for 2 years.

METHODS

59 patients (67.6 ± 13.1 years, 43 males) treated with hemodiafiltration underwent initially laboratory (markers of calcium-phosphate metabolism and bone turnover markers) and densitometry examination with TBS assessment (Lunar Prodigy, TBS software 2.1.2). During 24-month follow-up, the frequency of low-trauma fractures was assessed and possible predictors of increased fracture risk were identified using product-moment correlation matrices.

RESULTS

Altogether 7 (11.9%) low-trauma fractures were observed. In the whole group, age (P = 0.047), T-score in proximal femur (P = 0.04), low vitamin D, low BMI (P = 0.03 for both), and higher FRAX for major osteoporotic fracture (P = 0.01) were connected with fractures, but in multi-variate analysis only BMI remained significantly negatively associated with fractures (P = 0.047). TBS and bone turnover markers failed to predict fractures. However, women with fractures had significantly lower serum phosphate (P = 0.03) and higher parathyroid hormone (P = 0.04). Parameters of hip structure analysis significantly correlated with FRAX, but not with fractures.

CONCLUSIONS

In a group of hemodialysis patients from one centre, T-score in proximal femur, low vitamin D, low BMI, and high FRAX for major osteoporotic fracture were associated with low-trauma fractures, however, in multi-variate analysis only low BMI remained a significant predictor of fracture risk.

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

BACKGROUND

Cortical bone is a significant determinant of bone strength and its deterioration contributes to bone fragility. Thin cortices and increased cortical porosity have been noted in patients with chronic kidney disease (CKD), but the "Turnover Mineralization Volume" classification of renal osteodystrophy does not emphasize cortical bone as a key parameter. We aimed to assess trabecular and cortical bone microarchitecture by histomorphometry and micro-CT in patients with CKD G5 and 5D (dialysis).

METHODS

Transiliac bone biopsies were performed in 14 patients undergoing kidney transplantation (n = 12) and parathyroidectomy (n = 2). Structural parameters were analysed by histomorphometry and micro-CT including trabecular bone volume, thickness (TbTh), number (TbN) and separation and cortical thickness (CtTh) and porosity (CtPo). Indices of bone remodelling and mineralisation were obtained and relationships to bone biomarkers examined. Associations were determined by Spearman's or Pearson's rank correlation coefficients.

RESULTS

By micro-CT, trabecular parameters were within normal ranges in most patients, but all patients showed very low CtTh (127 ± 44 µm) and high CtPo (60.3 ± 22.5%). CtPo was inversely related to TbN (r = -0.56; p = 0.03) by micro-CT and to TbTh (r = -0.60; p = 0.024) by histomorphometry and correlated to parathyroid hormone values (r = 0.62; p = 0.021). By histomorphometry, bone turnover was high in 50%, low in 21% and normal in 29%, while 36% showed abnormal patterns of mineralization. Significant positive associations were observed between osteoblast surface, osteoclast surface, mineralization surface and bone turnover markers.

CONCLUSIONS

Deterioration of cortical -microarchitecture despite predominantly normal trabecular parameters reinforces the importance of comprehensive cortical evaluation in patients with CKD.

Two-year cortical and trabecular bone loss in CKD-5D: biochemical and clinical predictors

This prospective two-year study of patients on chronic dialysis measured changes in bone mineral density (BMD). Patients with higher baseline BMD and shorter dialysis vintage lost more bone. Treatment with anti-hypertensives acting on the central nervous system was protective against bone loss. Baseline serum levels of sclerostin and bone-specific alkaline phosphatase predicted bone loss.

INTRODUCTION

This prospective 2-year study of chronic kidney disease on dialysis (CKD-5D) patients assessed trabecular and cortical bone loss at the hip and spine and examined potential demographic, clinical, and serum biochemical predictors of bone loss.

METHODS

Eighty-nine CKD-5D patients had baseline, year 1, and year 2 bone mineral density (BMD) measurements using dual X-ray absorptiometry (DXA) and quantitative computed tomography (QCT); concurrent blood samples were drawn and clinical variables recorded. No study treatments occurred.

RESULTS

The 2-year total hip BMD change was - 5.9% by QCT and - 3.1% by DXA (p < 0.001). Spinal BMD was unchanged. QCT total hip cortical mass and volume decreased (- 7.3 and - 10.0%); trabecular volume increased by 5.9% (ps < 0.001). BMD changes did not vary with age, BMI, race, diabetes, smoking, or exercise. Patients with higher baseline BMD and shorter dialysis vintage lost more bone (p < 0.05). Vitamin D analogs and phosphate binders were not protective against bone loss; cinacalcet was protective by univariate but not by multivariable analysis. CNS-affecting antihypertensives were protective against loss of BMD, cortical mass, cortical volume (ps < 0.05) and trabecular mass (p = 0.007). These effects remained after adjustment. BSAP correlated with changes in BMD, cortical mass, and volume (p < 0.01) as did sclerostin (inversely).

CONCLUSIONS

There was severe cortical bone loss at the hip best recognized by QCT. Patients with shorter dialysis vintage and less pre-existing bone loss lost more bone, while treatment with CNS-acting antihypertensives was protective. BSAP and sclerostin were useful markers of bone loss.