Bone Quality Assessment as Measured by Trabecular Bone Score in Patients With End-Stage Renal Disease on Dialysis

Comprehensive evaluation of bone health among kidney transplant recipients - A prospective, single center, observational cohort study from India

BACKGROUND

There is a paucity of studies describing trabecular bone score (TBS) and bone mineral density (BMD) in kidney transplant (KT) recipients from developing countries.

STUDY SETTING

This prospective observational study, from a tertiary teaching hospital in India assessed clinical, biochemical parameters including bone turnover markers and dual-energy X-ray absorptiometry (DXA) for BMD/TBS, hip structural analysis (HSA) and vertebral fracture assessment (VFA) at pre-KT, 3 months and 12 months post-KT.

RESULTS

A total of 53 KT recipients (90.6% living related) were recruited from August 2019 to March 2020 and followed till 1-year post-KT. The mean age was 33.9±10.4 years, 71.7% were males, and 11.5% had a history of pre-KT steroid use. Baseline fractures pre-KT as assessed by VFA were seen in 4 patients (7.5%). Mean BMD at spine and femoral neck and HSA variables at narrow neck and femoral shaft continued to decline till 3 months, but stabilised and reached pre-KT values 12 months post-KT. However, TBS and bone turn over markers continued to decline till 12 months post-KT (p value <0.001). New onset vertebral fractures were seen in 2(3.7%) and 1 patient (2.3%) at 3- and 12-months post-KT respectively. Pre-KT BMD significantly influenced bone health at 12 months post-KT, with patients in each quartile maintaining a similar trajectory over the follow up period (p < 0.001).

CONCLUSION

Despite significant improvement in kidney function following transplant, TBS and BMD of the spine significantly decreased mainly in the early post-KT period suggesting the effect of immunosuppressants on the bone. Strategies to improve bone health in KT patients are warranted.

Trabecular Bone Score as a Marker of Skeletal Fragility Across the Spectrum of Chronic Kidney Disease: A Systematic Review and Meta-analysis

CONTEXT

The impairment of bone microarchitecture is a key determinant of skeletal fragility in patients with chronic kidney disease (CKD). The trabecular bone score (TBS) has been developed as a reliable noninvasive index of bone quality. However, its utility in this setting is still debated.

OBJECTIVE

The aim of this systematic review and meta-analysis was to summarize the available evidence about TBS as a marker of skeletal fragility across the spectrum of CKD.

METHODS

PubMed/Medline, EMBASE, and Cochrane Library databases were systematically searched until July 2023 for studies reporting data about TBS in patients with CKD. Effect sizes were pooled through a random-effect model.

RESULTS

Compared to controls, lower TBS values were observed in CKD patients not on dialysis (-0.057, 95%CI:[-0.090, -0.024], P < .01), in dialysis patients (-0.106, 95%CI:[-0.141, -0.070], P < .01), and in kidney transplant recipients (KTRs) (-0.058, 95%CI:[-0.103, -0.012], P = .01). With respect to fracture risk, TBS was able to predict incident fractures in nondialysis patients at unadjusted analyses (hazard ratio [HR] per SD decrease: 1.45, 95%CI:[1.05, 2.00], P = .02), though only a nonsignificant trend was maintained when fully adjusting the model for FRAX® (HR = 1.26, 95%CI:[0.88, 1.80], P = .21). Dialysis patients with prevalent fractures had lower TBS values compared to unfractured ones (-0.070, 95% CI:[-0.111, -0.028], P < .01). Some studies supported a correlation between TBS and fracture risk in KTRs, but results could not be pooled due to the lack of sufficient data.

CONCLUSION

CKD patients are characterized by an impairment of bone microarchitecture, as demonstrated by lower TBS values, across the whole spectrum of kidney disease. TBS can also be helpful in the discrimination of fracture risk, with lower values being correlated with a higher risk of prevalent and incident fractures.

Bibliometric analysis of publications on trabecular bone score (TBS)

Purpose

Trabecular bone score (TBS), as a texture indicator of bone microarchitecture, predicts the risk of fracture. This study aims to explore the knowledge map of TBS.

Methods

We searched Scopus for "trabecular bone score" or "trabecular score" from the beginning to 2021. Our inclusion criteria were original articles and reviews that were related to TBS and our exclusion criteria were non-English articles, non-related to TBS, and document type other than original articles and reviews. and related documents were included for bibliometric analysis. Excel, VOS viewer, and Science of Science (Sci2) software were used for data synthesis.

Results

From 749 retrieved articles, 652 articles were included for analysis. These documents were cited 12,153 times and had an H-index of 56. The most productivity belonged to the USA (n = 130 documents), Switzerland (n = 101), and Italy (n = 67). "Osteoporosis International" (n = 80) had the highest participation in publishing. The research topics of interest were mainly related to the applicability of TBS for fracture risk assessment in chronic endocrine disorders such as osteoporosis and diabetes mellitus. Bursting analysis of the title and abstract revealed the initial focus of the discriminative power of TBS for osteoporotic fracture and the more recent focus on comparing bone mineral density (BMD) and TBS in a variety of chronic diseases.

Conclusion

The number of annual publications on TBS has increased, especially after 2016. These publications highlight the importance of in-depth knowledge of TBS in predicting fracture risk and also its strengths and limitations of treatment monitoring in different health conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01338-7.

Trabecular Bone Score Improves Fracture Risk Discrimination in Postmenopausal Rheumatoid Arthritis Patients Receiving Glucocorticoids

Background

Bone mineral density (BMD) might not be a sensitive tool for predicting osteoporotic fracture risk among patients with rheumatoid arthritis (RA), especially when receiving glucocorticoids. Trabecular bone score (TBS), which has emerged as a new assessment technique representing bone microarchitecture and strength, may be considered an alternative approach.

Materials and Methods

In this cross-sectional analytical study, postmenopausal RA patients receiving glucocorticoids were identified from the postmenopause BMD database. The database included clinical data of postmenopausal outpatients who had at least one BMD measurement between January 2014 and December 2017. TBS was calculated from lumbar spine BMD with the microarchitecture assessment software. The presence of osteoporotic fractures, either vertebral or non-vertebral, was identified at the time of BMD measurement.

Results

A total of 64 postmenopausal RA patients receiving glucocorticoids were included. The TBS values were inversely associated with osteoporotic fractures, with a TBS cut-off of less than 1.24, showing the best accuracy with a sensitivity of 79% and a specificity of 84% in discriminating fractures. This newly proposed TBS threshold combined with a BMD T-score of -2.5 or less demonstrated a greater area under receiver operating characteristic curve in identifying patients with osteoporotic fractures than the BMD threshold alone (p value = 0.003).

Conclusion

The reduction in TBS was associated with an osteoporotic fracture in postmenopausal RA patients receiving glucocorticoids. Combining TBS and BMD in these patients incrementally improves fracture risk discrimination and may serve as a supplementary tool in identifying patients at greatest risk of osteoporotic fracture.

Trabecular Bone Score Improves Early After Successful Kidney Transplantation Irrespective of Antiresorptive Therapy and Changes in Bone Mineral Density

Background

Trabecular bone score (TBS) is a new tool to assess trabecular bone microarchitecture based on standard dual-energy x-ray absorptiometry (DXA) of lumbar spine images. TBS may be important to assess bone quality and fracture susceptibility in kidney transplant recipients (KTRs). This study aimed to investigate the effect of different bone therapies on TBS in KTRs.

Methods

We reanalyzed DXA scans to assess TBS in 121 de novo KTRs at baseline, 10 wk, and 1 y. This cohort, between 2007 and 2009, participated in a randomized, placebo-controlled trial evaluating the effect of ibandronate versus placebo in addition to vitamin D and calcium.

Results

Although bone mineral density (BMD) Z scores showed a subtle decrease in the first weeks, TBS Z scores increased from baseline to 10 wk for both treatment groups, followed by a slight decline at 12 mo. When comparing treatment groups and adjusting for baseline TBS, there were no differences found in TBS at 12 mo (P = 0.419). Correlation between TBS and BMD at baseline was weak (Spearman's ρ = 0.234, P = 0.010), and change in TBS was not correlated with changes in lumbar spine BMD in either of the groups (ρ = 0.003, P = 0.973).

Conclusions

Treatment with ibandronate or vitamin D and calcium did not affect bone quality as measured by TBS in de novo KTRs, but TBS increased early, irrespective of intervention. Changes in TBS and BMD during the study period were not correlated, indicating that these measurements reflect different aspects of bone integrity. TBS may complement BMD assessment in identifying KTRs with a high fracture risk.

Evaluation of Clinical and Laboratory Factors Affecting Bone Mineral Density Measurements in Patients with Kidney Transplant

Histological evidence of osteodystrophy and osteopenia is encountered in most patients who have undergone successful renal transplantation. Renal transplantation may be beneficial for correcting uremia-related problems in end-stage renal disease patients; however, its benefit is limited in bone metabolism disorders. The present study aims to evaluate bone mass measurements and investigate the influencing factors in patients with renal transplant. One hundred and eighteen patients (83 males and 35 females) with a mean age of 40.2 ± 11.8 yr (range 20-67) were included in the present study. The laboratory and the clinical data of the patients were retrospectively analyzed. The association between bone mineral density (BMD) measurements and the demographic characteristics of the patients, serum creatinine, parathormone, calcium, phosphorous, alkaline phosphatase, 25-hydroxyvitamin D and the glomerular filtration rate were evaluated. Of the patients, 23.7% (n =28) had normal, 48.3% (n = 57) had osteopenic and 28% (n = 33) had osteoporotic BMD values. A significant positive correlation was determined between the body mass index (BMI) and the BMD measurement results (p = 0.001; r = 0.385). A negative correlation was determined between the BMD values and the serum parathormone (p = 0.012; r = -0.237). BMD values were significantly lower in the group that had not received mammalian target of rapamycin (mTOR) inhibitor (p = 0.026). Conclusion: BMI values, mTOR inhibitor treatment and serum parathormone levels had an effect on the BMD measurement values.

Secondary Osteoporosis

Osteoporosis is a global public health problem, with fractures contributing to significant morbidity and mortality. Although postmenopausal osteoporosis is most common, up to 30% of postmenopausal women, > 50% of premenopausal women, and between 50% and 80% of men have secondary osteoporosis. Exclusion of secondary causes is important, as treatment of such patients often commences by treating the underlying condition. These are varied but often neglected, ranging from endocrine to chronic inflammatory and genetic conditions. General screening is recommended for all patients with osteoporosis, with advanced investigations reserved for premenopausal women and men aged < 50 years, for older patients in whom classical risk factors for osteoporosis are absent, and for all patients with the lowest bone mass (Z-score ≤ -2). The response of secondary osteoporosis to conventional anti-osteoporosis therapy may be inadequate if the underlying condition is unrecognized and untreated. Bone densitometry, using dual-energy x-ray absorptiometry, may underestimate fracture risk in some chronic diseases, including glucocorticoid-induced osteoporosis, type 2 diabetes, and obesity, and may overestimate fracture risk in others (eg, Turner syndrome). FRAX and trabecular bone score may provide additional information regarding fracture risk in secondary osteoporosis, but their use is limited to adults aged ≥ 40 years and ≥ 50 years, respectively. In addition, FRAX requires adjustment in some chronic conditions, such as glucocorticoid use, type 2 diabetes, and HIV. In most conditions, evidence for antiresorptive or anabolic therapy is limited to increases in bone mass. Current osteoporosis management guidelines also neglect secondary osteoporosis and these existing evidence gaps are discussed.

Fibroblast Growth Factor 23 and Osteoporosis: Evidence from Bench to Bedside

Osteoporosis is a chronic debilitating disease caused by imbalanced bone remodeling processes that impair the structural integrity of bone. Over the last ten years, the association between fibroblast growth factor 23 (FGF23) and osteoporosis has been studied in both pre-clinical and clinical investigations. FGF23 is a bone-derived endocrine factor that regulates mineral homeostasis via the fibroblast growth factor receptors (FGFRs)/αKlotho complex. These receptors are expressed in kidney and the parathyroid gland. Preclinical studies have supported the link between the local actions of FGF23 on the bone remodeling processes. In addition, clinical evidence regarding the effects of FGF23 on bone mass and fragility fractures suggest potential diagnostic and prognostic applications of FGF23 in clinical contexts, particularly in elderly and patients with chronic kidney disease. However, inconsistent findings exist and there are areas of uncertainty requiring exploration. This review comprehensively summarizes and discusses preclinical and clinical reports on the roles of FGF23 on osteoporosis, with an emphasis on the local action, as opposed to the systemic action, of FGF23 on the bone. Current gaps in knowledge and future research directions are also suggested to encourage further rigorous research in this important field.

Utility of Trabecular Bone Score (TBS) in Bone Quality and Fracture Risk Assessment in Patients on Maintenance Dialysis

Maintenance dialysis is associated with almost universal changes in bone metabolism collectively known as chronic kidney disease—mineral and bone disorder (CKD-MBD). These are accompanied in various proportions by bone loss and altered bone quality that led to an increased risk of fracture. Osteoporosis, age-related or postmenopausal, a condition that often coexists with CKD, is also a leading cause of fracture. Dual-energy X-ray densitometry (DXA) is the main tool for assessing the bone quantity and bone loss and the associated fracture risk. It has been validated in both CKD-MBD and osteoporosis. Trabecular bone score (TBS) is a DXA-derived algorithm for the evaluation of bone microarchitecture, and its clinical value has been repeatedly demonstrated in large cohorts of osteoporotic patients. However, its utility in patients on maintenance dialysis has not been conclusively shown. Published studies showed a lower TBS score and implicitly an altered bone microarchitecture in patients on maintenance dialysis, even after adjusting for various variables. Moreover, FRAX-based fracture risk is higher after adjusting for TBS, showing promise on an algorithm better estimating the clinical fracture risk in dialysis patients. However, TBS has not been demonstrated to independently predict clinical fractures in prospective studies on dialysis patients. Also, aortic calcifications and altered fluid balance could significantly affect TBS score and could hamper the widespread clinical use in patients on maintenance dialysis. In this mini-review, we focus on the benefits and pitfalls of TBS in the management of CKD-MBD and fracture risk assessment in patients on maintenance dialysis.

Fibroblast Growth Factor 23 and Klotho Are Associated With Trabecular Bone Score but Not Bone Mineral Density in the Early Stages of Chronic Kidney Disease: Results of the Cross-Sectional Study

This study evaluates bone mineral density (BMD) and trabecular bone score (TBS) in relationship with new markers of chronic kidney disease (CKD), fibroblast growth factor 23 (FGF23), and klotho. The patients in this cross-sectional study were divided as follows: group A -patients in stages G1-3; group B -patients in stages G4 - 5 according to KDIGO. Plasma levels of soluble klotho and FGF23 were determined by ELISA. Bone mineral density (BMD) and trabecular bone score (TBS) were measured. 74 patients with CKD (mean age 68.8 years) were included in the study. Higher levels of FGF23 were observed in group B (N=15) compared to group A (N=59; p=0.001) were observed. FGF23 was higher in group A compared to group B. Significant difference in TBS within the first 3 stages of CKD was observed (mean TBS in G1=1.375 vs. G2=1.340 vs. G3a=1.24; p<0.05) and negative correlation of FGF23 and TBS (R=-0.33; p=0.05) and positive correlation between klotho and TBS (R=0.419; p=0.04) was observed. This study confirmed that FGF23 and klotho are associated with TBS, but TBS reflects a decrease in kidney function only in the first 3 stages of CKD. Thus, FGF23 and klotho together with TBS are promising markers of early trabecular bone impairment in CKD.

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.

Circulating microRNAs Related to Bone Metabolism in HIV-Associated Bone Loss

The pathophysiology of human immunodeficiency virus (HIV)-associated bone loss is complex and to date largely unknown. In this study, we investigated serum expression of microRNAS (miRNAs) linked to bone metabolism in HIV-associated bone loss. This was a case-control study. Thirty male individuals with HIV infection (HIV+) and osteoporosis/osteopenia (HIV+/OP+) (cases) and 30 age-matched male HIV+ individuals with normal bone mass (HIV+/OP-) (controls) were included in the analysis. Thirty male individuals matched for age without HIV infection (HIV-), were also included as second controls. The selected panel of miRNAs was as follows: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3p; hsa-miRNA-124-3p; hsa-miRNA-33a-5p; and hsa-miRNA-133a-3p. Within the cohort of HIV+ individuals, relative serum expression of miRNA-21-5p and miRNA-23a-3p was significantly lower (p < 0.001) while the expression of miRNA-24-2-5p was significantly higher (p = 0.030) in HIV+/OP+ compared to HIV+/OP-. Expression of miRNA-21-5p demonstrated a sensitivity of 84.6% and a specificity of 66.7 in distinguishing HIV+/OP+ individuals. Expression of circulating miRNAs related to bone metabolism; miRNA-23a-3p, miRNA-24-2-5p, and miRNA-21-5p is significantly altered in HIV+OP+ individuals, in line with data on other causes of osteoporosis, suggesting a common pattern of circulating miRNAs independent of the underlying cause.

Is Preptin a New Bone Metabolism Parameter in Hemodialysis Patients?

BACKGROUND

Preptin is a bone-anabolic pancreatic peptide hormone. Its role in bone metabolism has been studied in rats and in patients with diabetes, but its levels and significance in bone metabolism in hemodialyzed (HD) patients is unknown.

METHODS

The relationships between preptin and anthropometric and biochemical parameters related to bone metabolism were studied in 73 patients on chronic hemodialysis (48 males, 25 females; mean age of 57 years; HD vintage of 69.7 months). Of these subjects, 36 patients had diabetes or impaired glucose tolerance (DM/IGT), and 37 patients had normal glucose tolerance (NGT). Dual-energy X-ray absorptiometry of the femoral neck and lumbar spine were also performed.

RESULTS

No differences were observed in preptin levels between DM/IGT and NGT HD patients. Preptin was positively correlated with HD vintage (r = 0.312, p = 0.007). Negative correlations between preptin and bone mineral density (BMD), T-score, and Z-score in the lumbar spine (L2-L4) were observed (r = -0.319, p = 0.009; r = -0.341, p = 0.005; r = -0.375, p = 0.002). Preptin was positively correlated with parathormone (PTH) levels (r = 0.379, p < 0.001) and osteocalcin levels (r = 0.262, p = 0.027).

CONCLUSIONS

The results indicate that preptin may reflect on bone and mineral metabolism disturbances seen in HD patients. The significant correlation of preptin with PTH and osteocalcin suggests that preptin may be important in indirect measurement of bone turnover in HD patients.

Expression of Circulating MicroRNAs Linked to Bone Metabolism in Chronic Kidney Disease-Mineral and Bone Disorder

The pathophysiology of chronic kidney disease-mineral and bone disorder (CKD-MBD) is complex and multifactorial. Recent studies have identified a link between microRNAs (miRNAs) and bone loss. In this study, we investigated the expression of miRNAs in CKD-MBD. In this case-control study, we included thirty patients with CKD-MBD (cases) and 30 age- and gender-matched healthy individuals (controls). Bone mineral density (BMD) and trabecular bone score (TBS) evaluation was performed with dual X-ray absorptiometry. The selected panel of miRNAs included: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3; hsa-miRNA-124-3p; hsa-miRNA-2861. The majority of cases had low BMD values. The relative expression of miRNA-21-5p was 15 times lower [fold regulation (FR): -14.7 ± 8.1, p = 0.034), miRNA-124-3p, 6 times lower (FR: -5.9 ± 4, p = 0.005), and miRNA-23a-3p, 4 times lower (FR: -3.8 ± 2.0, p = 0.036) in cases compared to controls. MiRNA-23a-3p was significantly and inversely correlated with TBS, adjusted for calcium metabolism and BMD values (beta = -0.221, p = 0.003, 95% CI -0.360, -0,081) in cases. In a receiver operating characteristic (ROC) analysis, expression of miRNA-124-3p demonstrated 78% sensitivity and 83% specificity in identifying CKD patents with osteoporosis. Serum expression of miRNAs related to osteoblasts (miRNA-23a-3p) and osteoclasts (miRNA-21-5p, miRNA-124-3p) is significantly altered in patients with CKD-MBD.

Trabecular bone score may indicate chronic kidney disease-mineral and bone disorder (CKD-MBD) phenotypes in hemodialysis patients: a prospective observational study

BACKGROUND

In the general population, the trabecular bone score (TBS) represents the bone microarchitecture and predicts fracture risk independent of bone mineral density (BMD). A few studies reported that TBS is significantly reduced in dialysis patients. Chronic kidney disease-mineral and bone disorder (CKD-MBD) are accompanied by increased fracture risk, cardiovascular morbidity, and mortality. We investigated whether TBS is associated with comorbidity related to CKD-MBD or frailty in hemodialysis patients.

METHODS

In this prospective observational study, TBS was obtained using the TBS iNsight software program (Med-Imaps) with BMD dual energy x-ray absorptiometry (DXA) images (L1-L4) from prevalent hemodialysis patients. A Tilburg frailty indicator was used to evaluate frailty, and hand grip strength and bio-impedance (InBody) were measured. A patient-generated subjective global assessment (PG-SGA) was used for nutritional assessment. The history of cardiovascular events (CVE) and demographic, clinical, laboratory, and biomarker data were collated. We then followed up patients for the occurrence of CKD-MBD related complications.

RESULTS

We enrolled 57 patients in total. The mean age was 56.8 ± 15.9 years (50.9% female). Prevalence of Diabetes mellitus (DM) was 40.4% and CVE was 36.8%. Mean TBS was 1.44 ± 0.10. TBS significantly reduced in the CVE group (1.38 ± 0.08 vs. 1.48 ± 0.10, p <  0.001). Multivariable regression analysis was conducted adjusting for age, sex, dialysis vintage, DM, CVE, albumin, intact parathyroid hormone, fibroblast growth factor 23, handgrip strength, and phosphate binder dose. Age (ß = - 0.030; p = 0.001) and CVE (ß = - 0.055; p = 0.024) were significant predictors of TBS. During the follow up period after TBS measurements (about 20 months), four deaths, seven incident fractures, and six new onset CVE were recorded. Lower TBS was associated with mortality (p = 0.049) or new onset fracture (p = 0.007, by log-rank test).

CONCLUSION

Lower TBS was independently associated with increased age and CVE prevalence in hemodialysis patients. Mortality and fracture incidence were significantly higher in patients with lower TBS values. These findings suggest that TBS may indicate a phenotype of frailty and also a CKD-MBD phenotype reciprocal to CVE.

Bone turnover correlates with bone quantity but not bone microarchitecture in chronic hemodialysis

INTRODUCTION

In chronic hemodialysis, high-turnover bone disease was associated with decreased bone mineral density (BMD), poor bone quality (chemical and structural), and increased fracture risk. Our aim was to correlate bone turnover markers (BTMs) with bone microarchitecture measured by trabecular bone score (TBS) before and after correction for BMD.

MATERIALS AND METHODS

We measured lumbar spine (LS), femoral neck, and 1/3 radius BMD and LS TBS by dual X-ray absorptiometry in 81 patients on permanent hemodialysis. Bone turnover was assessed using serum parathyroid hormone, osteocalcin, C-terminal crosslaps of type 1 collagen, procollagen 1 N-terminal propeptide (P1NP), and alkaline phosphatase (ALP). No patient had any partial or total parathyroidectomy and no previous or current treatment with anti-osteoporotic drugs.

RESULTS

All BTMs correlated significantly with each other. Univariate regressions showed significant negative correlations between BTMs and BMD (best r = - 0.53, between P1NP and 1/3 radius Z-score) or BTMs and TBS (best r = - 0.27, p < 0.05 between ALP and TBS T-score). TBS correlated significantly with BMD at all three sites (best r = 0.5, between LS BMD and TBS T-score). Multivariate regression showed that TBS, crude or adjusted, correlated with LS BMD. No model retained any of the BTMs as independent variables due to the better prediction of BMD and multicollinearity.

CONCLUSION

We showed a progressively impaired bone microarchitecture with increasing bone turnover in chronic hemodialysis. However, this correlation is no longer present when controlling for bone mass. This suggests that impaired bone microarchitecture and increased fracture risk are dependent upon factors other than high bone turnover.

New Developments in Fracture Risk Assessment for Current Osteoporosis Reports

PURPOSE OF REVIEW

Identifying individuals at high fracture risk can be used to target those likely to derive the greatest benefit from treatment. This narrative review examines recent developments in using specific risk factors used to assess fracture risk, with a focus on publications in the last 3 years.

RECENT FINDINGS

There is expanding evidence for the recognition of individual clinical risk factors and clinical use of composite scores in the general population. Unfortunately, enthusiasm is dampened by three pragmatic randomized trials that raise questions about the effectiveness of widespread population screening using clinical fracture prediction tools given suboptimal participation and adherence. There have been refinements in risk assessment in special populations: men, patients with diabetes, and secondary causes of osteoporosis. New evidence supports the value of vertebral fracture assessment (VFA), high resolution peripheral quantitative CT (HR-pQCT), opportunistic screening using CT, skeletal strength assessment with finite element analysis (FEA), and trabecular bone score (TBS). The last 3 years have seen important developments in the area of fracture risk assessment, both in the research setting and translation to clinical practice. The next challenge will be incorporating these advances into routine work flows that can improve the identification of high risk individuals at the population level and meaningfully impact the ongoing crisis in osteoporosis management.

Loss of bone mineral density and trabecular bone score in elderly hemodialysis patients: a 2-year follow-up, prospective, single-centre study

BACKGROUND

Low bone mineral density (BMD) and trabecular bone score (TBS) are established risk factors for fractures even in hemodialysis population and they seem to be significantly lower in comparison with general population. The aim of our study was to describe 2-year loss of BMD and TBS and their predictors in hemodialysis patients.

METHODS

From 59 non-selected patients (mean age 67.6 ± 13.1 years) from one dialysis centre, treated with hemodiafiltration (HDF), clinical and laboratory characteristics were obtained and densitometry examinations (with BMD and TBS results) were performed initially and at the end of 2-year follow-up.

RESULTS

Two-year decrease in BMD of lumbar spine reached 4.1% (ns), of proximal femur 9.1% (p = 0.004), and of femoral neck 1.3% (ns). In the co-educated cohort, BMD decrease in all the sites correlated significantly with age and only the change of BMD of lumbar spine was negatively associated with serum calcium (r = - 0.39; p = 0.04) and dialysis vintage (r = - 0.387; p = 0.062), no other predictors of BMD loss were identified. Some predictors of BMD loss were identified with regard to gender. TBS decrease was 0.05 (3.9%; p = 0.03), and similarly, it was not predicted by any of selected parameters. No differences in BMD changes or TBS were observed between the patients with and without fractures.

CONCLUSIONS

In patients with HDF, significant BMD and TBS annual losses were observed, and they were associated only with age and (in BMD of lumbar spine) with serum calcium and dialysis vintage.

Factors associated with low trabecular bone scores in patients with end-stage kidney disease

The trabecular bone score (TBS) is a textural index that indirectly assesses bone trabecular microarchitecture using lumbar spine images obtained by dual-energy X-ray absorptiometry (DXA). This study compared the TBS of patients with end-stage kidney disease (ESKD) with that of matched controls to identify risk factors associated with a low TBS. TBS and bone mineral density (BMD) were assessed in ESKD patients (n = 76) and age- and sex-matched control subjects (n = 76) using DXA. The TBS of both groups was then compared, and risk factors associated with a low TBS (defined as ≤ 1.31) were evaluated. The mean TBS in the ESKD group was significantly lower than that in the control group (1.34 ± 0.15 vs. 1.43 ± 0.08, respectively; p < 0.001). More subjects in the ESKD group had a low TBS [34.2% (ESRD) vs. 5.3% (controls); p < 0.001]. The TBS was negatively correlated with age, alkaline phosphatase and C-reactive protein levels, and dialysis vintage, and positively correlated with BMD at the lumbar spine, femoral neck, and hip. Multivariate analysis identified lower estimated glomerular filtration rate and increased C-reactive protein levels as being significantly associated with a low TBS. In conclusion, ESKD patients had abnormal bone microarchitecture (as assessed by the TBS). The TBS was positively correlated with BMD. Renal function and inflammatory marker levels were independently associated with a low TBS. Thus, TBS may be a useful clinical tool for assessing cancellous bone connectivity in ESKD patients.

Osteoporosis complicating some inborn or acquired diseases

Osteoporosis in chronic diseases is very frequent and pathogenetically varied. It complicates the course of the underlying disease by the occurrence of fractures, which aggravate the quality of life and increase the mortality of patients from the underlying disease. The secondary deterioration of bone quality in chronic diseases, such as diabetes of type 1 and type 2 and/or other endocrine and metabolic disorders, as well as inflammatory diseases, including rheumatoid arthritis - are mostly associated with structural changes to collagen, altered bone turnover, increased cortical porosity and damage to the trabecular and cortical microarchitecture. Mechanisms of development of osteoporosis in some inborn or acquired disorders are discussed.

Chronic hemodialysis is associated with lower trabecular bone score, independent of bone mineral density: a case-control study

We measured trabecular bone score (TBS) in 98 patients on permanent hemodialysis (HD) and 98 subjects with similar bone mineral density and normal kidney function. TBS was significantly lower in HD patients, indicating deteriorated bone microarchitecture, independent of bone mass. This might partially explain the increased fracture risk in HD.

PURPOSE

In the general population, trabecular bone score (TBS) was shown to predict fracture independent of bone mineral density (BMD). In end-stage renal disease patients on hemodialysis (HD), the value of TBS is beyond that of BMD in currently unclear. Our aim was to assess lumbar spine (LS) TBS in HD patients compared with subjects with normal kidney function matched for age, sex, and LS BMD.

METHODS

We assessed TBS and LS and femoral neck (FN) BMD in 98 patient on permanent HD (42.8% males; mean age 57.5 ± 11.3 years; dialysis vintage 5.5 ± 3.8 years) and 98 control subjects (glomerular filtration rate > 60 mL/min) using DXA. We simultaneously controlled for sex, age (± 3 years), and LS BMD (± 0.03 g/cm²).

RESULTS

HD patients had significantly lower LS TBS (0.07 [95% CI 0.03-0.1]; p = 0.0004), TBS T-score (0.83 SD [95% CI 0.42-1.24]; p = 0.0001)) and TBS Z-score (0.81 SD [95% CI 0.41-1.20]; p = 0.0001) than matched controls. TBS significantly correlated with LS BMD in both HD patients (r = 0.382; p = 0.001) and controls (r = 0.36; p = 0.002). The two regression lines had similar slopes (0.3 vs. 0.28; p = 0.84) with different intercepts (0.88 vs. 0.98). TBS adjustment significantly increased the 10-year fracture risk from 3.7 to 5.3 for major osteoporotic fracture and from 0.9 to 1.5 for hip fracture.

CONCLUSIONS

HD patients have lower TBS than controls matched for LS BMD, indicating altered bone microarchitecture. Also, the magnitude of TBS reduction in HD patients is constant at any LS BMD. Adjustment for TBS partially corrects the absolute 10-year fracture risk.

The trabecular bone score: Relationships with trabecular and cortical microarchitecture measured by HR-pQCT and histomorphometry in patients with chronic kidney disease

The trabecular bone score (TBS) is a novel tool using grayscale variograms of the lumbar spine bone mineral density (BMD) to assess trabecular bone microarchitecture. Studies in patients with chronic kidney disease (CKD) suggest it may be helpful in assessing fracture risk. However, TBS has not been validated as a measure of trabecular architecture against transiliac bone biopsy with histomorphometry in CKD patients. We hypothesized that TBS would reflect trabecular architecture at the iliac crest in CKD patients. We obtained tetracycline double labeled transiliac crest bone biopsy, areal BMD of the spine, total hip, femoral neck (FN) and spine TBS by dual energy X-ray absorptiometry (DXA), and cortical and trabecular volumetric density and microarchitecture by high resolution peripheral quantitative computed tomography (HR-pQCT) in CKD patients from two centers: twenty-two patients from Columbia University Medical Center, USA and thirty patients from Hospital das Clinicas - Universidade de São Paulo, Brazil. Two patients were excluded for outlier status. Univariate and multivariate relationships between TBS and measures from DXA, HR-pQCT and histomorphometry were determined. Patients were 50.2 ± 15.8 years old, 23 (46%) were men, and 33 (66%) were on dialysis. TBS was <1.31 in 21 (42%) patients and 22%, 14% and 10% had T-scores ≤ -2.5 at spine, FN and total hip respectively. In univariate regression, TBS was significantly associated with trabecular bone volume (BV/TV), trabecular width (Tb.Wi), trabecular spacing, cortical width but not with trabecular number or cortical porosity. FN Z-score and height were also associated with cancellous BV/TV and Tb.Wi, In multivariate analysis, TBS remained an independent predictor of BV/TV and Tb.Wi. There were no relationships between TBS and dynamic parameters from histomorphometry. These data suggest that TBS reflected trabecular microarchitecture and cortical width measured by bone biopsy in CKD patients. Future studies should address its utility in the identification of CKD patients who may benefit from fracture prevention strategies.

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.

Aortic vascular calcification is inversely associated with the trabecular bone score in patients receiving dialysis

INTRODUCTION

Progressive chronic kidney disease (CKD) confers a marked increase in risk for vascular calcification, cardiovascular disease, fracture and mortality, with likely contributing factors including dysregulated bone metabolism and mineral homeostasis. In general population studies, increased vascular calcification is directly related to mortality and inversely related to bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA). In patients with CKD, abnormalities in turnover, mineralization and bone volume reduce the ability of DXA to predict fracture. The trabecular bone score (TBS) obtained from lumbar spine DXA images, provides a surrogate measure of microarchitectural integrity not captured by BMD. This study aimed to examine the association of the TBS to prevalent abdominal aortic calcification (AAC) in patients with CKD receiving dialysis.

METHODS

We performed a cross-sectional study of dialysis patients awaiting transplantation. All patients underwent laboratory testing, lateral spinal radiographs including the abdominal aorta, DXA imaging and TBS assessment. AAC scores were determined using the Kauppila method. Correlations and linear regression models were used to determine predictors of AAC scores.

RESULTS

146 patients (60% male, mean age 48 ± 13 years) were included, of whom 49% had prevalent calcification with an AAC score ≥ 1. Of those with calcification, the mean AAC score was 7 ± 5.5 and 42 patients had scores ≥ 6, considered to indicate severe AAC. TBS values corresponding to intermediate or high risk for fracture (<1.31) were present in 35% of patients. TBS values correlated inversely to AAC scores (β = -0.206, p = 0.013) and remained significant in multivariable linear regression, adjusting for age, BMI and time on dialysis (-0.160, p = 0.031). There was no significant correlation of AAC scores to any BMD parameter.

CONCLUSION

There is a high prevalence of AAC in relatively young dialysis patients awaiting transplantation and their AAC scores are inversely related to the TBS but not to DXA-derived BMD parameters. In patients with CKD on dialysis, TBS assessment reflects microarchitectural abnormalities of bone not captured by DXA. The inverse relationship of TBS to vascular calcification may provide insights into bone-vascular interactions in CKD.

The trabecular bone score is associated with bone mineral density, markers of bone turnover and prevalent fracture in patients with end stage kidney disease

Fracture risk increases in end-stage kidney disease (ESKD), but bone mineral density (BMD) measurement is less predictive of risk than in the general population. In this study of patients with ESKD, a lower trabecular bone score (TBS), indicative of microarchitectural deterioration, was associated with higher bone turnover markers and prevalent non-vertebral fracture.

INTRODUCTION

Declining renal function carries increased fracture risks, but BMD is less predictive of fracture for dialysis patients than the general population. The TBS, obtained from lumbar spine dual-energy X-ray absorptiometry (DXA) images, provides information on microarchitectural integrity not captured by BMD. The aim of this study was to assess associations of the TBS to clinical, DXA, radiological, and laboratory measures in patients with ESKD undergoing kidney and simultaneous pancreas kidney (SPK) transplantation.

METHODS

A total of 147 patients with ESKD underwent pre-transplant laboratory testing, DXA, lateral spine X-ray, and structured history within 4 weeks of transplantation. Associations of the TBS to demographic data, prevalent fracture, BMD, and laboratory variables were assessed.

RESULTS

Of 147 patients (60% male, mean age 48 ± 13 years), 36% had diabetes mellitus (DM) and 54 patients had fractures: 21 prevalent vertebral fractures only, 22 non-vertebral fractures only, and 11 had both. The mean TBS (1.345 ± 0.125) was lower in patients undergoing SPK than kidney-only transplants (1.292 vs. 1.364, p = 0.001). The TBS correlated to spine and total hip BMD, body mass index and inversely to parathyroid hormone, alkaline phosphatase and procollagen 1 N-propeptide. By multivariable logistic regression, lower TBS was significantly associated to prior non-vertebral fracture (p = 0.026).

CONCLUSIONS

A lower TBS, suggestive of increased microarchitectural damage, was associated with type 1 DM, markers of higher bone turnover, and prevalent fracture. These data support the need for prospective studies to evaluate whether TBS inclusion improves fracture prediction in patients with ESKD.

Review on the Utility of Trabecular Bone Score, a Surrogate of Bone Micro-architecture, in the Chronic Kidney Disease Spectrum and in Kidney Transplant Recipients

Chronic kidney disease (CKD) is defined as abnormalities of kidney structure or function, present for >3 months, with implications for, among others, bone health. Advanced stages of CKD have an increased risk of fragility fractures. Trabecular bone score (TBS) is a relatively new gray-level textural parameter, which provides information on bone microarchitecture and has been shown to be a good predictor of fragility fractures independently of bone density and clinical risk factors. We aimed to review the scientific literature on TBS and its utility along the CKD spectrum and in kidney transplant recipients. In total, eight articles had investigated this topic: one article in patients with reduced kidney function, two in patients on hemodialysis, and five in kidney transplant recipients. In general, all the studies had shown an association between lower values of TBS and reduced kidney function; or lower TBS values among the hemodialysis or kidney transplant patients compared to healthy controls. Moreover, TBS was shown to be a good and independent predictor of fragility fractures in patients with CKD or who underwent kidney transplantation. TBS postulates itself as a valuable marker to be used in clinical practice as an assessor of bone microarchitecture and fracture risk predictor in these specific populations. However, evidence is to some extent limited and larger follow-up case-control studies would help to further investigate the TBS utility in the management of bone health damage and increased fracture risk in patients with CKD or kidney transplant.