Low bone mineral density and fractures in long-term hemodialysis patients: a meta-analysis

Cortical bone mechanical properties are altered in an animal model of progressive chronic kidney disease

Chronic kidney disease (CKD), which leads tocortical bone loss and increasedporosity,increases therisk of fracture. Animal models have confirmed that these changes compromise whole bone mechanical properties. Estimates from whole bone testing suggest that material properties are negatively affected, though tissue-level assessmentshavenot been conducted. Therefore, the goal of the present study was to examine changes in cortical bone at different length scales using a rat model with theprogressive development of CKD. At 30 weeks of age (∼75% reduction in kidney function), skeletally mature male Cy/+ rats were compared to their normal littermates. Cortical bone material propertieswere assessed with reference point indentation (RPI), atomic force microscopy (AFM), Raman spectroscopy,and high performance liquid chromatography (HPLC). Bones from animals with CKD had higher (+18%) indentation distance increase and first cycle energy dissipation (+8%) as measured by RPI.AFM indentation revealed a broader distribution of elastic modulus values in CKD animals witha greater proportion of both higher and lower modulus values compared to normal controls. Yet, tissue composition, collagen morphology, and collagen cross-linking fail to account for these differences. Though the specific skeletal tissue alterations responsible for these mechanical differences remain unclear, these results indicate that cortical bone material properties are altered in these animals and may contribute to the increased fracture risk associated with CKD.

Fragility fractures and osteoporosis in CKD: pathophysiology and diagnostic methods

Both chronic kidney disease (CKD) and osteoporosis are major public health problems associated with an aging population. Osteoporosis is characterized by reduced bone mineral density, while CKD results in qualitative changes in bone structure; both conditions increase the predisposition to fragility fractures. There is a significant coprevalence of osteoporotic fractures and CKD, particularly in the elderly population. Not only is the risk of fracture higher in the CKD population, but clinical outcomes are significantly worse, with substantial health care costs. Management of osteoporosis in the CKD population is particularly complex given the impact of renal osteodystrophy on bone quality and the limited safety and hard outcome data for current therapy in patients with severe CKD or on dialysis therapy. In this review, we discuss the pathophysiology of osteoporosis, the impact of CKD on bone strength, and the role of novel imaging techniques and biomarkers in predicting underlying renal osteodystrophy on bone histomorphometry in the context of CKD.

The clinical utility of FRAX to discriminate fracture status in men and women with chronic kidney disease

We assessed the ability of the World Health Organization's fracture risk assessment tool (FRAX), bone mineral density (BMD), and age to discriminate fracture status in adults with pre-dialysis chronic kidney disease (CKD). In adults with CKD, FRAX was able to discriminate fracture status but performed no better than BMD alone.

INTRODUCTION

Patients with CKD are at increased risk for fracture but the best method to assess fracture risk is not known.

METHODS

We assessed the ability of the World Health Organization's FRAX, compared with BMD at the femoral neck (FN), and age to discriminate fracture status (prevalent clinical nonspine and/or morphometric vertebral) in men and women, 18 years and older with pre-dialysis CKD. Results are presented as area under receiver operator characteristic curves (AUC) with 95% confidence intervals (CI).

RESULTS

We enrolled 353 subjects; mean age was 65 ± 14 years; weight was 79 ± 18 kg, and estimated glomerular filtration rate was 28 ml/min/1.73 m(2). About one third of the subjects had a prevalent clinical nonspine and/or morphometric vertebral fracture. FRAX was able to discriminate among those with prevalent clinical nonspine fractures (AUC, 0.72; 95% CI, 0.65-0.78), morphometric vertebral fractures (AUC, 0.66; 95% CI, 0.59-0.73), and any fracture (AUC, 0.71; 95% CI, 0.65-0.77). The discriminative ability of BMD at the FN alone was similar to FRAX for morphometric vertebral and any fractures; FRAX performed better than BMD for prevalent clinical nonspine fractures (AUC for BMD alone, 0.66; 95% CI, 0.60-0.73). Compared to FRAX, the AUC for age alone was lower for all fracture types.

CONCLUSIONS

Among men and women with CKD, FRAX is able to discriminate fracture status but performs no better than BMD alone.

Incidence and risk factors for hip fractures in dialysis patients

This study described the incidence of hip fractures, associated diseases, and related costs generated in dialysis versus non-dialysis patients.

INTRODUCTION

Skeletal fractures are a great concern in chronic kidney disease patients and, in particular, hip fractures that enhance the mortality. We aimed to accurately determine the incidence of hip fractures and associated diseases and to calculate the costs generated in dialysis patients.

METHODS

We obtained data from the 2010 French National Hospital Database. We first extracted the hospital stays related to hip fractures as a primary diagnosis according to the ICD-10 codes and then the hospitalizations for dialysis. We compared the frequency of comorbidities in both populations.

RESULTS

Among the 88,962 patients who suffered from hip fractures, 362 were on dialysis. The incidence was significantly higher in dialysis patients (x4) compared to non-dialysis patients. Women on dialysis experienced hip fractures at an earlier age than non-dialysis women. Dementia was identified as a major risk factor in the dialysis patients (72 vs. 26%, p < 0.0001). Moreover, diabetes and cardiovascular diseases were comorbidities strongly associated with hip fractures in both gender, but hypertension and malnutrition were observed exclusively in men on dialysis. Mortality rate and length of hospital stay were increased (5 days) in both genders.

CONCLUSION

The incidence of hip fractures is increased in dialysis patients, affecting a larger percentage of men and women on dialysis than in the non-dialysis population and enhancing the financial burden and mortality. Dementia is a major risk factor for hip fractures in dialysis patients in addition to diabetes and cardiovascular diseases.

Accumulated uremic toxins attenuate bone mechanical properties in rats with chronic kidney disease

The prevalence of hip fracture is very high among patients with chronic kidney disease (CKD); however, the reason for this is unclear. We examined the effects of accumulated uremic toxins on bone chemical composition and elastic mechanical properties. Rats underwent thyroparathyroidectomy and progressive partial nephrectomy (TPTx-Nx), and were administered with vehicle or AST-120 to reduce serum indoxyl sulfate (IS) levels. Bone mechanical properties, bone mineral density (BMD), cortical bone chemical composition, and histomorphometry were determined. Storage modulus was reduced in TPTx-Nx rats compared with rats that underwent TPTx alone. BMD and histomorphometric parameters did not differ between the groups. In terms of cortical bone chemical composition, the mineral/matrix ratio and carbonate substitution was increased, whereas crystallinity was decreased in TPTx-Nx rats. The enzymatic crosslink ratio and pentosidine:matrix ratio were increased in TPTx-Nx rats. AST-120 abolished the effects of TPTx-Nx and decreased the serum IS concentration. Stepwise multiple regression analysis revealed that the pentosidine:matrix and mineral:matrix ratios were independent contributors to the storage modulus. In conclusion, the accumulated uremic toxins, including IS, seem to play an important role in deteriorating bone mechanical properties by altering the chemical composition of bone. This mechanism may account for the increased prevalence of hip fracture among patients with CKD.

Uremic osteoporosis

Abnormalities in bone turnover, mineralization, and volume represent one of the three components of chronic kidney disease–related mineral and bone disorder (CKD-MBD). The risk of hip fracture is considerably high, while the risk of spinal compression fracture may not be more elevated among CKD patients than in general population. The relationship between bone fracture and bone mineral density in CKD patients is more complex than in those without kidney disease. An increase in the rate of falls has been reported to be a major cause of high hip fracture risk among CKD patients; however, it certainly is not the only underlying mechanism. Abnormal parathyroid function is not likely to be a major cause of hip fracture among CKD patients. In experimental CKD animals, mechanical elasticity properties of long bones showed an inverse correlation with kidney function. The deterioration of bone elasticity showed a significant correlation with bone biochemical changes. Of note, administration of the oral absorbent AST-120 was capable of preventing both changes. These findings suggest that uremic toxins cause a deterioration of bone material properties, and changes in material properties disturb bone elasticity. This disease concept cannot be considered to be a direct consequence of CKD-MBD. We therefore would like to call it ‘uremic osteoporosis'. This entity may be a major cause of increased hip fracture risk among CKD patients.

Recent advances in the noninvasive diagnosis of renal osteodystrophy

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is the term used to describe a constellation of biochemical abnormalities, bone disturbances that may lead to fractures, and extraskeletal calcification in soft tissues and arteries seen in CKD. This review focuses on the noninvasive diagnosis of renal osteodystrophy, the term used exclusively to define the bone pathology associated with CKD. Transiliac bone biopsy and histomorphometry with double-labeled tetracycline or its derivatives remains the gold standard for diagnosis of renal osteodystrophy. However, histomorphometry provides a 'window' into bone only at a single point in time, and is not clinically practical for studying continuous changes in bone morphology. Furthermore, the etiology of fractures in CKD is multifactorial and not fully explained by histomorphometry findings alone. The propensity of a bone to fracture is determined by bone strength, which is affected by bone mass and bone quality; the latter is a term used to describe the structure and composition of bone. Bone quantity is traditionally assessed by dual X-ray absorptiometry (DXA) and CT-based methods. Bone quality is more difficult to assess noninvasively, but newer techniques are emerging and are described in this review. Ultimately, the optimal diagnostic strategy for renal osteodystrophy may be a combination of multiple imaging techniques and biomarkers that are specific to each gender and race in CKD, with a goal of predicting fracture risk and optimizing therapy.

Temporal trends in fracture rates and postdischarge outcomes among hemodialysis patients

Patients with ESRD have a substantially increased risk of bone fractures, but the burden of fractures has not been sufficiently characterized in this population. Here, we analyzed fracture rates and postdischarge outcomes using Medicare data from hemodialysis patients in the United States between 2000 and 2009. We assessed adjusted quarterly fracture rates (inpatient and outpatient) and consequences of postfracture hospitalization for seven categories of fracture location. Pelvis/hip, vertebral, and lower leg fractures were the most prevalent fracture types. Pelvis/hip fractures declined slightly from 29.6 to 20.6 per 1000 patient-years between early 2000 and late 2009, but the incidence rates for all other fracture types remained relatively constant. Median lengths of stay for the primary fracture hospitalization ranged from 5 days (interquartile range [IQR], 3-9 days) for forearm/wrist fractures to 8 days (IQR, 5-12 days) for femur fractures. The proportion of patients discharged from the primary hospitalization to a skilled-nursing facility ranged from 28% (ribs/sternum) to 47% (pelvis/hip). A negative binomial regression model suggested that patients had an adjusted mean of 3.8-5.2 additional hospitalizations during the year after discharge from the index hospitalization, varying by fracture type, comprising a mean of 33-52 inpatient days. Case-mix-adjusted mortality rates after discharge ranged from 0.43 to 0.91 per patient-year and were highest for vertebral, pelvis/hip, and femur fractures. In conclusion, fractures in the dialysis population are common and are associated with a substantially increased risk for death and hospitalization.

Temporal trends in fracture rates and postdischarge outcomes among hemodialysis patients

Patients with ESRD have a substantially increased risk of bone fractures, but the burden of fractures has not been sufficiently characterized in this population. Here, we analyzed fracture rates and postdischarge outcomes using Medicare data from hemodialysis patients in the United States between 2000 and 2009. We assessed adjusted quarterly fracture rates (inpatient and outpatient) and consequences of postfracture hospitalization for seven categories of fracture location. Pelvis/hip, vertebral, and lower leg fractures were the most prevalent fracture types. Pelvis/hip fractures declined slightly from 29.6 to 20.6 per 1000 patient-years between early 2000 and late 2009, but the incidence rates for all other fracture types remained relatively constant. Median lengths of stay for the primary fracture hospitalization ranged from 5 days (interquartile range [IQR], 3-9 days) for forearm/wrist fractures to 8 days (IQR, 5-12 days) for femur fractures. The proportion of patients discharged from the primary hospitalization to a skilled-nursing facility ranged from 28% (ribs/sternum) to 47% (pelvis/hip). A negative binomial regression model suggested that patients had an adjusted mean of 3.8-5.2 additional hospitalizations during the year after discharge from the index hospitalization, varying by fracture type, comprising a mean of 33-52 inpatient days. Case-mix-adjusted mortality rates after discharge ranged from 0.43 to 0.91 per patient-year and were highest for vertebral, pelvis/hip, and femur fractures. In conclusion, fractures in the dialysis population are common and are associated with a substantially increased risk for death and hospitalization.

Renale osteodystrophie

The incidence of renal osteodystrophy (ROD) increases with deteriorating kidney function, affecting virtually every patient on chronic dialysis treatment. ROD can persist after kidney transplantation and may be aggravated by immunosuppressants, mainly glucocorticoids. Fracture risk, including hip fractures, is markedly elevated in patients with renal disease compared to the general population. Depending on the type of ROD, high or low bone turnover can be found. Because of poor positive and negative predictive values of serological markers of bone turnover and limited technical capabilities of various bone imaging modalities, the only reliable method to correctly classify ROD is the transiliac bone biopsy. Elevated bone turnover can be successfully treated with active vitamin D, cinacalcet, or parathyreoidectomy, but all of these therapies may lead to oversuppression of bone metabolism. Currently, no specific therapy is available for low turnover bone disease. Bisphosphonates can be a therapeutic option for selected patients after renal transplantation.

Obesity and risk of hip fracture in adults: a meta-analysis of prospective cohort studies

Background

Many observational studies assessed the association between obesity and risk of hip fracture in adults, but reported controversial results. Our goal was to evaluate the association between obesity and risk of hip fracture in adults by conducting a meta-analysis of prospective cohort studies.

Methods

Three databases, PubMed, Embase and Web of Science, were searched through May 2012 to identify eligible cohort studies. Either a fixed- or a random-effects model was used to calculate the pooled relative risk (RR) with its 95% confidence interval (95%CI).

Results

Fifteen prospective cohort studies involving a total 3,126,313 participants were finally included into this meta-analysis. Overall, adults with obesity compared with the normal weight group had a significantly decreased risk of hip fracture (RR: 0.66, 95% CI 0.57 to 0.77, P<0.001). Meta-analyses by the adjusted status of RRs also suggested adults with obesity compared with the reference group had a significantly decreased risk of hip fracture (adjusted RR: 0.48, 95% CI 0.39 to 0.58, P<0.001; unadjusted RR: 0.66, 95% CI 0.56 to 0.78, P<0.001). Subgroup analyses by gender suggested individuals with obesity had a significantly decreased risk for developing hip fracture compared with the reference group in both men (RR 0.54, 95% CI 0.48 to 0.60, P<0.001) and women (RR 0.70, 95% CI 0.58 to 0.84, P<0.001). No evidence of publication bias was observed in this meta-analysis.

Conclusions

This meta-analysis of prospective cohort studies suggests that obesity significantly decreases the risk of hip fracture in adults, and obesity is probably a protective factor of hip fracture in adults.

Epidemiological study of orthopedic injuries in hemodialysis patients in Taiwan: a fixed cohort survey, 2004-2008

BACKGROUND

The burden of chronic kidney disease (CKD) is a growing concern worldwide. The prevalence of hemodialysis in Taiwan is the highest in the world, and this may increase the prevalence of orthopedic fractures. The aim of this study was to explore the incidences of various orthopedic injuries and the related risk factors.

METHODS

A nationwide prospective study based on the Taiwan National Health Insurance dataset was conducted during 2004-2008. A total of 82,491 CKD patients were selected as the fixed cohort population. The International Classification of Diseases 9-CM diagnosis codes and treatment codes were identified as the inclusion criteria for orthopedic injury.

RESULTS

A total of 82,491 Taiwanese people with CKD were identified in 2004, and 4915 orthopedic injuries occurred during the 5-year follow-up period. The cumulative incidences of orthopedic injuries were 42.56‰ for lower limb fractures, and 12.93‰, 3.27‰, and 1.64‰ for upper limb fractures, vertebrae fractures, and joint dislocations, respectively. All three types of orthopedic fractures were more common in the oldest age stratum (≥65 years old). In the CKD patients, the risk ratio of osteoporosis was 3.47 (95% confidence interval, 3.10-3.89) for all orthopedic injuries. Patients of advanced age, the female gender, and those with high comorbidity were also at significant risk of sustaining orthopedic fractures.

CONCLUSION

The results from this Taiwanese CKD cohort support the strong influence of aging and osteoporosis on all kinds of orthopedic injuries. The postponing of osteoporosis may need to be taken into consideration for the prevention of orthopedic injury among CKD patients undergoing hemodialysis.

Risk factors for diminished bone mineral density among male hemodialysis patients--a cross-sectional study

This cross-sectional study was performed to characterize the factors affecting bone mass in male hemodialysis subjects. We found that of all the factors analyzed, the strongest correlation was with body mass index. In fact, after adjusting for body weight, the correlations with bone turnover markers and sex hormones were no longer significant.

PURPOSE

Abnormalities in bone and mineral metabolism are commonly seen in patients with end-stage renal disease, reducing bone quality and raising the risk of fracture. This cross-sectional study was performed to characterize risk factors affecting bone mass among male hemodialysis subjects.

METHODS

For this cross-sectional study, we recruited 66 men from three local hemodialysis units. Subjects received dual emission X-ray absorptiometry assessment of three sites (lumbar spine, hip, and distal radius) and the values were correlated with the levels of sex hormones, non-renally excreted bone turnover markers, and mineral metabolism markers.

RESULTS

Subjects were found to have bone mineral density (BMD) reduced predominantly at the distal radius, with Z score < −2 seen in 15.4 % and T score < −2.5 in 21 % of men. Independent predictors of bone density included levels of bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase 5b, which were inversely correlated with the femoral neck Z score. Factors positively associated with an increased Z score included body mass index at all sites and free estradiol levels at the hip and distal radius. Markers of mineral metabolism (e.g., calcium, phosphate, and 25-hydroxyvitamin D) were not correlated with Z scores of any site or with bone turnover markers. After adjusting for body weight, the associations between BMD, sex hormones, and bone turnover markers were no longer significant.

CONCLUSION

We recommend that future studies seeking to assess the factors affecting bone strength among male hemodialysis subjects incorporate a weight-adjusted analysis. Additionally, dialysis-dependent men receiving dual emission X-ray absorptiometry should have the distal radius site added to the standard assessment.

Bone mineral density by DXA and HR pQCT can discriminate fracture status in men and women with stages 3 to 5 chronic kidney disease

Fractures are common in chronic kidney disease (CKD). We determined if bone mineral density testing by dual energy X-ray absorptiometry (DXA) and high resolution peripheral quantitative computed tomography (HR pQCT) could discriminate fracture status in CKD patients. Both tests were able to discriminate fracture status. Further, the addition of HR pQCT measurements to DXA measurements did not improve fracture discrimination.

INTRODUCTION

The optimal method to identify individuals with CKD at high fracture risk is unknown.

METHODS

We determined if bone mineral density (BMD) by DXA and HR pQCT could discriminate fracture status in 211 adult men and women with stages 3 to 5 CKD, attending predialysis clinics in Toronto Canada, using logistic regression. Results are expressed as the odds ratio (OR) of fracture (prevalent vertebral and/or low trauma since age 40 years) per standard deviation decrease in the predictor adjusted for age, weight, sex, and CKD stage. We constructed receiver operating characteristic curves to examine the discriminative ability of BMD measures for fracture.

RESULTS

Most participants were Caucasian men with a mean age of 63.3 ± 15.5 years. There were 77 fractures in 74 participants. Decreases in BMD were associated with increased fracture risk: OR = 1.56 (95% confidence interval (CI), 1.41 to 1.71) for BMD by DXA at the ultradistal radius, and OR = 1.24 (95% CI, 1.12 to 1.36) for cortical area by HR pQCT. Further, while both tests were able to discriminate fracture status, the addition of HR pQCT measures to BMD by DXA did not improve fracture discrimination ability.

CONCLUSIONS

Among CKD patients not yet requiring renal replacement therapy, BMD by DXA is able to discriminate fracture status.

Evaluation of bone microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) in hemodialysis patients

Hemodialyzed patients have decreased bone strength not completely characterized. We evaluated bone microarchitecture in hemodialysis patients and compared it to that of subjects without renal disease by high-resolution peripheral quantitative computed tomography (HR-pQCT). Hemodialysis patients have a marked decreased in cortical density, thickness, and area with significant reduction in trabecular parameters that correlated with the severity of secondary hyperparathyroidism only in women.

INTRODUCTION

Although fracture risk is greatly increased in dialysis patients, the corresponding decreased in bone strength has not been completely characterized.

METHODS

We evaluated volumetric bone mineral density (vBMD) and bone microstructure by HR-pQCT at the distal radius and tibia in 50 hemodialyzed (HD) patients (30 females, mean age 53.2 ± 6 years and 20 males, mean age 59.1 ± 11 years) and 50 sex- and age-matched controls.

RESULTS

At the distal radius HD, women showed a 29% reduction in total and trabecular density and trabecular bone volume fraction (p < 0.0001) compared to controls. Trabecular number was reduced by 25% (p < 0.0001), while trabecular separation was increased by 51%. Cortical thickness (-40%, p < 0.0001) and cortical area (-42%, p < 0.0001) were the parameters most reduced, while compact density was the parameter least reduced (-15%, p < 0.0001). Similar findings were found at the tibia. In HD men, HR-pQCT at the distal radius and tibia showed a reduction in volumetric density and microstructure parameters to a lesser extent than in women. In the hemodialyzed group, cortical thickness at the radius was negatively correlated with age both in women and men. At the distal radius and tibia, we found significant negative correlations between Log iPTH and total alkaline phosphatase with cortical vBMD(r = -0.48, p < 0.01; r = -0.69, p < 0.001), thickness (-0.37, p < 0.05; r = -0.60, p < 0.001), and area ((r = -0.43, p = 0.02; r = -0.65, p < 0.001) but only in women.

CONCLUSION

We conclude that hemodialysis patients have a marked decreased in cortical density, thickness, and area with significant reduction in trabecular parameters that correlated with the severity of secondary hyperparathyroidism only in women.

Bone and kidney disease: diagnostic and therapeutic implications

Fractures are common in patients with chronic kidney disease (CKD), but the diagnosis and treatment of bone disease in CKD are difficult due to the multiple etiologies of bone disease in these patients. Noninvasive imaging, including bone mineral density by dual energy x-ray absorptiometry, can be useful in diagnosing osteoporosis in predialysis CKD; however, consensus on the diagnosis of osteoporosis among those with advanced CKD-particularly stage 5 CKD patients on dialysis-is lacking. Treatments approved for osteoporosis in postmenopausal women may be used in patients with stage 1 to 3 CKD. Furthermore, post-hoc analyses show efficacy and safety of oral bisphosphonates, raloxifene, and denosumab in stage 4 CKD for short-term treatment. However, treatment decisions are more difficult in stage 5 CKD. Bone biopsy may be required, and most treatments, if used, would be off label. Overall, the diagnosis and treatment of bone disease in patients with CKD require further research.

Determination of bone architecture and strength in men and women with stage 5 chronic kidney disease

Fractures are common in men and women with dialysis-dependent chronic kidney disease (stage 5D CKD) and are associated with substantial morbidity and mortality. The clinical utility of dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT), noninvasive measures of bone mass and architecture that reflect fracture risk in healthy men and women, is uncertain in patients with stage 5D CKD. This review will outline the epidemiology and etiology of fractures and will summarize the published data that describe the association between fractures, bone mass, and bone strength in stage 5D CKD. Fracture risk assessment in stage 5D CKD is complicated as the etiology of fractures is multifactorial and includes impairments in bone quantity and quality. Cross-sectional data suggest that bone density by DXA is lower among stage 5D CKD patients with fractures compared with those without, and that this may be particularly true at cortical sites. However, DXA does not capture bone microarchitecture and cannot differentiate between cortical and trabecular bone. Some, but not all studies, that measure cortical and trabecular bone by pQCT in stage 5D CKD, demonstrate a preferential decrease in cortical bone; however, these studies are limited by small sample sizes and cross-sectional study design. No studies have reported on longitudinal relationships between bone architecture, strength, and incident fractures in patients with stage 5D CKD. Further research is needed to identify noninvasive measures of bone strength that can be used for fracture risk assessment in stage 5D CKD.

Bone mineral density and fracture risk in older individuals with CKD

BACKGROUND AND OBJECTIVES

Kidney Disease Improving Global Outcomes guidelines recommend against bone mineral density (BMD) screening in CKD patients with mineral bone disease, due to a lack of association of BMD with fractures in cross-sectional studies in CKD. We assessed whether BMD is associated with fractures in participants with and without CKD in the Health, Aging, and Body Composition study, a prospective study of well functioning older individuals.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Hip BMD was measured by dual-energy x-ray absorptiometry. Osteoporosis was defined as a femoral neck BMD (FNBMD) T score below -2.5 and CKD as an estimated GFR <60 ml/min per 1.73 m(2). The association of BMD with incident nonspine, fragility fractures to study year 11 was analyzed using Cox proportional hazards analyses, adjusting for age, race, sex, body mass index, hyperparathyroidism, low vitamin D level, and CKD. Interaction terms were used to assess whether the association of BMD with fracture differed in those with and without CKD.

RESULTS

There were 384 incident fractures in 2754 individuals (mean age 73.6 years). Lower FNBMD was associated with greater fracture, regardless of CKD status. After adjustment, the hazard ratios (95% confidence intervals) were 2.74 (1.99, 3.77) and 2.15 (1.80, 2.57) per lower SD FNBMD for those with and without CKD, respectively (interaction P=0.68), and 2.10 (1.23, 3.59) and 1.63 (1.18, 2.23) among those with osteoporosis in patients with and without CKD, respectively (interaction P=0.75).

CONCLUSIONS

BMD provides information on risk for fracture in older individuals with or without moderate CKD.

Fracture risk assessment in patients with chronic kidney disease

Fractures are common in patients with chronic kidney disease (CKD) and associated with substantially high morbidity and mortality. Bone mass measurements are commonly used to assess fracture risk in the general population, but the utility of these measurements in patients with CKD, and specifically among those on hemodialysis, is unclear. This review will outline the epidemiology and etiology of fractures in patients with CKD with a particular emphasis on men and women on hemodialysis. As well, we will summarize the published data, which describes the association between risk factors for fracture (including bone mass measurements, biochemical markers of mineral metabolism, and muscle strength) and fractures in patients with CKD. Patients with CKD suffer from fractures due to impairments in bone quantity, bone quality, and abnormalities of neuromuscular function. There is a paucity of evidence on the associations between bone quality, bone turnover markers, neuromuscular function, and fractures in patients with CKD. Furthermore, the complex etiology of fractures combined with the technical limitations of bone mineral density testing, both by dual energy X-ray absorptiometry (DXA) and by peripheral quantitative tomography (pQCT), limits the clinical utility of bone mass measurements for fracture prediction in CKD; this is particularly true among patients with stages 4 and 5 CKD. Further prospective studies to identify noninvasive measures of bone strength that can be used for fracture risk assessment are needed.

Impact of long-term cinacalcet, ibandronate or teriparatide therapy on bone mineral density of hemodialysis patients: a pilot study

BACKGROUND

Insufficient evidenced-based information is available for the treatment of osteoporosis in hemodialysis (HD) patients.

METHODS

In 102 HD patients, bone mineral density (BMD) was measured twice 16 ± 3 months apart. In the second BMD measurement 66 of them had a femoral neck (FN) T-score <-2.5. Of these 66 patients, 38 consented to a bone biopsy. Depending on both the bone biopsy findings and parathyroid hormone levels, patients were assigned to treatment groups. Eleven patients with osteitis fibrosa and iPTH >300 pg/ml received cinacalcet, 11 with osteitis fibrosa and iPTH <300 pg/ml received ibandronate, 9 with adynamic bone disease received teriparatide, and 7 with mild abnormalities received no treatment. A third BMD measurement was done after an average treatment period of 13-16 months. We compared the annual percent change of FN and lumbar spine (LS) BMD before and during treatment.

RESULTS

FN and LS BMD decreased significantly in the cinacalcet group, with an annual change of 3.6 and 3.4% before treatment to -4.2% (p = 0.04) and -7.7% (p = 0.02) during treatment, respectively. In the teriparatide group, FN and LS BMD increased, although not significantly, with an annual change of -5.4 and -2.6% before treatment to 2.7 and 4.9% during treatment, respectively. In both the ibandronate and the no treatment groups, BMD change rate remained negative during the whole study.

CONCLUSIONS

Teriparatide administration improved BMD in HD patients with adynamic bone disease, although these results did not reach statistical significance. In HD patients with osteitis fibrosa, ibandronate did not improve BMD while cinacalcet reduced BMD.

Bone microarchitecture in hemodialysis patients assessed by HR-pQCT

BACKGROUND AND OBJECTIVES

Dialysis patients are at high risk for low-trauma bone fracture. Bone density measurements using dual-energy x-ray absorptiometry (DXA) do not reliably differentiate between patients with and without fractures. The aim of this study was to identify differences in bone microarchitecture between patients with and without a history of fracture using high-resolution peripheral quantitative computed tomography (HR-pQCT).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Seventy-four prevalent hemodialysis patients were recruited for measurements of areal bone mineral density (aBMD) by DXA and bone microarchitecture by HR-pQCT. Patients with a history of trauma-related fracture were excluded. Forty healthy volunteers served as controls. Blood levels of parathyroid hormone, vitamin D, and markers of bone turnover were determined.

RESULTS

Dialysis patients, particularly women, had markedly impaired bone microarchitecture. Patients with fractures had significantly reduced cortical and trabecular microarchitecture compared with patients without fractures. aBMD tended to be lower in patients with fractures, but differences were statistically not significant. The strongest determinant of fracture was the HR-pQCT-measured trabecular density of the tibia, which also had the highest discriminatory power to differentiate patients according to fracture status. Radial DXA had a lower discriminatory power than trabecular density.

CONCLUSIONS

Bone microarchitecture is severely impaired in dialysis patients and even more so in patients with a history of fracture. HR-pQCT can identify dialysis patients with a history of low-trauma fracture.

Diagnostic usefulness of bone mineral density and biochemical markers of bone turnover in predicting fracture in CKD stage 5D patients--a single-center cohort study

BACKGROUND

In chronic kidney disease stage 5D, diagnostic usefulness of bone mineral density (BMD) in predicting fracture has not been established because of variable results in previous studies. The reason for this may be the heterogeneity of underlying pathogenesis of the fracture.

METHODS

BMD was measured annually and serum biochemistry monthly for 485 hemodialyzed patients from April 2003 to March 2008, and all fractures were recorded.

RESULTS

Forty-six new episodes of any type of fracture and 29 cases of prevalent spine fracture were recorded. Serum bone-specific alkaline phosphatase (b-AP) was a very useful surrogate marker for any type of incident fracture risk [area under curve (AUC) = 0.766, P < 0.0001]. A significantly greater risk of any type of incident fracture was associated with parathyroid hormone (PTH) levels either <150 pg/mL [hazard ratio (HR) = 3.47, P < 0.01] or >300 pg/mL (HR = 5.88, P < 0.0001) compared with 150-300 pg/mL. Receiver-operating characteristic analysis demonstrated a significant predictive power for incident of any type of fracture by BMD at the total hip (AUC = 0.760, P < 0.0001) and other hip regions in females in the lower PTH group (PTH < 204 pg/mL). BMDs at every site but whole body or lumbar spine had significant power to discriminate prevalent spine fracture regardless of gender or PTH.

CONCLUSIONS

Hemodialyzed patients with low or high PTH or increased b-AP had a high fracture risk. BMD by Dual Energy X-ray Absorptiometry (DEXA), especially at the total hip region, was useful to predict any type of incident of fracture for females with low PTH or to discriminate prevalent spine fracture for every patient.

Assessment of bone microarchitecture in chronic kidney disease: a comparison of 2D bone texture analysis and high-resolution peripheral quantitative computed tomography at the radius and tibia

Bone microarchitecture can be studied noninvasively using high-resolution peripheral quantitative computed tomography (HR-pQCT). However, this technique is not widely available, so more simple techniques may be useful. BMA is a new 2D high-resolution digital X-ray device, allowing for bone texture analysis with a fractal parameter (H(mean)). The aims of this study were (1) to evaluate the reproducibility of BMA at two novel sites (radius and tibia) in addition to the conventional site (calcaneus), (2) to compare the results obtained with BMA at all of those sites, and (3) to study the relationship between H(mean) and trabecular microarchitecture measured with an in vivo 3D device (HR-pQCT) at the distal tibia and radius. BMA measurements were performed at three sites (calcaneus, distal tibia, and radius) in 14 healthy volunteers to measure the short-term reproducibility and in a group of 77 patients with chronic kidney disease to compare BMA results to HR-pQCT results. The coefficient of variation of H(mean) was 1.2, 2.1, and 4.7% at the calcaneus, radius, and tibia, respectively. We found significant associations between trabecular volumetric bone mineral density and microarchitectural variables measured by HR-pQCT and H(mean) at the three sites (e.g., Pearson correlation between radial trabecular number and radial H(mean) r = 0.472, P < 0.001). This study demonstrated a significant but moderate relationship between 2D bone texture and 3D trabecular microarchitecture. BMA is a new reproducible technique with few technical constraints. Thus, it may represent an interesting tool for evaluating bone structure, in association with biological parameters and DXA.

Bone mass measurements in men and women with chronic kidney disease

PURPOSE OF REVIEW

Fractures are common in patients with chronic kidney disease (CKD) and are associated with substantial morbidity and mortality. Bone mass measurements are commonly used to assess fracture risk in the general population, but the utility of these measurements in patients with CKD is unclear.

RECENT FINDINGS

This review will outline the epidemiology and etiology of fractures in patients with CKD. Also, we will summarize the published data that describe the association between bone mass measurements and fracture in patients with CKD.

SUMMARY

Patients with CKD suffer from fractures due to impairments in bone quantity, bone quality, and abnormalities of neuromuscular function. The complex etiology of fractures combined with the technical limitations of bone mineral density testing, both by dual energy X-ray absorptiometry and by peripheral quantitative computed tomography, limits the clinical utility of bone mass measurements for fracture prediction in CKD; this is particularly true among patients with stages 4 and 5 CKD. As such, clinicians should not routinely order bone mineral density testing in patients with CKD. Further research, to determine whether bone mineral density together with other noninvasive measures to assess bone strength can predict fracture, is needed.

Bone mass and microarchitecture in CKD patients with fracture

Patients with predialysis chronic kidney disease (CKD) have increased risk for fracture, but the structural mechanisms underlying this increased skeletal fragility are unknown. We measured areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry at the spine, hip, and radius, and we measured volumetric BMD (vBMD), geometry, and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the radius and tibia in patients with CKD: 32 with fracture and 59 without fracture. Patients with fracture had lower aBMD at the spine, total hip, femoral neck, and the ultradistal radius, the last having the strongest association with fracture. By HR-pQCT of the radius, patients with fracture had lower cortical area and thickness, total and trabecular vBMD, and trabecular number and greater trabecular separation and network heterogeneity. At the tibia, patients with fracture had significantly lower cortical area, thickness, and total and cortical density. Total vBMD at both radius and tibia most strongly associated with fracture. By receiver operator characteristic curve analysis, patients with longer duration of CKD had area under the curve of >0.75 for aBMD at both hip sites and the ultradistal radius, vBMD and geometry at the radius and tibia, and microarchitecture at the tibia. In summary, patients with predialysis CKD and fractures have lower aBMD by dual-energy x-ray absorptiometry and lower vBMD, thinner cortices, and trabecular loss by HR-pQCT. These density and structural differences may underlie the increased susceptibility to fracture among patients with CKD.

Bone disease in elderly individuals with CKD

Bone disease can lead to significant morbidity and mortality for those who are afflicted by it, irrespective of etiology. Two very prevalent causes of bone disease that contribute to this are osteoporosis and chronic kidney disease (CKD). The modern era has seen important advances in the understanding and management of these processes, but in elderly patients with CKD it remains a complex issue that has yet to be clearly defined. Changes in mineral metabolism that accompany the loss of renal function result in a spectrum of bone disease that occurs concomitantly with bone loss secondary to aging. As such, the traditional paradigms used to manage bone disease may not be appropriate for these patients. With the aging dialysis population, a better understanding of these 2 processes and their interplay deserves more attention.

Management of osteoporosis in CKD Stages 3 to 5

Osteoporosis and chronic kidney disease (CKD) are both common conditions of older adults and both may be associated with substantial morbidity. However, biochemical and histologic changes that occur with progressive kidney disease require specific interventions, some of which may be concordant with osteoporosis management in the general population, whereas others may be less relevant or perhaps even harmful. In this article, we review the diagnosis of and management strategies for osteoporosis in individuals with CKD, placing these into perspective with the recently published KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for treatment of CKD-mineral and bone disorder (CKD-MBD). Specifically, we highlight osteoporosis treatment recommendations by CKD stage and discuss new avenues for osteoporosis treatment that may be useful in individuals with CKD.

KDOQI US commentary on the 2009 KDIGO Clinical Practice Guideline for the Diagnosis, Evaluation, and Treatment of CKD-Mineral and Bone Disorder (CKD-MBD)

This commentary provides a US perspective on the 2009 KDIGO (Kidney Disease: Improving Global Outcomes) Clinical Practice Guideline for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). KDIGO is an independent international organization with the primary mission of the promotion, coordination, collaboration, and integration of initiatives to develop and implement clinical practice guidelines for the care of patients with kidney disease. The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI), recognizing that international guidelines need to be adapted for each country, convened a group of experts to comment on the application and implementation of the KDIGO guideline for patients with CKD in the United States. This commentary puts the KDIGO guideline into the context of the supporting evidence and the setting of care delivered in the United States and summarizes important differences between prior KDOQI guidelines and the newer KDIGO guideline. It also considers the potential impact of a new bundled payment system for dialysis clinics. The KDIGO guideline addresses the evaluation and treatment of abnormalities of CKD-MBD in adults and children with CKD stages 3-5 on long-term dialysis therapy or with a kidney transplant. Tests considered are those that relate to laboratory, bone, and cardiovascular abnormality detection and monitoring. Treatments considered are interventions to treat hyperphosphatemia, hyperparathyroidism, and bone disease in patients with CKD stages 3-5D and 1-5T. Limitations of the evidence are discussed. The lack of definitive clinical outcome trials explains why most recommendations are not of level 1 but of level 2 strength, which means weak or discretionary recommendations. Suggestions for future research highlight priority areas.

Association of serum alkaline phosphatase and bone mineral density in maintenance hemodialysis patients

Recent studies indicate that serum alkaline phosphatase (AlkPhos), a surrogate of high turnover bone disease, is associated with coronary artery calcification and death risk in maintenance hemodialysis (MHD) patients. The association between AlkPhos and bone mineral density (BMD) is not well studied. We studied the association between AlkPhos and dual-energy X-ray absorptiometry-assessed BMD in a group of MHD patients in Southern California. In 154 MHD patients, aged 55.3 +/- 13.6 years, including 42% women, 38% Hispanics, 42% African Americans, and 55% diabetics, the mean serum AlkPhos was 121 +/- 63 U/L (median: 101, Q(25-75): 81-141); 36% had AlkPhos>/=120 U/L and 50% had a total T-score< or =-1. Whereas the total BMD did not correlate with age (r=0.01, P=0.99) or body mass index (r=0.10, P=0.22), it correlated negatively with AlkPhos (r=-0.25, P=0.002), including after multivariate adjustment (r=-0.24, P=0.003). The proportion of patients with a high coronary artery calcification score>400 was incrementally higher across worsening BMD tertiles (P trend=0.04). The BMD was significantly worse in MHD patients with serum AlkPhos> or =120 U/L compared with <120 U/L (1.01 +/- 0.016 vs. 1.08 +/- 0.013 g/cm(2), respectively, P<0.001). The multivariate adjusted odds ratio of AlkPhos> or =120 U/L for having a total T-score<-1.0 was 2.3 (1.1-4.8, P=0.037). Among routine clinical and biochemical markers, serum AlkPhos> or =120 U/L was a better predictor of total T-score< or =-1 in MHD patients. An association exists between higher serum AlkPhos and worse dual-energy X-ray absorptiometry-assessed BMD in MHD patients. Given these findings, studies are indicated to examine whether interventions that lower serum AlkPhos improve BMD in MHD patients.

Bone mineral density and parathyroid function in patients on maintenance hemodialysis

BACKGROUND

The relationship between parathyroid function, an important determinant of bone turnover, and bone mineral density (BMD) in patients with chronic kidney disease is not fully understood. We wanted to analyze the association between BMD and parathyroid function in hemodialysis patients in details.

METHODS

In a cross-sectional design, data from 270 patients (age 55 ± 15 years, 60% men, all Caucasian) on maintenance hemodialysis were analyzed. All patients underwent dual energy X-ray absorptiometry of the lumbar spine (LS), femoral neck (FN) and distal radius (DR). In addition to routine laboratory tests, blood samples were collected for iPTH, serum markers of bone metabolism (alkaline phosphatase, type I collagen crosslinked-C-telopeptide) and 25OH vitamin D.

RESULTS

Based on Z-scores, bone mineral density was moderately reduced only at the femoral neck in the total cohort. The average Z-score of the "low PTH" group (iPTH < 100 pg/ml) was not different from the Z-score of patients with iPTH in the "target range" (100-300 pg/ml) at any measurement site. While iPTH was negatively correlated with BMD at all measurement sites in patients with iPTH > 100 pg/ml (rho = -0.255, -0.278 and -0.251 for LS, FN and DR, respectively, P < 0.001 for all), BMD was independent of iPTH in patients with iPTH < 100 pg/ml. Furthermore, iPTH was not associated with serum markers of bone metabolism, but these markers were negatively correlated with BMD in the "low PTH" group.

CONCLUSIONS

Low PTH levels are not associated with low BMD in patients with end-stage kidney disease. Furthermore, bone metabolism seems to be independent of iPTH in patients with relative hypoparathyroidism likely reflecting skeletal resistance to PTH.

Arteriovenous fistula affects bone mineral density measurements in end-stage renal failure patients

BACKGROUND AND OBJECTIVES

Hemodialysis needs an arteriovenous fistula (AVF) that may influence the structure and growth of nearby bone and affect bone mass measurement. The study analyzed the effect of AVF in the assessment of forearm bone mineral density (BMD) measured by dual energy x-ray absorptiometry (DXA) and examined its influence on the final diagnosis of osteoporosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Forty patients (52 +/- 18 yr) in hemodialysis program (12 +/- 8 yr) with permeable AVF in forearm were included. Patients were divided in two groups (over and under 50 yr). BMD of both forearms(three areas), lumbar spine, and femur was measured by DXA. Forearm measurements in each arm were compared. Patients were diagnosed as normal only if all territories were considered nonpathologic and osteoporosis/osteopenia was determined by the lowest score found.

RESULTS

Ten patients were excluded and 30 patients were analyzed. BMD in the forearm with AVF was significantly lower than that observed in the contralateral forearm in both groups of patients and in all forearm areas analyzed. When only lumbar spine and femur measurements were considered, 70% of patients were nonpathologic and 30% were osteoporotic. However, inclusion of AVF forearm classified 63% as osteoporotic and a further 27% as osteopenic, leaving only 10% as nonpathologic.

CONCLUSIONS

Forearm AVF affects BMD measurements by decreasing their values in patients with end-stage renal failure. This may produce an overdiagnosis of osteoporosis, which should be taken into account when evaluating patients of this type.

Bone imaging and chronic kidney disease: will high-resolution peripheral tomography improve bone evaluation and therapeutic management?

Bone damage because of chronic kidney disease (CKD) represents a daily challenge for nephrologists. The impact of CKD on bone health may be immediate (serum phosphocalcic disturbances) or delayed (bone fractures and vascular calcifications). Histomorphometry remains the gold standard to evaluate bone, but it is rarely performed in clinical practice. Areal measurement of bone mineral density by dual x-ray absorptiometry is routinely performed to evaluate bone mass. However, this technique presents some limitations. In 2000, the United States National Institutes of Health defined new "quality" criteria for the diagnosis of osteoporosis in addition to decreased bone mass. Bone strength actually integrates two concepts: bone quantity and bone quality (i.e., microarchitectural organization, bone turnover, bone material properties such as mineralization, collagen traits, and microdamage) that cannot be evaluated by dual x-ray absorptiometry. New three-dimensional, noninvasive bone-imaging techniques have thus been developed, e.g., high-resolution peripheral quantitative computed tomography. High-resolution peripheral quantitative computed tomography allows evaluation of both volumetric density and microarchitecture in different compartments of bone, at the distal radius and tibia. High-resolution peripheral quantitative computed tomography may be useful in predicting fractures and assessing bone preventive or therapeutic strategies in CKD patients. It should be evaluated in long-term, longitudinal follow-ups.