FRAX prognostic and intervention thresholds in the management of major bone fractures in hemodialysis patients: A two-year prospective multicenter cohort study

Vertebral fractures in patients with CKD and the general population: a call for diagnosis and action

Vertebral fractures (VFs) are the most common osteoporotic fractures in the general population, and they have been associated with high mortality, decreased quality of life, and high risk of subsequent fractures, especially when recent, multiple, or severe. Currently, VF diagnosis and classification determine fracture risk and the most appropriate anti-osteoporotic treatment. However, VFs are clearly underdiagnosed, especially in patients with chronic kidney disease (CKD), and CKD-associated osteoporosis has been disregarded until recently. VFs are associated with higher morbidity and mortality, and their prevalence and incidence differ depending on the grade of renal dysfunction (CKD G1-G5) and/or the type of renal replacement therapy (dialysis or transplantation). In addition to classical risk factors [such as higher age, female sex, reduced bone mineral density, diabetes and steroid use], various other factors have been associated with an increased risk of VFs in CKD, including CKD grade, haemodialysis vintage, time since renal transplantation, low or high intact parathyroid hormone and phosphate levels, and/or vitamin D and K1 deficiencies. Importantly, several clinical societies have recently modified their algorithms according to the fracture risk classification (including the presence of VFs) and determined the most appropriate anti-osteoporotic treatment for the general population. However, there are no specific guidelines addressing this topic in patients with CKD despite an important paradigm shift regarding the prognostic value of bone mineral density in 2017 after the publication of the CKD-Mineral and Bone Disorder Kidney Disease: Improving Global Outcomes guidelines. A proactive attitude towards diagnosis, treatment, and research is proposed to avoid therapeutic nihilism.

Ten tips on how to assess bone health in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) experience a several-fold increased risk of fracture. Despite the high incidence and the associated excess morbidity and premature mortality, bone fragility in CKD, or CKD-associated osteoporosis, remains a blind spot in nephrology with an immense treatment gap. Defining the bone phenotype is a prerequisite for the appropriate therapy of CKD-associated osteoporosis at the patient level. In the present review, we suggest 10 practical 'tips and tricks' for the assessment of bone health in patients with CKD. We describe the clinical, biochemical, and radiological evaluation of bone health, alongside the benefits and limitations of the available diagnostics. A bone biopsy, the gold standard for diagnosing renal bone disease, is invasive and not widely available; although useful in complex cases, we do not consider it an essential component of bone assessment in patients with CKD-associated osteoporosis. Furthermore, we advocate for the deployment of multidisciplinary expert teams at local, national, and potentially international level. Finally, we address the knowledge gaps in the diagnosis, particularly early detection, appropriate "real-time" monitoring of bone health in this highly vulnerable population, and emerging diagnostic tools, currently primarily used in research, that may be on the horizon of clinical practice.

Bone health as a co-morbidity of chronic kidney disease

Chronic kidney disease and osteoporosis commonly co-exist in aged patients. Chronic kidney disease affects bone health because of its effect on mineral metabolism in the syndrome, Chronic Kidney Disease Mineral and Bone Disorder, resulting in an increased risk of fractures. Hip fracture risk may be as much as four-fold higher in the worst affected. Tools to estimate fracture risk such as FRAX® and measuring bone density can be used in patients with chronic kidney disease; however, bone density may underestimate fracture risk in this population as it does not give information on bone quality. While osteoporosis treatment in patients with chronic kidney disease stage 1-3 does not differ from the general population, in the absence of Chronic Kidney Disease Mineral and Bone Disorder, patients with disease stage 4-5 require special consideration. It is, however, of the utmost importance that these patients receive pharmacological treatment because of their high risk of fractures.

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.

Trabecular bone score and phalangeal quantitative ultrasound are associated with muscle strength and fracture risk in hemodialysis patients

There is growing interest in the relationship between chronic kidney disease (CKD) and fragility fracture risk. Bone mineral density (BMD) is a major determinant of bone strength, although its role as a predictor of fracture in advanced CKD and hemodialysis is still under debate. We aimed to further investigate surrogates of bone quality and their associations with muscle strength and fracture risk in hemodialysis. Multiple clinical risk factors for fracture and an estimated 10-year probability of fracture, BMD at lumbar spine and femur, trabecular bone score (TBS), X-ray vertebral morphometry, phalangeal bone quantitative ultrasonography (QUS), tibial pulse-echo ultrasonography (PEUS), and handgrip strength were evaluated in a setting of hemodialysis patients in treatment with acetate-free biofiltration (AFB) or bicarbonate hemodialysis. The bone ultrasound measurements, both at phalangeal and tibial sites, were significantly associated with lumbar and femoral DXA values. Handgrip strength was significantly associated with the 10-year probability of fracture (r = -0.57, p < 0.001 for major fractures and r = -0.53, p < 0.001 for hip fracture, respectively), with femur neck, total femur, and L1-L4 BMD values (r = 0.47, p = 0.04; r = 0.48, p = 0.02; r = 0.58, p = 0.007, respectively), with TBS at the lumbar spine (r = 0.71, p < 0.001) and with the phalangeal QUS measure of AD-SoS (r = 0.369, p = 0.023). In the hemodialysis group, 10 participants (24.3%) reported at least one morphometric vertebral fracture (Vfx); conversely, only six participants (15%) showed Vfx in the control group. In the hemodialysis group, participants with Vfx compared with participants without Vfx reported significantly different TBS, bone transmission time (BTT), cortical thickness, and handgrip strength (p < 0.05). At multiple regression analysis, by identifying as dependent variable the 10-year fracture risk for major fracture, after correcting for age, BMI, time since dialysis, AD-SoS, cortical bone thickness, and handgrip strength, only BTT (β = -15.21, SE = 5.91, p = 0.02) and TBS (β = -54.69, SE = 21.88, p = 0.02) turned out as independently associated with fracture risk. In conclusion, hemodialysis patients showed a higher fracture risk and lower surrogate indices of bone strength as TBS and QUS parameters. In this cohort of patients, handgrip strength measurements appeared to be a useful instrument to identify high-fracture-risk subjects.

Bone Fragility Fractures in CKD Patients

Chronic kidney diseases (CKD) are associated with mineral and bone diseases (MBD), including pain, bone loss, and fractures. Bone fragility related to CKD includes the risk factors observed in osteoporosis in addition to those related to CKD, resulting in a higher risk of mortality related to fractures. Unawareness of such complications led to a poor management of fractures and a lack of preventive approaches. The current guidelines of the Kidney Disease Improving Global Outcomes (KDIGO) recommend the assessment of bone mineral density if results will impact treatment decision. In addition to bone density, circulating biomarkers of mineral, serum bone turnover markers, and imaging techniques are currently available to evaluate the fracture risk. The purpose of this review is to provide an overview of the epidemiology and pathogenesis of CKD-associated bone loss. The contribution of the current tools and other techniques in development are discussed. We here propose a current view of how to better predict bone fragility and the therapeutic options in CKD.