Morphometric X-ray absorptiometry in the assessment of vertebral fractures in renal transplant patients

Radiofrequency Echographic Multi Spectrometry (REMS) Technology for Bone Health Status Evaluation in Kidney Transplant Recipients

Background: A significant loss in bone density and strength occurs during the post-renal-transplant period with higher susceptibility to fracture. The study aims to compare the performance of the Radiofrequency Echographic Multi Spectrometry (REMS) in the bone mineral density assessment with the conventional dual-energy X-ray absorptiometry (DXA) in a cohort of kidney transplant recipients (KTR). Methods: A cohort of 40 patients underwent both DXA and REMS examinations on the lumbar spine and/or proximal femur. The paired t-test was used to compare DXA and REMS measurements; the chi-square test was used to compare the prevalence of osteoporosis/osteopenia. The agreement between the two techniques was assessed through Spearman's correlation. Results: As expected, most KTR patients were osteopenic or osteoporotic with both REMS and DXA (86.5% and 81% for the femur; 88% and 65% for the lumbar spine p < 0.05). A modest correlation (r = 0.4, p < 0.01) was observed at the lumbar spine between the T-score measured by REMS and DXA. A strong correlation was defined between REMS and DXA in the femoral region (r = 0.7, p < 0.0001). Conclusions: The study demonstrates the exchangeability of the two techniques on the proximal femur in KTR and a higher diagnostic accuracy of REMS at the spine level than DXA.

Clinical predictors of incipient vertebral fractures and bone mineral density in kidney transplant patients

PURPOSE

Kidney transplant recipients are prone to metabolic bone diseases and consequent fractures. This study aimed to evaluate the incidence of incipient vertebral fractures, osteopenia, osteoporosis, and the clinical factors associated with incipient vertebral fractures in a group of kidney transplant patients.

METHODS

Two hundred sixty-four patients (F/M 124/140, 45.3 ± 13 years) who had undergone kidney transplantation in tertiary care centers were included. Vertebral fractures were assessed semiquantitatively using conventional thoracolumbar lateral radiography in 202 of the patients.

RESULTS

Vertebral fractures were observed in 56.4% (n = 114) of the study group. The frequency of osteoporosis was 20.0% (53 of 264 patients), and osteopenia was 35.6% (94 of 264 patients). Bone mineral density (BMD) levels were in the normal range in 40.3% (n = 46) of the subjects with vertebral fractures. It was in the osteoporotic range in 20.1% (n = 23) and the osteopenic range in 40.3% (n = 46). Vertebral fractures were associated with age, duration of hemodialysis, BMI, and femoral neck Z score (R² 37.8%, p = 0.027).

CONCLUSION

As incipient vertebral fractures can be observed in patients with normal BMD levels in kidney transplant recipients, conventional X-ray screening for vertebral fractures may be beneficial for a proper therapy decision of metabolic bone disease in kidney transplant recipients.

Low bone density, vertebral fracture and FRAX score in kidney transplant recipients: A cross-sectional cohort study

Background

Kidney transplantation (KT) recipients are at increased risk of low bone density (LBD) and fractures. In this retrospective study, we investigated bone mineral density (BMD), vertebral fractures, calculated risk for major osteoporotic fractures (MOF), and hip fractures in the KT recipients.

Patients-method

Patients who completed at least one year after KT were included in the analysis. Demographic, clinical, and laboratory data were recorded. Measurements of BMD were performed by dual-energy X-ray absorptiometry. Vertebral fractures were assessed using semi-quantitative criteria with conventional radiography. The ten-year risk for MOF and hip fracture were calculated using the FRAX@ tool with BMD.

Results

One hundred fifty-three KT recipients were included in the study. The population included 77 women. The mean age at evaluation was 46,5±11,9 years. Seventy-eight (50.9%) patients had normal femoral neck BMD while osteoporosis and osteopenia at the femoral neck were present in 12 (7.8%) and 63 (41.1%) of the patients, respectively. Age at evaluation was the risk factor for LBD (OR 1.057; 95% CI 1.024–1.091; p = 0.001). In female KT recipients, LBD was principally affected by menopausal status whereas in males, mammalian target of rapamycin (mTOR) inhibitor use and lower BMI levels were the risk factors. The prevalent vertebral fracture was found in 43.4% of patients. In multivariate analysis, only steroid use (OR 0.121; 95% CI 0.015–0.988; p = 0.049) was found to be associated with prevalent fracture. Among all KT recipients, 1.9% had a high MOF probability (≥20% risk of fracture), and 23.5% had high hip fracture probability (≥3% risk of hip fracture) according to FRAX.

Conclusion

Exploring the prevalence of LBD and vertebral fracture and the risk factors would help clinicians to modify long-term follow-up strategies. Furthermore, the high hip fracture risk probability in our cohort suggested that there is a need for longitudinal studies to confirm the validity of the FRAX tool in the transplant population.

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.

Focus on the Possible Role of Dietary Sodium, Potassium, Phosphate, Magnesium, and Calcium on CKD Progression

The impressive estimated number of chronic kidney disease (CKD) patients in the world justifies any possible effort at implementing preventive measures of disease progression. Renal insufficiency is associated with significant changes in the electrolyte handling and body balance of sodium, potassium, phosphate, magnesium, and calcium, all of which are biologically vital molecules. Dietary habits could contribute significantly to the optimal management of possible derangements. In this review, we examined the available evidence recommending dietary prescriptions for these five elements aiming at reducing CKD progression. Clear evidence that specific dietary prescriptions may halt or reduce CKD progression is lacking. However, some practical recommendations are possible to prescribe the best possible therapy to the individual CKD patient.

Cardiovascular calcifications in kidney transplant recipients

Vascular and valvular calcifications are highly prevalent in kidney transplant recipients and are associated with an increased risk of cardiovascular events, which represent the leading cause of long-term mortality in these patients. However, cardiovascular calcification has been traditionally considered as a condition mostly associated with advanced chronic kidney disease stages and dialysis, and comparatively fewer studies have assessed its impact after kidney transplantation. Despite partial or complete resolution of uremia-associated metabolic derangements, kidney transplant recipients are still exposed to several pro-calcifying stimuli that favour the progression of pre-existing vascular calcifications or their de novo development. Traditional risk factors, bone mineral disorders, inflammation, immunosuppressive drugs and deficiency of calcification inhibitors may all play a role, and strategies to correct or minimize their effects are urgently needed. The aim of this work is to provide an overview of established and putative mediators involved in the pathogenesis of cardiovascular calcification in kidney transplantation, and to describe the clinical and radiological features of these forms. We also discuss current evidence on preventive strategies to delay the progression of cardiovascular calcifications in kidney transplant recipients, as well as novel therapeutic candidates to potentially prevent their long-term deleterious effects.

Bone Mineral Density and Aortic Calcification: Evidence for a Bone-vascular Axis After Kidney Transplantation

BACKGROUND

Chronic kidney disease mineral and bone disorders (CKD-MBD) and vascular calcification are often seen in kidney transplantation recipients (KTR). This study focused on the bone-vascular axis hypothesis, the pathophysiological mechanisms driving both bone loss and vascular calcification, supported by an association between lower bone mineral density (BMD) and higher risk of vascular calcification.

METHODS

KTR referred for a dual-energy X-ray absorptiometry procedure within 6 mo after transplantation were included in a cross-sectional study (2004-2014). Areal BMD was measured at the proximal femur, and abdominal aortic calcification (AAC) was quantified (8-points score) from lateral single-energy images of the lumbar spine. Patients were divided into 3 AAC categories (negative-AAC: AAC 0; low-AAC: AAC 1-3; and high-AAC: AAC 4-8). Multivariable-adjusted multinomial logistic regression models were performed to study the association between BMD and AAC.

RESULTS

We included 678 KTR (51 ± 13 y old, 58% males), 366 (54%) had BMD disorders, and 266 (39%) had detectable calcification. High-AAC was observed in 9%, 11%, and 25% of KTR with normal BMD, osteopenia, and osteoporosis, respectively (P < 0.001). Higher BMD (T-score, continuous) was associated with a lower risk of high-AAC (odds ratio 0.61, 95% confidence interval 0.42-0.88; P = 0.008), independent of age, sex, body mass index, estimated glomerular filtration rate, and immunosuppressive therapy. KTR with normal BMD were less likely to have high-AAC (odds ratio 0.24, 95% confidence interval 0.08-0.72; P = 0.01).

CONCLUSIONS

BMD disorders are highly prevalent in KTR. The independent inverse association between BMD and AAC may provide evidence to point toward the existence, while highlighting the clinical and epidemiological relevance, of a bone-vascular axis after kidney transplantation.

Bone, inflammation and chronic kidney disease

Increasing knowledge on inflammatory mediators and bone metabolism highlights the relationship between inflammation and bone disease. During acute illness, inflammatory cells and cytokines modulate bone cells activity so as to mobilize calcium seemingly to supply the metabolic requirements for immune response. In case of long lasting, chronic inflammatory states a condition of maladaptive, smouldering inflammation is realized and negatively affects calcium bone balance. Aging, now nicknamed inflammaging, is regarded as a chronic inflammatory condition, characterized by increased circulating inflammatory cytokines, that contributes to the development of osteoporosis, cardiovascular diseases and chronic kidney disease. In patients with renal insufficiency, the development of bone and mineral disorders (so called CKD-MBD "syndrome") is now a recognized pathogenic factor for the seemingly accelerated process of aging and for the increased risk of cardiovascular death in these patients. The adaptive changes in mineral and bone metabolism developing in the early stages of chronic kidney disease could represent a hypothetical model of accelerated aging, osteoporosis and cardiovascular disease.

Osteoporosis, bone mineral density and CKD-MBD complex (I): Diagnostic considerations

Osteoporosis (OP) and chronic kidney disease (CKD) independently influence bone and cardiovascular health. A considerable number of patients with CKD, especially those with stages 3a to 5D, have a significantly reduced bone mineral density leading to a high risk of fracture and a significant increase in associated morbidity and mortality. Independently of classic OP related to age and/or gender, the mechanical properties of bone are also affected by inherent risk factors for CKD ("uraemic OP"). In the first part of this review, we will analyse the general concepts regarding bone mineral density, OP and fractures, which have been largely undervalued until now by nephrologists due to the lack of evidence and diagnostic difficulties in the context of CKD. It has now been proven that a reduced bone mineral density is highly predictive of fracture risk in CKD patients, although it does not allow a distinction to be made between the causes which generate it (hyperparathyroidism, adynamic bone disease and/or senile osteoporosis, etc.). Therefore, in the second part, we will analyse the therapeutic indications in different CKD stages. In any case, the individual assessment of factors which represent a higher or lower risk of fracture, the quantification of this risk (i.e. using tools such as FRAX^®) and the potential indications for densitometry in patients with CKD could represent an important first step pending new clinical guidelines based on randomised studies which do not exclude CKD patients, all the while avoiding therapeutic nihilism in an area of growing importance.

Value and potential limitations of vertebral fracture assessment (VFA) compared to conventional spine radiography: experience from a fracture liaison service (FLS) and a meta-analysis

We evaluated the value of VFA in the identification of vertebral fractures using a retrospective study and a meta-analysis. Performance of VFA was adequate in the meta-analysis although this was not demonstrated in our centre. We recommend checking the performance of VFA tools before exclusively relying on this tool.

INTRODUCTION

Vertebral fractures are traditionally diagnosed using conventional radiographs of the spine. Vertebral fracture assessment (VFA) has been advocated as an alternative tool in the diagnosis of these fractures.

METHODS

We conducted a retrospective study as well as a systematic review and a meta-analysis to evaluate the performance of VFA compared to conventional spinal radiography in patients who had sustained a fracture and thus at risk for osteoporosis. A risk of bias analysis was also performed.

RESULTS

The diagnostic study included 542 patients (25% male) with fractures. The sensitivity of low-radiation VFA to detect a patient with a vertebral fracture ≥ Genant grade 2 was 0.77 and its specificity 0.80. Two hundred ninety-seven (55%) patients had ≥1 and 135(25%) ≥3 unevaluable vertebrae. The systematic review identified 16 studies including a total of 3238 subjects (19% male) with a mean age range of 45 to 74 years. Seven studies had a low risk of bias and 9 had an intermediate risk, mainly due to not consecutively including patients. The pooled sensitivity of VFA to detect a patient with a vertebral fracture ≥Genant grade 2 was 0.84 (95% CI, 0.72-0.92) and specificity 0.90 (95% CI, 0.84-0.94).

CONCLUSIONS

Our findings from the meta-analysis suggest an adequate performance of VFA for the detection of vertebral fractures. However, we could not demonstrate these findings in our center, especially the specificity. Our data advocate caution with exclusively relying on VFA in the assessment of vertebral fractures without identifying performance and potential limitations of the technique.

Serum phosphorus levels and fracture following renal transplantation

PURPOSE

Increased fracture rates are observed in renal transplant recipients (RTRs) compared with the general population. Risk factors include age, diabetes, dialysis vintage, immunosuppression and mineral and bone disorders.¹ Low serum phosphorus levels occur post-transplantation; however, its relationship with fracture risk has not been evaluated. The purpose of this study was to evaluate risk factors for fracture in RTRs at a single tertiary referral centre.

METHODS

A retrospective cross-sectional analysis of 146 patients (75 M, 71 F) who had been referred for dual energy X-ray densitometry (DXA) post-renal transplantation was performed. Aetiology of end stage kidney disease (ESKD), duration of dialysis, parathyroidectomy history, immunosuppression regimen, bone mineral density (BMD), biochemistry and fractures were documented. Statistical analyses included univariable and multivariable regression.

RESULTS

The mean age of patients was 54 years and mean time post-transplantation 6.7 years. A total of 79 fractures occurred in 52 patients (35%), with 40 fractures occurring post-transplantation. Ankle/foot fractures were most common (48%). Lower serum phosphorus levels and declining femoral neck (FN) T-score and were associated with fractures in both univariable and multivariable regression analyses after adjusting for age, gender, weight, estimated glomerular filtration rate and pre-transplant history of fracture (P=.011 and P=.042 respectively). The relationship between serum phosphorus and fracture remained significant independent of FN T-score, parathyroid hormone levels, parathyroidectomy status and prednisolone use.

CONCLUSION

Fracture was common post-renal transplantation. Lower serum phosphorus levels and declining FN T-scores were associated with fractures. The mechanism of this previously unreported observation requires further evaluation in prospective studies.

Bone fractures and lumbar mineral density after renal transplantation. A long-term cross-sectional study

BACKGROUND

The purpose of this work was to investigate the association of vertebral and peripheral fractures 10 yr after grafting with bone metabolic markers and body mass density (BMD).

PATIENTS AND METHODS

One hundred thirty-eight recipients with stable graft function were included in a cross-sectional study. Graft function, biochemical mineral metabolism markers and body mass density (DEXA) were measured. Vertebral fractures were assessed by a semiquantitative analysis of lateral spine X-ray exam.

RESULTS

At the time of the study, intact parathyroid hormone levels were 127.5 ± 78.4 pg/mL and serum calcidiol 20.4 ± 9.3 ng/mL. DEXA showed osteopenia in 47% and osteoporosis in 23% at lumbar spine, 51% and 14% at femoral neck, and 53% and 8% at trochanter. Eighty-five recipients presented vertebral fractures, 69 mild and 16 moderate/severe fractures. In the multivariate analysis, vertebral fractures were associated with older age (p = 0.010), length of follow-up (p = 0.022) and trochanter T-score (p = 0.038). Twenty-three patients presented peripheral fractures and 19 of them also had vertebral fractures. Patients with peripheral fractures were younger, mostly women and had lower BMD.

CONCLUSIONS

Vertebral fractures were associated with lower BMD at trochanter. Most fractures were mild and were several times more frequent than in general population. Their clinical significance needs to be determined.

A systematic review of diagnostic accuracy of vertebral fracture assessment (VFA) in postmenopausal women and elderly men

This systematic review was performed to compare the diagnostic accuracy of vertebral fracture assessment (VFA) with that of spinal radiography for identification of vertebral fractures (VFs). VFA appeared to have moderate sensitivity and high specificity for detecting VFs when compared with spinal radiography.

INTRODUCTION

VFs are recognized as the hallmark of osteoporosis, and a previous VF increases the risk of a future fracture. Therefore, the timely detection of VFs is important for prevention of further fractures. This systematic review examined the diagnostic accuracy of VFA using dual X-ray absorptiometry (DXA) to identify VFs.

METHODS

We searched for potentially relevant studies using electronic databases, including Ovid-Medline, Ovid-EMBASE, Cochrane library, and four Korean databases, from their inception to May 2013. We compared the diagnostic accuracy of VFA with that of spinal radiography for detection of VFs by analyzing the sensitivity and specificity using a 2 × 2 contingency table. Subgroup analyses were also performed on studies with a low risk of bias and applicability.

RESULTS

Twelve studies were analyzed for the diagnostic accuracy of VFA. The sensitivity and specificity were 0.70-0.93 and 0.95-1.00, respectively, analyzed on a per-vertebra basis, and 0.65-1.00 and 0.74-1.00 on a per-patient basis. The sensitivity and specificity of five studies in subgroups with a low risk of bias in the intervention test were 0.70-0.84 and 0.96-0.99, respectively. In studies with a low risk of bias in the patient selection, those based on a per-vertebra basis in three studies were 0.70-0.93 and 0.96-1.00, respectively.

CONCLUSIONS

VFA had moderate sensitivity and high specificity for detecting VF when compared with spinal radiography. However, the present findings are insufficient to assess whether spinal radiography should be replaced by VFA.

Mineral metabolism disorders, vertebral fractures and aortic calcifications in stable kidney transplant recipients: The role of gender (EMITRAL study)

BACKGROUND AND OBJECTIVES

The relationship between mineral metabolism disorders, bone fractures and vascular calcifications in kidney transplant recipients has not been established.

METHOD

We performed a cross-sectional study in 727 stable recipients from 28 Spanish transplant clinics. Mineral metabolism parameters, the semi-quantification of vertebral fractures and abdominal aortic calcifications were determined centrally.

RESULTS

Vitamin D deficiency (25OHD3<15ng/ml) was more common in female recipients at CKD-T stages I-III (29.6% vs 44.4%; p=0.003). The inverse and significant correlation between 25OHD3 and PTH was gender-specific and women exhibited a steeper slope than men (p=0.01). Vertebral fractures (VFx) with deformity grade ≥2 were observed in 15% of recipients. Factors related to VFx differed by gender; in males, age (OR 1.04; 95% CI 1.01-1.06) and CsA treatment (OR: 3.2; 95% CI: 1.6-6.3); in females, age (OR 1.07; 95% CI: 1.03-1.12) and PTH levels (OR per 100pg/ml increase: 1.27; 95% CI: 1.043-1.542). Abdominal aortic calcifications were common (67.2%) and related to classical risk factors but not to mineral metabolism parameters.

CONCLUSIONS

Vitamin D deficiency is more common among female kidney transplant recipients at earlier CKD-T stages, and it contributes to secondary hyperparathyroidism. Prevalent vertebral fractures are only related to high serum PTH levels in female recipients.

Is Klotho F352V Polymorphism the Missing Piece of the Bone Loss Puzzle in Renal Transplant Recipients?

BACKGROUND

Bone disorders are next to cardiovascular problems in frequency in renal transplant (RT) recipients. Reduction in 1,25-dihydroxycholecalciferol (1,25D) levels is among the reasons causing bone loss in these patients. Klotho (KL) serves as a co-receptor for fibroblast growth factor 23 (FGF23), and functions in vitamin D metabolism. KL polymorphisms have been identified in several studies, and phenylalanine to valine substitution at amino acid position 352 seemed to be important to KL function. We investigated KL F352V polymorphism and its relation with 1,25D levels in RT recipients.

METHODS

The study included 25 RT recipients (8 female, 17 male) and 26 (14 female, 12 male) healthy control subjects who were wild (FF) phenotypes in terms of KL F352V polymorphism. RT recipients with (FV, n = 11) and without (FF, n = 14) a heterozygote polymorphism were determined with high resolution DNA melting analysis of KL F352V polymorphism. Serum 1,25D levels were measured using the RIA method.

RESULTS

RT recipients with FV phenotype had significantly lower 1,25D levels (17.58 ± 18.38 pg/ml) compared to recipients with FF phenotype (44.91 ± 24.68 pg/ml) and control subjects (28.24 ± 12.13 pg/ml). 1,25D levels in RT recipients with FF phenotype were significantly higher than control subjects.

CONCLUSIONS

KL F352V polymorphism may increase the expression of FGF23 co-receptor, KL protein and thus may decrease renal expression of 1α-hydroxylase, and/or stimulate 24-hydroxylase in RT recipients. The resultant decrease 1,25D levels may participate in bone loss in these patients.

Vertebral morphometry by dual-energy X-ray absorptiometry (DXA) for osteoporotic vertebral fractures assessment (VFA)

PURPOSE

This study was done to evaluate the diagnostic accuracy of dual-energy X-ray absorptiometry (DXA) compared with conventional radiography for identifying vertebral fractures.

MATERIALS AND METHODS

A total of 930 postmenopausal women underwent conventional radiography and DXA imaging of the spine. The images were evaluated by two expert skeletal radiologists using the semiquantitative (SQ) method for conventional radiography and the morphometric vertebral fracture assessment (VFA) for DXA.

RESULTS

The SQ method for radiography (SQ-Rx) analysed 99.1% of vertebrae, identifying 442 vertebral fractures; VFA analysed 97.5% vertebrae, detecting 420 vertebral fractures. Agreement between SQ-Rx and VFA reached 98.76%, and the κ-score was 0.96 [95% confidence interval (CI), 0.95-0.98]. Assessing the grading of vertebral fractures, agreement reached 97.5% and the κ-score was 0.841 (95% CI, 0.821-0.891). Considering SQ-Rx method as "gold standard", VFA had a sensitivity of 97.85 % and a specificity of 99.81%. The negative (NPV) and positive (PPV) predictive value for VFA were 99.83 % and 98.15%, respectively. Fractures were identified in 251 (27 %) and 242 (26 %) of patients on SQ-Rx and VFA, respectively. On a per-patient basis, the agreement between the two methods was 97% and the κ-score was 0.95 (95% CI, 0.920-0.968). The diagnostic parameters for VFA were 97.23% sensitivity, 98.86% specificity, 97.60% PPV and 98.84% NPV.

CONCLUSIONS

This study demonstrated that VFA with DXA may reach a high level of accuracy for diagnosing vertebral fractures, suggesting that VFA should be introduced in the screening of individuals with a risk of osteoporosis and in the follow-up of osteoporotic patients receiving treatment.

Vertebral morphometry by X-ray absorptiometry: which reference data for vertebral heights?

INTRODUCTION

The recent improvement in the resolution of dual-energy X-ray absorptiometry (DXA) images enables most vertebral levels to be seen adequately and thus DXA may be a worthwhile alternative to radiologic morphometry for the identification of vertebral fractures (VF). In this multicenter study, we have derived reference data for vertebral heights and their ratios in Italian women using morphometric X-ray absorptiometry (MXA).

METHODS

DXA scans were acquired in 1254 consecutive pre- and postmenopausal women, (mean age 63.7 ± 11.3, range 26-88 yrs), referred to six osteoporosis centers. MXA analysis of these images was performed by the same operator measuring vertebral heights and height ratios from L4 to T4. We calculated measures of central tendency and dispersion of vertebral heights and vertebral ratios using different approaches (mean and standard deviation as well as median and interquartile range of raw data, mean and standard deviation of trimmed data using an iterative algorithm, and mean and standard deviation of not fractured vertebrae).

RESULTS

Independently of the approach that we used, all the measures of central tendency were similar, while significant differences were found when compared with reference ranges in other populations. The vertebral heights of our sample at every vertebral level were significantly smaller than both Rea population and the Lunar reference values, even after normalization. Splitting data according to age groups, there was a decrease in the vertebral heights and ratios between the younger and older women.

CONCLUSIONS

This study demonstrates that reference data for MXA should be population specific and age matched.

Vertebral morphometry

Visual semiquantitative (SQ) assessment of the radiographs by a trained and experienced observer is the "gold standard" method to detect vertebral fractures. Vertebral morphometry is a quantitative method to identify osteoporotic vertebral fractures based on the measurement of vertebral heights. Vertebral morphometry may be performed on conventional spinal radiographs (MRX: morphometric x-ray radiography) or on images obtained from dual x-ray absorptiometry (DXA) scans (MXA: morphometric x-ray absorptiometry). Vertebral fracture assessment (VFA) indicates the method for identification of the vertebral fractures using lateral spine views acquired by DXA, with low-dose exposition. For epidemiologic studies and clinical drug trials in osteoporosis research but also in clinical practice, the preferred method is radiographic SQ assessment., because an expert eye can better distinguish between true fractures and vertebral anomalies than can quantitative morphometry. However, vertebral morphometry, calculating the deformity of overall thoracic and lumbar spine, may supply useful data about the vertebral fracture risk. VFA performed during routine densitometry allows identification, by visual or morphometric methods, of most osteoporotic vertebral fractures, even those that are asymptomatic.

Prevalence of Osteoporosis, Osteopenia, and Vertebral Fractures in Long-Term Renal Transplant Recipients

BACKGROUND

Osteopenia and osteoporosis are frequent complications early after transplantation. Their long-term prevalences and associations with the risk of fractures are not well known. The objective of the present work was to determine the incidence of osteopenia and osteoporosis versus vertebral fractures in renal transplant recipients with stable graft function and with a follow-up of at least 10 years.

PATIENTS AND METHODS

Forty renal transplant recipients, 24 men and 16 women, were included in the study. The mean age was 41.8 years and the follow-up was 130 +/- 14 months. Initial immunosuppression consisted of cyclosporine with or without an antiproliferative agent. Measurements of bone mass density (BMD) were performed by dual-energy X-ray absorptiometry (DEXA). The assessment of vertebral fracture using conventional radiography was evaluated by semiquantitative criteria.

RESULTS

Eleven patients (27.5%) displayed lumbar spine osteoporosis (T-score < -2.5); 21 (52.5%), osteopenia (T-score > -2.5 and < -1) and 8 (20.0%), normal BMD. However, BMD was better preserved at the femoral neck: 14 patients (35.0%) had normal BMD; 20 (50.0%) osteopenia, and 6 (15.0%), osteoporosis. When analyzed together, patients with osteoporosis or osteopenia showed worse graft function at 1 and 8 years compared with normal BMD patients (1.75 +/- 0.634 vs 1.32 +/- 0.33 mg/dL at 1 year; P < .014) and (1.7 +/- 0.4 vs 1.2 +/- 0.2 mg/dL at 5 years; P < .01) and a greater number were prescribed vitamin D (50% vs 23%). Mild vertebral fractures were observed in 60.0% patients with osteoporosis; 70% with osteopenia; and 43% with normal lumbar BMD. Peripheral fractures were more common in patients with osteoporosis (P = .053).

CONCLUSIONS

Osteoporosis and osteopenia are common among long-term renal transplant recipients are associated with poorer graft function. Lumbar spine BMD osteoporosis is associated with peripheral fractures. However, mild vertebral deformities are not associated with the presence of osteopenia or osteoporosis.