Comparison of T-scores from different skeletal sites in differentiating postmenopausal women with and without prevalent vertebral fractures

Asymptomatic vertebral fracture in Tunisian post-menopausal women at risk: prevalence and risk factors

Data are still scarce regarding the prevalence and the associated factors of vertebral fractures (VF) in the North Africa and the Middle East region. In this study, VF were common in at risk Tunisian women with a prevalence of 26.19%. Lower total hip T-score, having severe back pain, and being physically inactive were independently associated with VF.

INTRODUCTION

Vertebral fractures are related to a marked increase in morbidity and mortality and they are associated with a definite risk of subsequent fracture. Nevertheless, they remain underdiagnosed and little is known about their epidemiology in the African countries. In this first Tunisian study, we aimed to assess the prevalence and the associated factors of asymptomatic VF among at risk Tunisian post-menopausal women.

METHODS

In this cross-sectional study, we included post-menopausal women without a previous diagnosis of VF and who were referred for bone mineral density (BMD) measurement. Each participant had had an extensive medical history investigation, a BMD assessment, and a vertebral fracture assessment (VFA) scan using a dual energy X-ray absorptiometry. VF were defined using Genant semi-quantitative method.

RESULTS

Two hundred and ten post-menopausal women were included. The overall prevalence of VF was 26.19% and 9.52% of our participants had multiple VF. The prevalence of VF was significantly higher in older participants, those having a history of prior severe fragility fracture, or having at least one intrinsic fall. The percentage of low bone mineral density and osteoporosis were significantly higher in women with VF. After binary logistic regression analysis, severe back pain (OR = 3.016; 95% CI 1.304-6.974), regular physical activity (OR = 0.065; 95% CI 0.02-0.213), and total hip T-score (OR = 0.56; 95% CI 0.383-0.820) were independently associated with VF.

CONCLUSION

VF are very prevalent among at risk Tunisian post-menopausal women and their incorporation in a clinical and densitometric tool might identify more effectively subsequent fracture.

Contribution of Lumbar Spine BMD to Fracture Risk in Individuals With T-Score Discordance

Fracture risk estimates are usually based on femoral neck (FN) BMD. It is unclear how to address T-score discordance, where lumbar spine (LS) T-score is lower than FN T-score. The objective of this work was to examine the impact of LS BMD on fracture risk, in individuals with lower LS T-score than FN T-score. Participants aged 60+ years from the Dubbo Osteoporosis Epidemiology Study with LS and FN BMD measured at first visit, and were followed from 1989 to 2014. Five-hundred and seventy-three (573) of 2270 women and 131 of 1373 men had lower LS than FN T-score by ≥ 0.6 standard deviation (SD) (low-LS group based on least significant change). In low-LS women, each 1 SD lower LS T-score than FN was associated with a 30% increase in fracture risk (hazard ratio [HR] 1.30; 95% CI, 1.11 to 1.45). For low-LS men there was a 20% nonsignificant increase in fracture risk for each 1 SD lower LS than FN T-score (HR 1.20; 95% CI, 0.10 to 1.67). Low-LS women had greater absolute fracture risks than the rest of the women. This increased risk was more apparent for lower levels of FN T-score and in older age groups. At an FN T-score of -2, low-LS women had a 3%, 10%, and 23% higher 5-year absolute fracture risk than non-low LS women in the 60 to 69 year, 70 to 79 year, and 80+ years age-groups, respectively. Furthermore, an osteoporotic LS T-score increased 5-year absolute fracture risk for women with normal or osteopenic FN T-score by 10% to 13%. Men in the low-LS group had very few fractures; therefore, a meaningful analyses of fracture risk could not be conducted. This study shows the significant contribution of lower LS BMD to fracture risk over and above FN BMD in women. A LS BMD lower than FN BMD should be incorporated into fracture risk calculators at least for women in older age-groups.

Epidemiology of Vertebral Fractures

Vertebral fractures are one of the most common fractures associated with skeletal fragility and can cause as much morbidity as hip fractures. However, the epidemiology of vertebral fractures differs from that of osteoporotic fractures at other skeletal sites in important ways, largely because only one quarter to one-third of vertebral fractures are recognized clinically at the time of their occurrence and otherwise require lateral spine imaging to be recognized. This article first reviews the prevalence and incidence of clinical and radiographic vertebral fractures in populations across the globe and secular trends in the incidence of vertebral fracture over time. Next, associations of vertebral fractures with measures of bone mineral density and bone microarchitecture are reviewed followed by associations of vertebral fracture with various textural measures of trabecular bone, including trabecular bone score. Finally, the article reviews clinical risk factors for vertebral fracture and the association of vertebral fractures with morbidity, mortality, and other subsequent adverse health outcomes.

What analytic method should clinicians use to derive spine T-scores and predict incident fractures in men? Results from the MrOS study

In this study, the area under the curve was highest when using the lowest vertebral body T-score to diagnose osteoporosis. In men for whom hip imaging is not possible, the lowest vertebral body T-score improves the ability to diagnose osteoporosis in men who are likely to have an incident fragility fracture.

INTRODUCTION

Spine T-scores have limited ability to predict fragility fracture. We hypothesized that using lowest vertebral body T-score to diagnose osteoporosis would better predict fracture.

METHODS

Among men enrolled in the Osteoporotic Fractures in Men Study, we identified cases with incident clinical fracture (n = 484) and controls without fracture (n = 1,516). We analyzed the lumbar spine bone mineral density (BMD) in cases and controls (n = 2,000) to record the L1-L4 (referent), the lowest vertebral body, and International Society for Clinical Densitometry (ISCD)-determined T-scores using a male normative database and the L1-L4 T-score using a female normative database. We compared the ability of method to diagnose osteoporosis and, therefore, to predict incident clinical fragility fracture, using area under the receiver operator curves (AUCs) and the net reclassification index (NCI) as measures of diagnostic accuracy. ISCD-determined T-scores were determined in only 60 % of participants (n = 1,205).

RESULTS

Among 1,205 men, the AUC to predict incident clinical fracture was 0.546 for L1-L4 male, 0.542 for the L1-L4 female, 0.585 for lowest vertebral body, and 0.559 for ISCD-determined T-score. The lowest vertebral body AUC was the only method significantly different from the referent method (p = 0.002). Likewise, a diagnosis of osteoporosis based on the lowest vertebral body T-score demonstrated a significantly better net reclassification index (NRI) than the referent method (net NRI +0.077, p = 0.005). By contrast, the net NRI for other methods of analysis did not differ from the referent method.

CONCLUSION

Our study suggests that in men, the lowest vertebral body T-score is an acceptable method by which to estimate fracture risk.

Use of lowest single lumbar spine vertebra bone mineral density T-score and other T-score approaches for diagnosing osteoporosis and relationships with vertebral fracture status

For diagnosing osteoporosis, International Society for Clinical Densitometry guidelines suggest using the lowest bone mineral density T-score of the lumbar spine (LS), femoral neck (FN), or total hip (TH). For the LS, use of the total spine (L1-L4) T-score is suggested. Although controversial, some authors have suggested using a single lumbar vertebra of L1-L4 with the lowest T-score to diagnose osteoporosis. We compared the ability of various T-score approaches [lowest single LS vertebra of L1-L4; total spine; FN; TH; and the lowest T-score of total spine, FN, or TH to diagnose osteoporosis in 2560 postmenopausal women from the Multiple Outcomes of Raloxifene Evaluation trial placebo group. The discriminatory ability of each T-score approach to identify women with or without vertebral fracture was compared using the area under receiver-operating characteristic curve. When the lowest single LS T-score of L1-L4 and the total spine T-score were used, 77% and 57% of women were categorized as having osteoporosis, respectively. These T-score approaches had similar ability for discriminating between women with or without prevalent vertebral fractures and for predicting the risk of incident vertebral fractures. The lowest single LS vertebra T-score identified a greater proportion of women with osteoporosis than currently accepted approaches. Thus, the WHO diagnostic classification should not be applied to single vertebral T-scores. This analysis supports the current International Society for Clinical Densitometry position to use the total spine T-score for osteoporosis diagnosis.

Vertebral Fracture Assessment: the 2007 ISCD Official Positions

Vertebral fracture assessment (VFA) is an established, low radiation method for detection of prevalent vertebral fractures. Vertebral fractures are usually not recognized clinically at the time of their occurrence, but their presence indicates a substantial risk for subsequent fractures independent of bone mineral density. Significant evidence supporting VFA use for many post-menopausal women and older men has accumulated since the last ISCD Official Position Statement on VFA was published. The International Society for Clinical Densitometry considered the following issues at the 2007 Position Development Conference: (1) What are appropriate indications for Vertebral Fracture Assessment; (2) What is the most appropriate method of vertebral fracture detection with VFA; (3) What is the sensitivity and specificity for detection of vertebral fractures with this method; (4) When should additional spine imaging be performed following a VFA; and (5) What are the reporting obligations for those interpreting VFA images?

Discordance in diagnosis of osteoporosis using spine and hip bone densitometry

Diagnostic discordance for osteoporosis is the observation that the T-score of a patient varies between skeletal sites, falling into 2 different diagnostic categories identified by the World Health Organization classification system. Densitometrists and clinicians should expect that at least 4 of every 10 patients tested by dual-energy X-ray absorptiometry (DXA) to demonstrate T-score discordance between spine and total hip measurement sites. T-score discordance can occur for a variety of reasons related to physiologic and pathologic patient factors and the performance or analysis of DXA itself.

Radiographic texture analysis of densitometer-generated calcaneus images differentiates postmenopausal women with and without fractures

INTRODUCTION

Bone fragility is determined by bone mass, measured as bone mineral density (BMD), and by trabecular structure, which cannot be easily measured using currently available noninvasive methods. In previous studies, radiographic texture analysis (RTA) performed on the radiographic images of the spine, proximal femur, and os calcis differentiated subjects with and without osteoporotic fractures. The present cross-sectional study was undertaken to determine whether such differentiation could also be made using high-resolution os calcis images obtained on a peripheral densitometer.

METHODS

In 170 postmenopausal women (42 with and 128 without prevalent vertebral fractures) who had no secondary causes of osteoporosis and were not receiving treatment for osteoporosis, BMD of the lumbar spine, proximal femur, and os calcis was measured using dual energy x-ray absorptiometry. Vertebral fractures were diagnosed on densitometric spine images. RTA, including Fourier-based and fractal analyses, was performed on densitometric images of os calcis.

RESULTS

BMD at all three sites and all texture features was significantly different in subjects with and without fractures, with the most significant differences observed for the femoral neck and total hip measurements and for the RTA feature Minkowski fractal (p<0.001). In univariate logistic regression analysis, Minkowski fractal predicted the presence of vertebral fractures as well as femoral neck BMD (p<0.001). In multivariate logistic regression analysis, both femoral neck BMD and Minkowski fractal yielded significant predictive effects (p=0.001), and when age was added to the model, the effect of RTA remained significant (p=0.002), suggesting that RTA reflects an aspect of bone fragility that is not captured by age or BMD. Finally, when RTA was compared in 42 fracture patients and 42 nonfracture patients matched for age and BMD, the RTA features were significantly different between the groups (p=0.003 to p=0.04), although BMD and age were not.

CONCLUSION

This study suggests that RTA of densitometer-generated calcaneus images provides an estimate of bone fragility independent of and complementary to BMD measurement and age.

Skeletal sites for osteoporosis diagnosis: the 2005 ISCD Official Positions

The International Society for Clinical Densitometry (ISCD) has developed Official Positions to assist healthcare providers in addressing some of the issues inherent with the use of bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DXA) to diagnose osteoporosis, apply World Health Organization (WHO) T-score classifications, and monitor BMD changes over time. Differences exist, however, between the ISCD Official Position statement and that of the International Osteoporosis Foundation with respect to WHO criteria for skeletal sites. Consequently, a subcommittee of the ISCD was directed to address the application of the WHO classifications to specific skeletal sites and regions of interest. In 2005, the ISCD Position Development Conference reviewed the findings and prepared Official Positions, which address whether or not: (1) the lowest T-score of the total proximal femur, femoral neck, trochanter, and spine should continue to be used for diagnosis; (2) the WHO classification may be applied to a single vertebral body T-score; and (3) the ISCD should endorse the use of the National Health and Nutrition Examination Survey database for proximal femur T-score derivation. The resulting ISCD Official Positions, with their corresponding rationales and evidence are provided here, as well as questions that will need to be addressed in the future.