Bone Abstracts

BMD alone is not sufficient to predict the fracture risk for an individual. Others parameters, such as microarchitecture play a key role in bone fragility. Several cross-sectional studies have shown the ability of TBS to discriminate fractured from healthy subjects in European populations. The aim of our study is to assess the ability of TBS, evaluated at the lumbar spine, to discriminate subjects with and without fracture in a large white US population.

We present a case–control study on white non Hispanic US women aged 40 and older. Patients who had prior exposure to corticosteroids, systemic illness or who were taking medications known to affect bone metabolism were not included. Fractured subjects had a history of at least one low energy fracture (all osteoporotic fractures). BMD was measured at the lumbar spine (L1–L4) using a Prodigy densitometer (GE-Lunar, Madison, WI, USA). TBS was calculated at L1–L4 directly on the same image as the BMD using the TBS iNsight software (Medimaps, Pessac, France). Descriptive statistics and tests of difference were used. Univariate and multivariate logistic regressions (backward) were used to investigate possible correlations between independent variables (weight, height, BMI, BMD and TBS) and the status of fracture. Odds ratio per S.D. decrease (OR) and area under the ROC curve (AUC) of discriminating parameters were calculated.

After applying the selection criteria of subjects, 2182 were eligible. This group consisted of 305 fractured subjects (age=59.7±8.3 years, BMI=25.4±3.8 kg/m²) and 1877 control subjects (age=57.4±7.3 years, BMI=25.0±3.9 kg/m²). Weak correlations were obtained between TBS and BMD and between TBS and BMI (r=0.327 and r=−0.167 respectively, P<0.01). The average value of age, weight, BMD and TBS between the control and fractured group were significantly different (P<0.0001, P=0.02, P=0.0004, P<0.0001 respectively), whereas no difference between groups is obtained for BMI and height (P>0.05). The OR per S.D. decrease and the AUC for age, BMD and TBS were presented in the table below. After adjustment for age, weight, BMD, smoking, maternal and family history of fracture, TBS remained significant (but not BMD) with an OR of 1.18 (1.02–1.35). This study confirms the potential of TBS to discriminate subjects with and without fracture and thus even after adjustment for several clinical risk factors.