Elsevier

Maturitas

Volume 31, Issue 3, 15 March 1999, Pages 221-226
Maturitas

Stiffness index identifies patients with osteoporotic fractures better than ultrasound velocity or attenuation alone

https://doi.org/10.1016/S0378-5122(99)00003-1Get rights and content

Abstract

Objectives: To compare a composite ultrasonometry variable, the stiffness index (SI), with its two component variables of speed of sound (SOS) and broadband ultrasound attenuation (BUA), in identifying post-menopausal women with low bone mineral density (BMD) and/or osteoporotic fracture. Methods: A cross sectional sample of 1217 women (mean (S.D.) age 53.9 (9.7) years) was studied. Risk factors for osteoporosis were assessed by detailed questionnaire and women with diseases, or those taking treatments known to affect bone metabolism were excluded. Women were allocated to one of four groups: pre-menopausal women (n=476), healthy post-menopausal women (n=583), post-menopausal women with low BMD (n=101), and post-menopausal women with osteoporotic fracture (n=57). An Achilles ultrasonometer was used to perform quantitative ultrasonometry (QUS) at the os calcis. The SI, calculated mathematically from SOS and BUA, was computed. Results: Analysis of receiver operating curves (ROC) between healthy post-menopausal women and post-menopausal women with low BMD but no fracture, showed that the area under the curve (AUC) for SI was significantly greater than that for BUA (P<0.001) or SOS (P<0.05). For healthy post-menopausal women compared to women with fracture, the area AUC for SI was significantly greater than that for BUA (P<0.05) or SOS (P<0.001). No significant difference was found for AUC between BUA and SOS. Conclusion: QUS variables discriminated women with low density or fracture from healthy postmenopausal controls. The SI was a significantly better indicator than BUA or SOS in this retrospective study.

Introduction

Over the past decade several non-invasive techniques based on the attenuation of radiation have been developed to quantify bone mineral density (BMD) in the axial and peripheral skeleton [1], [2], [3]. Dual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) are standard methods. These techniques are important because they predict the risk of future osteoporotic fractures [4]. However, both DXA and QCT can be costly, involve exposure to radiation, and are not readily accessible.

Quantitative ultrasonometry (QUS) of the os calcis is another method of providing information on BMD and on bone quality [5], [6], [7], [8], [9]. Numerous retrospective studies, and several prospective studies have shown that os calcis QUS predicts osteoporotic fracture [10], [11], [12], [13], [14], [15], [16], [17], and in fact is as sensitive as DXA for risk of femur fracture [16], [17].

This cross-sectional study was designed to determine the value of these QUS variables of post-menopausal women with and without a history of osteoporotic fracture. In addition we investigated the age related decline of the ultrasound variables.

Section snippets

Material and methods

A cross-sectional sample of 1217 women was recruited during routine gynecological check up at the Hamburg Institute for Endocrinology and Reproductive Medicine and the Department of Gynecology at the University of Marburg. There were 741 post-menopausal women (59.2=7.8 years) and 476 normal pre-menopausal women who averaged almost 14 years younger. The postmenopausal women were further subdivided into 583 cases with ‘normal’ BMD (above T−2.5), those with low BMD (below T−2.5) without fracture (n

Age-related decline in ultrasound variables

Almost no age dependent decline was seen in the pre-menopausal women. BUA, SOS, and SI in healthy post-menopausal women were 10.4%, 2.4%, and 21.2% lower, respectively, than in women with low spine BMD. In women with fracture compared with healthy post-menopausal women these variables were even lower 13.7%, 2.7%, and 25.7% respectively for attenuation, velocity, and stiffness index.

ROC analysis of ultrasound variables

Table 1 gives the mean, standard deviation (S.D.), coefficient of variation (CV%) and standardised coefficients of

Discussion

Numerous cross-sectional and prospective studies have quantified BMD using DXA or QCT. However, these X-ray methods are costly and not widely available. QUS of the os calcis is a radiation-free, low-cost, rapid, and easily-used technique for evaluating BMD and predicting the risk of fracture. QUS not only measures BMD, but may provide incremental information on future risk [14], [16], [17]. Many cross-sectional, and some prospective studies on QUS and fracture risk have already been reported

Conclusion

Our results using ROC analysis showed that the SI is a better discriminator of women with osteoporosis either with or without a history of osteoporotic fracture than SOS or BUA alone. If these results can be confirmed in prospective longitudinal as well as in further cross-sectional studies, SI may prove a clinically useful tool in the diagnosis of a disorder that is becoming increasingly prevalent and important as populations age.

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