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 Yaşlı Kadınlarda Osteoporozisin Değerlendirilmesinde Tibial Kemik Ultrasonografisi ile
Çift EnerjiliX-Işını Absorbsiyonu Metodunun Karşılaştırılması

Yavuz BAYKAL, Arif YÖNEM, Orhan TARÇIN, Bayram KOÇ, Bekir ÇAKIR, Bilgin CÖMERT,
Tahir ÜNAL, Fikri KOCABALKAN

Gülhane Askeri Tıp Akademisi, İç Hastalıkları Anabilim Dalı, ANKARA

 

ÖZET

Osteoporozisin tanı ve takibinde yeni bir ultrasonografi sistemi geliştirilmiş ve yapılan çalışmalarda, bu alanda en çok kabul gören metodlardan biri olan çift enerjili x-ray absorptiometri (DEXA) ile benzer sonuçlar verdiği bildirilmiştir. Bu çalışmada amacımız, kortikal kemik özelliklerini kemik ultrasonografisi ile değerlendirip, elde edilen bulguları DEXA sonuçlarıyla karşılaştırarak, aralarında bir korelasyon olup olmadığını araştırmaktı. Çalışmaya 50-75 yaşlarında (ortalama 59.4±8.5 yıl) 32 postmenopozal kadın dahil edildi. Ultrason dalgalarının kemik dokusunda iletim hızlarının ölçümü esasına dayanan kemik ultrasonografisi tibial kemiğin orta bölgesinde, SoundScan 2000 ultrasonografi cihazı (Myriad Ultrasound Systems, Rehovot, Israel) ile gerçekleştirildi. Bu ölçümle eşzamanlı olarak, DEXA metoduyla lomber 2-4 vertebralardan kemik mineral dansitesi (BMD) ölçüldü. Hastaların ultrasonik ses iletim hızlarının ortalama 3778.6±642.4 m/sn, BMD’lerinin ortalama 0.831.9±103.1 g/cm2 olduğu tesbit edildi. Her iki yöntemle yapılan ölçüm sonuçları arasında iyi bir korelasyon olduğu belirlendi (p<0.003). Sonuç olarak, kemikte ultrasonik ses dalgalarının iletim hızının ölçülmesine dayanan kemik ultrasonografisinin, bu konuda en sık kullanılan araçlardan biri olan DEXA ile uyumlu veriler sağladığını ve bundan dolayı osteoporozisin değerlendirilmesinde kullanılabilecek, radyasyona maruz bırakmayan, noninvaziv ve kolay uygulanabilir bir yöntem olduğu görüşüne vardık.

Anahtar Kelimeler: Ultrason, velosite, kemik dansitesi, çift enerjili x-ray absorptiometri

SUMMARY

Comparison of Ultrasound Velocity Measurement with Dual-Energy X-Ray Absorptiometry in The Assessment of Osteoporosis in Elderly Women

An ultrasound instrument has recently been developed for the diagnosis and monitoring of osteoporosis, having comparable results with dual energy x-ray absorptiometry (DEXA), the well established method in this field. In the present study, our aim was to evaluate the tibial cortical bone properties using ulltrasound velocity measurement and to compare its results with that of DEXA. The study group consisted of 32 postmenopausal women, aged between 50-75 years (mean, 59.4±8.5 years). Ultrasound velocity measurements were carried out using a SoundScan 2000 device (Myriad Ultrasound Systems, Rehovot, Israel) at the midtibial region of patients. At the same time with ultrasound measurement, bone mineral density (BMD) of the lumbar spine was measured by DEXA. The mean tibial ultrasound velocity measurement was 3778.6±642.4 m/sec (range 2450-4880), the BMD was 0.831.9±103.1 g/cm2 (range 0.580-0.995). There was a good correlation between tibial ultrasound velocity and BMD by DEXA results (p<0.003). As a result, we may conclude that ultrasound velocity measured along the tibial cortex is a precise, nonradiating technique for assessing bone status and correlates significantly with BMD measured by DEXA. Hence, cortical bone ultrasound velocity seems a useful tool for establishing bone status and deserves a place among devices and techniques designed to determine bone mass and quality.

Key Words: Ultrasound, velocity, bone mineral density, dual energy x-ray absorptiometry

INTRODUCTION

The risk of fracture in elderly people, especially in postmenopausal women, is inversely related to bone mass, and bone density measurements are extremely important in predicting potential fractures in such populations. Fracture risk at a particular skeletal site, such as the hip, can be accurately assessed by measuring bone mineral density at the same site. Techniques such as single and dual photon or X-ray absorptiometry (DEXA) are now well established for the noninvasive assessment of bone mineral density and fracture risk at relevant skeletal sites including the spine, hip and forearm. But all the available tecniques for the evaluation of osteoporosis measure the quantitative aspect of bone mineral density (BMD). However, qualitative factors, such as elasticity, fatigue damage, and microarchitecture, have been implicated as additional factors contributing to bone strenght (1,2).

In this respect, ultrasonic measurement of bone has recently emerged as a promising noninvasive technology for assessment of bone strenght and fracture risk. In addition, the technique is believed to reflect both qualitative and quantitative properties of bone, since the propagation of sound in bone is related to the elastic modulus and structure, as well as to the mass density (3,4). Current ultrasonic instruments measure speed of sounds or broadband ultrasound attenuation at the calcaneus or the patella and have been shown to correlate with axial BMD (5). A new mobile ultrasonic bone instrument, which measures the speed of sound at the tibial shaft, has been introduced for the assessment of bone status recently. In contrast to other current methods that measure the velocity of ultrasound waves transmitted across the bone, this new technique is capable of measuring the speed of sound along a fixed longitudinal distance of the cortical layer parallel to the bone axis, eliminating soft tissue interference.

The aim of our study was to measure ultrasound velocity in the cortical bone of elderly people, and to compare the results of this ultrasonic techniques with bone density measured by DEXA, which is an established method in the assessment of bone status.

PATIENTS and METHODS

Patients

Our study group consisted of 32 women referred to the Osteoporosis Center of Gülhane Military Medical School of Medicine between 1997-1998. Subjects were excluded from the study if they had received medical treatment for diseases affecting bone metabolism or other types of diseases affecting bone metabolism. All the patients gave informed consent before participating in the study, which had the approval of the local ethics committee. The patients’ age range was 50-75 with a mean of 59.4±8.5 years.

Ultrasound Velocity in the Tibia

Ultrasound velocity measurements were carried out using a SoundScan 2000 device (Myriad Ultrasound Systems, Rehovot, Israel). The standart measurement site was defined as the midpoint between the apex of the medial malleolus and the distal patellar apex, determined by palpation with the leg in the extended position. Ultrasound gel was applied to the skin of measurement sites to obtain good acoustic contact. The probe was moved manually across the midtibial plane, parallel to the long axis of the tibia, searching for the site with maximal speed of sound, around the tibial crest. Each measurement comprised of a series of readings (150-200 readings), lasting about 5-10 minutes. The maximum ultrasound velocity was calculated from the average of the five highest readings.

Bone Densitometry Measurement

At the same time with ultrasound measurement, bone mineral density of the lumbar vertebra (L2-L4) was measured by DEXA (Norland XR 26, Norland Scientific Instruments, Fort Atkinson). Values were expressed as BMD in g/cm2, bone mineral content (BMC) in g/cm2, T and Z-scores in % standart deviations.

Statistical Analysis

The parameters measured in this study were expressed as means ± standart deviations (SD). The data statistically processed via single regression analysis, using the SYSTAT for Windows 6.0 and Microsoft Excel and results were accepted statistically significant when p values were less than 0.05.

RESULTS

The results of the present study is presented in Table 1. The mean age of the patients was 59.4±8.5 years. The mean of the tibial ultrasound velocity measurements was 3778.6±642.4 m/sec (range 2450-4880), the BMD was 831.9±103.1 g/cm2 (range 580-995) and the BMC was 39.2±8.7. T and Z-scores of patients were, 1.88±0.54 and respectively 1.3±0.6. There was a good correlation between tibial ultrasound velocity and BMD by DEXA results (p=0.003) (Figure 1).

DISCUSSION

Since there is no way to effectively treat established osteoporosis, it is wise to take preventive measures or early treatment for osteoporosis. Currently, noninvasive diagnostic methods of various forms are used to assess bone loss at an early stage. Most diagnostic methods so far used have involved measuring BMC or BMD to check for quantitative changes in bone mass (6). However, recent evidences indicate that bone fragility is also determined by qualitative changes in bone, such as elasticity, fatigue damage and microarchitecture (7).

Ultrasound has long been used in industrial fields to study the characteristics of substances, as well as in studies on bone properties in the previous years, based on the results of studies showing that ultrasound, passing through bone, changes according to qualitative differences in addition to quantitative changes in bone. Nonetheless, it was not used until recently. Lately, however, due to developments in computer software, increased accuracy, and ease of use, ultrasound has become a useful tool in studying bone properties (8). The studies by McCarthy et al. (9) discovered a close relationship between ultrasound velocity passing through the cortical bone and bone density. It has been shown that there are close correlations between bone ultrasound velocity and bone density at each site as measured using DEXA (10,11). The advantage of ultrasound velocity measurement over the DEXA is that DEXA measures only bone mass while velocity measurement reflects bone structure and qualitative content (12). According to the data we obtained from the present study, there was a close relationship between ultrasound velocity measurement at tibial cortical bone and BMD at lumbar spine measured with DEXA.

In conclusion, the present study shows that ultrasound velocity measured along the tibial cortex is a precise, nonradiating technique for assessing bone status and correlates significantly with BMD measured by DEXA. Hence, cortical bone ultrasound velocity seems a useful tool for establishing bone status and deserves a place among devices and techniques designed to determine bone mass and quality.

REFERENCES

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  10. Foldes AJ, Rimon A, Keinan DD, et al. Quantitative ultrasound of the tibia: a novel approach for assessment of bone status. Bone 1995; 17: 363-367.
  11. Stegman MR, Heaney RP, Gustafson DT, et al. Cortical ultrasound velocity as an indicator of bone status. Osteoporosis Int 1995; 5: 349-353.
  12. Hans D, Dargentmolina P, Schott AM, et al. Ultrasonic heel measurements to predict hip fracture in elderly women-the Epidos prospective study. Lancet 1996; 348: 511-514.

ADDRESS FOR CORRESPONDENCE:

Dr. Yavuz BAYKAL

GATA İç Hastalıkları Anabilim Dalı

Etlik, ANKARA

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