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Chủ Nhật, 30 tháng 6, 2013

Ultrasound and Osteoporosis


There is an insidious nature to osteoporosis. It is a gradual loss of bone tissue that is so slow that it is usually not noticed until there is a traumatic event like a fracture. Screens exist that can predict osteoporosis and allow treatment to begin early, and one of the best screens is ultrasound based.
Quantitative ultrasound (QUS) measures the speed of sound and broad band ultrasonic attenuation of the ultrasound beam as it passes between two ultrasound transducers. QUS can become a screen that may be predict future fractures in peri-menopausal and immediate post-menopausal women, and senior citizens of both genders. Those who have low QUS values for the ankle bone, the most common bone screened, are referred for further testing, like measurements of the spine.

QUS works by measuring how the ultrasound machine beam changes as it passes through the bone. The name for this type of ultrasound is Broad Band Ultrasonic Attenuation, or BUA. QUS can also measure how quickly the ultrasound beam passes through the patient’s bone; the name for this is Speed of Sound, abbreviated as SOS.
These two readings when taken together can tell us about how bones are structured, whether or not they are elastic, and how strong they are—in short, measures of the quality of the bone. That can be compared to the bone density. Taken together, these two assessments can help doctors predict each patient’s risk of suffering a bone fracture.
The bones of the foot are used because just like the lumbar spine, as we age these bones change. Spinal changes cause the majority problems in patients with osteoporosis. In addition, QUS is a simple process, the equipment is portable, and for the patient there is no radiation exposure.

In the three-year multicenter study, 6,174 women age 70 to 85 with no previous formal diagnosis of osteoporosis were screened with heel-bone quantitative ultrasound (QUS), a diagnostic test used to assess bone density. QUS was used to calculate the stiffness index, which is an indicator of bone strength, at the heel. Researchers added in risk factors such as age, history of fractures or a recent fall to the results of the heel-bone ultrasound to develop a predictive rule to estimate the risk of fractures. The results showed that 1,464 women (23.7 percent) were considered lower risk and 4,710 (76.3 percent) were considered higher risk.
Study participants where mailed questionnaires every six months for up to 32 months to record any changes in medical conditions, including illness, changes in medications or any fracture. If a fracture had occurred, the patients were asked to specify the fracture's precise location and trauma level and to include a medical report from the physician in charge.
In the group of higher risk women, 290 (6.1 percent) developed fractures whereas only 27 (1.8 percent) of the women in the lower risk group developed fractures. Among the 66 women who developed a hip fracture, 60 (90 percent) were in the higher risk group.
The results show that heel QUS is not only effective at identifying high-risk patients who should receive further testing, but also may be helpful in identifying patients for whom further testing can be avoided.
"Heel QUS in conjunction with clinical risk factors can be used to identify a population at a very low fracture probability in which no further diagnostic evaluation may be necessary".

 Studies have shown that a combination of QUS and an inquiry about personal and familial risk factors would detect more cases of osteoporosis and had slightly better chance to predict fractures than the risk factors inquiry alone. It has also been discovered that ultrasound test alone have much better predictive value than risk factors alone. It is, however, still good clinical practice to do an overall assessment of risk for osteoporosis rather than QUS alone.

Ultrasound machine scanning, therefore, is a simple, quick, safe, portable, and inexpensive clinical test. It can provide physicians an opportunity to improve on the current method of identifying patients at risk for osteoporosis and the associated fractures.

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