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Orthopedic surgeons uniquely positioned to identify patients with osteoporosis
John D. Kaufman, MD, recommends training staff to be alert for patients with risk factors.
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Douglas W. Jackson, MD: Which risk factors should alert the orthopedist to evaluate a patient's bone density?
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John D. Kaufman, MD: The orthopedic surgeon is in a unique position to identify patients with osteoporosis. We are frequently the first and often the only physician to see the fracture patient. We must make every effort to determine if an injury is a fragility fracture so the patient can be treated to prevent future fractures. Since being a postmenopausal woman is a major risk factor, any woman older than 50 seen in the office or clinic with a fracture should have a bone density test. One fragility fracture greatly increases future fracture risk. Other important factors to look for include Caucasian or Asian ethnicity, thin/small build, a family history of osteoporosis, smoking, and use of certain medications especially corticosteroids. Advanced age itself increases fracture risk independent of bone density so the very old often need to be treated more aggressively.
Always take an accurate weight and height measurement and routinely ask women about height loss. Many women don't realize they have lost height. A loss of 1-1/2 inches or more should be an alert sign. Two thirds of all vertebral compression fractures are asymptomatic so take spine X-rays of any patients with a significant height loss or an excessive thoracic kyphosis.
Twenty percent of osteoporosis patients are men. Men tend to be older and more likely to have secondary factors. Be alert to any man older than 65 with fractures or other risk factors. Implement an office-wide system to ensure that skeletal health is addressed at each office visit by training office staff to be alert for patients with risk factors.
Jackson: How reliable are office roentgenograms for establishing a demineralization problem?
Kaufman: Demineralization becomes visually apparent only after 40% of bone density is lost. In spine X-rays the loss of the horizontal trabecular pattern may be an early alert sign as the horizontal trabecula are broken down before the vertical. This can often be seen on a clear lateral view of the spine. Hip X-rays may show a thinning of the calcar or a loss of normal trabecular patterns. Plain X-rays can be prone to misinterpretation, however, due to extrinsic factors such as film exposure or patient obesity. Demineralization on plain X-rays, therefore, is generally seen only in more advanced bone loss cases. X-rays will usually not help diagnose early osteoporosis and may not be reliable in deciding whether to send the patient for a bone density test.
Jackson: What site selection is best for BMD testing?
Kaufman: BMD testing is best done at the hips and the spine. This is known as "central" BMD testing. These sites are advantageous as they are usually where the most serious fractures occur. The spine is metabolically active and changes due to pharmacologic treatment can be detected earlier here.
In fact, the spine will usually show bone loss patterns in early postmenopausal women before this loss can be detected at other sites. In patients older than 60 years, however, degenerative spinal changes will frequently increase the bone density; the hip becomes a more accurate site in the older age group.
If the hip or spine cannot be measured due to metal hardware or other artifacts, then the forearm is an alternate site. The forearm is an especially good site when evaluating patients for hyperparathyroidism as cortical bone density changes can be measured more easily here.
Peripheral BMD measurement such as at the wrist or the heel can also be a good fracture risk predictor. Peripheral BMD testing machines are portable and less expensive. The sites they measure, however, do not respond rapidly to drug actions, and they are not as accurate in monitoring treatment. A normal BMD at one site does not preclude a low BMD at another, especially in patients with multiple risk factors. At least two sites should always be measured and low bone density at multiple sites may indicate an increased fracture risk.
Jackson: Which quantitative testing is the most and least accurate?
Kaufman: Dual energy X-ray absorptiometry (DXA) of the hip and spine is considered the "gold standard" for bone density testing today. It is highly accurate and reproducible. It can be used on multiple sites and its precision is good enough to monitor response to treatment over time. The machines can be set up in an 8" × 10" room, and the test can be completed in about 10 minutes. Although DXA uses X-ray to determine BMD, the radiation amount is extremely low.
Quantitative computerized tomography (QCT) is also very accurate. This test is done using a standard CT scanner with special software available for the spine only. Its advantage is that it can determine a true volumetric bone density exclusively of trabecular bone.
By bypassing the posterior spinal elements it leaves out the sclerotic portions of an arthritic spine and can give more accurate spine results in older patients. The volumetric nature of this test also has advantages in pediatric BMD testing. QCT, however, exposes the patient to more radiation than DXA and is more expensive.
Newer central DXA devices will measure the BMD at both hips and provide a mean value. This is probably more accurate than testing one hip alone. The least accurate methods are the peripheral testing techniques that test only one site and the qualitative methods.