Osteoporosis: A debilitating disease that can be prevented and treated.
Osteoporosis is a disease in which bones become fragile and more likely to break. If not prevented or if left untreated, osteoporosis can progress painlessly until a bone breaks. These broken bones, also known as fractures, occur typically in the hip, spine, and wrist. Any bone can be affected, but of special concern are fractures of the hip and spine. A hip fracture almost always requires hospitalization and major surgery. It can impair a person’s ability to walk unassisted and may cause prolonged or permanent disability or even death. Spinal or vertebral fractures also have serious consequences, including loss of height, severe back pain, and deformity. Millions of Americans are at risk. While women are four times more likely than men to develop the disease, men also suffer from osteoporosis. What is the relationship between BMD and fracture risk?
In subjects with low bone mass (as defined above), there is a 2 to 3 fold increase in the incidence of spinal fractures. In subjects with a BMD in the osteoporosis range, there is approximately a 5 times increase in the occurrence of fractures.
Who should have BMD testing?
At present, the National Osteoporosis Foundation has recommended that testing be performed on all postmenopausal women under the age of 65 who have risk factors for osteoporosis (these include a previous history of fractures, low body weight, cigarette smoking, and a family history of fractures). In addition, it is recommended that all women over the age of 65 be tested, regardless of risk factors. It is also advised that anyone seeking therapy for osteoporosis be tested. These are guidelines only, and it should be remembered that testing is only indicated if it will influence treatment decision. For example, is the patient willing to be treated if the results are positive?
How is BMD measured?
Dual X-ray absorptometry (DXA) is the preferred technique for measuring BMD. [DXA is also called dual energy X-ray absorptometry or DEXA.] DXA is relatively easy to perform and the amount of radiation exposure is low. A DXA scanner is a large machine that produces 2 x- ray beams, each with different energy levels. One beam is high energy while the other is low energy. The amount of x-rays that pass through the bone is measured for each beam. This will vary depending on the thickness of the bone. Based on the difference between the 2 beams, the bone density can be measured. At present, DXA scanning focuses on 2 main areas — the hip and spine. Because osteoporosis involves the whole body, measurements of BMD at one site are usually predictive of fractures at other sites. However, by directly measuring the areas of particular interest, such as the hip and the spine, a direct observation can be made. For example, hip measurements provide a better prediction of hip fracture risk than measurements taken at other skeletal sites. In general, DXA scanning is performed on the hip (including an area of the femur called the “Wards triangle”) and the spine. Scanning generally takes 10 to 20 minutes to complete. Older techniques used a single beam x-ray that worked well for sites such as the wrist. However, to measure the hip, a single beam is not optimal since there is so much surrounding tissue. Single energy sources cannot correct for variations in soft tissue thickness, so their use is limited. Another older technique known as dual photon absorptometry (DPA) works on the same principles as DXA. However, it is slower and requires a larger radiation exposure.
Please consult with our physician if you feel that you may be at risk.