Bone Densitometry (DEXA) The Knoxville Comprehensive Breast Center uses state-of-the-art bone densitometry equipment to take pictures of bones in the spine, hip and wrist. Bone densitometry is a safe, painless and a noninvasive x-ray technique used to quickly and accurately measure the density of bones. This measurement helps doctors identify people who have osteoporosis, predict someone's risk for fractures of the hip and spine, and monitor changes in bone density over time. 1. Why should I know my T-Score? 2. What does the T-Score Mean? 3. How is the T-Score measured? 4. Am I at risk for Osteoporosis? 5. What can I do to avoid the bone loss? 1. Why should I know my T-Score?
Your T-Score is an accurate way to measure your risk of fracture compared to a population of young adults. The T-Score is as accurate in predicting fracture risk as your blood pressure is in predicting your risk of stroke! Osteoporosis is a bigger health problem than many people realize, affecting an estimated 10 million Americans. Most patients have no symptoms before they fracture. The consequences of osteoporotic fractures cab be devastating, including chronic pain, limitation of movement, loss of independence, and even death. Fortunately, we now understand more about the processes leading to osteoporosis. We can diagnose it accurately and determine who can benefit from the effective treatments now available. 2. What does the T-Score Mean?
The result of the DEXA is expressed as a T-Score. This compares your bone density against those of a population of normal, healthy volunteers and accurately compares your risk of fracture to theirs. If your T-Score is 0, your bone density is the same as theirs and so is your fracture risk. If your T-Score is -1, your bone density is about 10% less than theirs and your overall fracture risk is twice as great as theirs. 3. How is the T-Score measured?
The T-Score is calculated from measurements done by bone densitometry. The current method is called "dual x-ray absorptiometry," or DEXA for short. This technique is far more sensitive to bone loss than regular x-ray. Although there are many devices on the market designed to be used conveniently on wrists, fingers, and heels, they can only measure peripheral sites on the body, not the central sites that a DEXA table can measure. The central sites (hip, spine) are important clinically and more predictive of global fracture risk. Central DEXA is the only approved method for follow-up measurements to monitor treatment. Although the WHO (Wolrd Health Organization) data assessing the relative fracture risk applies only to postmenopausal Caucasian women, the densitometry data is helpful in assessing bone loss in other groups at risk for bone loss.
WHO Criteria for Osteoporosis in Women
T-Score
Bone Density Relative to Normal
Relative Fracture Risk
0
Same
Same
-1.0
10% less
2 times greater
-1.5
Low Bone Mass (Osteopenia)
-2.0
20% less
4 times greater
-2.5
Osteoporosis
-3.0
30% less
8 times greater
4. Am I at risk for Osteoporosis?
The largest population at risk for osteoporosis is postmenopausal women, who start a rapid loss of bone at menopause. Men's bone loss begins later and is more gradual, but eventually can also lead to osteoporosis. There is a lot of genetic variation, with people of Northern European and Asian descent at highest risk. People with a family history of osteoporosis, skeletal deformities like scoliosis or previous nontraumatic fractures are at a higher risk. Other risk factors include dietary deficiency of vitamin D and/or calcium, gastrointestinal diseases resulting in malabsorption, and alcoholism. Endocrine conditions including diabetes, hypogonadism, hyperparathyroidism, and excessive thyroid hormone replacement or thyrotoxicosis can speed bone loss. Glucocorticoid medication (often taken for asthma or certain types of arthritis), certain anticonvulsants and certain diuretics accelerate bone loss. 5. What can I do to avoid the bone loss?
The best protection is to develop a healthy skeleton by age 20 and maintain it to age 40 and beyond by proper diet and weight-bearing exercise. Not smoking and not abusing alcohol are further preventive measures. Daily dietary calcium intake should increase from 1,200 to 1,500 mg at menopause, and dietary vitamin D should be 400 to 800 I.U. per day.
