Why measure bone density ?
Bone loss occurs in many people as they age, often resulting in fractures of the hip, spine and wrist.
Severe bone loss and progressive osteoporosis most commonly occurs in caucasian and Asian women during and following their menopause (cessation of monthly periods). Nonetheless, 10% of black women over the age of 50 have osteoporosis as do 24% of white men and 17% of black men aged 80 and over.
A variety of risks may also cause premature and "silent" bone loss in premenopausal women. These factors include cigarette smoking, lack of exercise, abnormal monthly menstrual periods, a family history of osteoporosis and the use of drugs such as prednisone for asthma and arthritis, and thyroid hormones.
Scientists now know that 30-40% of bone mineral must be lost before bone loss is detectable on a routine X-ray. Therefore, specialized techniques have been developed to detect small amounts of bone loss in those people at risk. The most widely available and preferred technique is Dual Energy X-ray Absorptometry or DEXA, for short.
How is bone mineral content measured?
The most recently developed and most frequently used measurement by the Bone Health Program at Barnes-Jewish Hospital is DEXA.
You can arrange for a DEXA by calling the Bone Health Program at (314) 454-7775
During DEXA, the patient lies on a padded table while a mechanical arm passes back and forth over the area being measured without touching the patient. No injections or dyes are used. The DEXA, which is a simple and fast procedure involving no discomfort, can measure bone mass in the spine, hip and wrist.
Within 5-7 minutes, the X-ray beam records the amount of calcium in the bone. A computer attached to the machine calculates the amount of bone mineral and compares it to values considered normal in people of the same age and sex as the patient.
The amount of X-ray received is minimal since it delivers only one-sixth that of a chest X-ray or the same amount a person might get from the altitude while flying from New York to Los Angeles.
Although the amount of X-ray exposure is minimal, DEXA of the hip and spine is not performed on pregnant women, as a matter institutional health policy. Measurement of the wrist bone mass may be used instead.
What can a patient expect ?
Making an appointment is easy. Just call (314) 454-7775. Appointments can be scheduled usually within two weeks.
During the first phone call, you will be asked the name of your referring physician, and other basic information about yourself. If you need a referral from your insurance company, make sure you take care of that before your appointment.
You do not have to prepare anything special for the DEXA. Keep to your normal diet and daily routine. You will not need to disrobe, have your temperature taken or be given any injections.
The Bone Health Program is located on the sixth floor of the Steinberg Building at Barnes-Jewish Hospital north, immediatly when you get off the elevator. The whole DEXA takes 20 minutes from start to finish, including filling out any other required forms.
Should I wear anything special ?
To make the examination easier, we recommend that you wear loose-fitting comfortable clothing, such as sweat shirts and sweatpants with no zippers, buttons, safety pins or other metal or plastic fasteners.
If this is not convenient or you forget, don't worry, you can slip into clean hospital scrubs provided at the Bone Health private dressing rooms.
Will the doctor be there while I take the DEXA?
In most cases, a trained DEXA technician administers the DEXA. He or she will explain the procedure to you. The specialist physicians at the Bone Health Program will interpret the results and submit a report including detailed measurement data to your physician within a few days. If your situation is different, and you need a physician present or a report provided immediately, tell the person scheduling your DEXA.
What is the benefit of this test?
DEXA provides a safe, inexpensive and accurate means of measuring bone density. Similar to a baseline mammogram, the initial DEXA provides a baseline measurement or point of comparison for future measurements, thereby identifying the degree of bone loss, if any.
Repeated measurements at one to two year intervals determine an accurate rate of loss and effectively monitor the result of treatment. DEXA also helps physicians assess the likelihood of developing fractures. For example, more than 30% loss of bone mass in the hip leads to a significatn increase in the fracture rate.