Osteoporosis and Dexa Scanning
Osteoporosis is a major public health concern. It affects more than 25 million American men and women. In the United States, in the year 2000 an estimated 5.2 million hip, spine, and forearm fractures will occur among white women age 45 years and older, with projected direct medical costs of approximately $45.2 billion. Women age 65-84 years old will experience the greatest number of fractures, and most of these fractures are secondary to postmenopausal (involutional) osteoporosis, also called primary osteoporosis.
Primary osteoporosis exists if no known secondary cause of bone disease can be identified by x-ray, clinical and/or laboratory data. Sometimes primary osteoporosis will occur in a young individual, but this is the form of bone disease seen mostly in elderly men and women. Of course, women are more at risk for the development of osteoporosis for several reasons:
- Women have a relatively lower peak bone mass
- Women are generally smaller than men
- Women’s bone loss is accelerated at the menopause
- There are gender-related geometric and architectural differences in the bone of men and women
- Women generally live longer than men
Secondary osteoporosis is related to an underlying medical condition or even to agents/medications. Some recognized causes of secondary osteoporosis include:
- nutritional/diet related-calcium or vitamin D deficiency
- alcoholism
- endocrine diseases
- disuse-immobilization
- drugs-steroids
- anticonvulsants
- other diseases-chronic illness
- malignancy
- kidney disease
- inherited diseases
Measuring Bone Mineral Density
Despite extensive research on bone metabolism and physiology, and despite advances made in understanding the interaction of estrogen, calcium, vitamin D, and other chemical modulators of bone density, guidelines have not been definitively validated for the most efficient, cost effective approach toward evaluation of patients who have or are suspected of having low bone mineral density. Unfortunately, most cases of osteoporosis are diagnosed after a fracture has occurred. A typical presentation would be, for example, an elderly woman who has onset of severe back pain due to vertebral compression fractures (fragility fractures), or severe pelvic pain due to a spontaneous pelvic rim fracture. In most cases, these women are found to have well-established osteoporosis. In other instances, patients (usually women) will present themselves to their physician concerned about the development of osteoporosis, especially if they fall into a high risk category.
An international group of experts under the auspices of the World Health Organization has suggested that the best way to diagnose osteoporosis before fractures is to measure bone mineral density. (1994)
Dual-Energy X-ray Absorptiometry
Dual energy x-ray absorptiometry (DEXA) is an accurate and widely used technique to measure bone mineral density (BMD). DEXA is a safe, accurate, and precise technique to assess the mineral content of the skeleton. It is a noninvasive procedure. Compared with other scanning techniques, it has low radiation exposure.
As mentioned, clinical indications for measuring bone mineral density have not been standardized, but various researchers in the field, along with organizations such as WHO and the American College of Physicians have suggested the following clinical indications for bone densitometry:
- Presence of strong risk factors
- Premature menopause (under 45)
- Prolonged secondary amenorrhea
- Family history of osteoporosis
- Low calcium intake
- Corticosteroid therapy
- Prolonged immobilization
- Other conditions associated with bone loss
- Radiographic evidence of vertebral deformity or osteopenia
- Previous fragility fractures
- Deciding on estrogen replacement therapy at the time of menopause
- Monitoring osteoporosis therapy
Concluding Remarks
Osteoporosis is now recognized as a major health concern, as well as the cause of significant morbidity and mortality in the population as men and women age. Osteoporosis is treatable, and recent evidence suggests that it is preventable. Together with a complete medical history, appropriate physical examination, and laboratory and radiologic diagnostic testing, the DEXA completes a thorough evaluation for osteoporosis.
Authored by: Carolyn Smith, M.D.