The term osteoporosis quite literally means porous bone. Normal bone marrow has small holes within it, but a bone with osteoporosis will have much larger holes that may look like a sponge. This is because the disease is a loss of bone mass; it alters the structure of the bone and causes the bones to become thinner, weaker and more apt to break. There is no cure for osteoporosis.
The disease also progresses without any warning signs until a painful fracture occurs. It would not really be feasible to take a piece of bone to examine it for any structural damage so instead a special type of X-ray technique called densitometry is used. Densitometry is the only sure way to determine bone density and fracture risk for osteoporosis. This type of bone mass measurement is also called bone mineral density or a BMD test.
The World Health Organization has established criteria for making the diagnosis of osteoporosis. These criteria are based on comparing bone mineral density (BMD) with the young adult mean. The young adult mean is defined as a healthy 30 years old. Those with bone density at 2.5 standard deviations below the mean are diagnosed as having osteoporosis.
BMD measurement is given as a T score and a Z- score. The T score is the deviation from the mean bone density of healthy young adults of the same gender and ethnicity. The Z score is the deviation from the mean bone density of adults of the same age and gender. A score of 1 to 2.5 indicates some bone loss and potential risk for osteoporosis.
This condition is called Osteopenia. Every standard deviation below normal doubles the risk for fracture so -1 standard deviation below normal equals 2 times the risk, -2 standard deviation equals 4 times, -3 standard deviation equals 8 times and so on.
There are several different types of these specialized x ray machines, or bone densitometers that measure bone density. Central machines measure density in the hip, spine and total body. Peripheral machines measure density in the finger, wrist, kneecap, shin, bone and heel.
Only recently has the FDA approved the use of bone density tests on the middle finger, shin and heel. The information obtained from a bone density test enables doctors to determine whether an individual is at risk for fracture and what, if any course of action should be taken. In general the lower ones bone density, the higher the risk for fracture.
For those at high risk of developing osteoporosis or who are concerned about their risk it may be a good idea to get a scan done before a fracture occurs so that an appropriate prevention and treatment plan can be administered.
It is important to remember that with increased age comes increased risk of osteoporosis and fracture, those who have a family history of osteoporosis or fractures, and those who have been diagnosed with certain diseases would be considered high risk and may warrant a diagnostic test as a preventive tool.