Bone Density

Bone Density

What is Osteoporosis?

Osteoporosis is a condition in which bones lose calcium, become fragile and tend to break more easily. Osteoporosis afflicts one in two females over the age of 60 and one in three males over the age of 60 in Australia. The hormonal changes that accompany menopause accelerate the loss of calcium. Your bones comprise a hard outer shell covering a less dense tissue resembling honeycomb. When osteoporosis develops the outer bone 'shell' becomes thin and weak and the 'honeycomb' develops larger holes, weakening the bones and increasing the risk of fractures.

Measuring Bone Density

Low bone density is the greatest risk factor for spine and hip fractures. The most common cause for loss of bone density is osteoporosis. The key to preventing osteoporosis is early detection, diagnosis and treatment.

The association between low bone density and osteoporotic fracture is similar to the association between cholesterol and heart disease or blood pressure and stroke. Like cholesterol levels and blood pressure, bone density is a risk factor that can be changed. Low bone mass can be diagnosed, prevented and treated. This technology also provides an excellent tool for assessing the skeletal body fat changes during weight loss therapy, exercise programmes, in endocrine and growth disorders and has paediatric and sports medicine applications.

Dexa Scanning

The machine that is used to measure bone density is called a Dexa machine. DEXA stands for dual energy x-ray absorptiometry. Low dose x-ray of two different energies are used to distinguish between bone and soft tissue giving a very accurate measurement of bone density

Preparation for the test

There is no specific patient preparation. You will be asked to remove anything with buttons, buckles or zips (metal) from the waist down (you may like to wear elasticized jogging pants for the examination). You will be asked to lie on a flat, padded comfortable couch. The procedure is painless and non invasive. The examination is carried out while you lie still on your back and takes about 15 minutes.

A thin beam of x-ray energy is passed through the lower hip and spine regions. A computer calculates how much x-ray energy is being absorbed by the bones and calculates the results for what is expected for a person of your age, sex and race. This is then interpreted by a specialist doctor. The x-ray dose you are exposed to is extremely low and similar to what you would receive on a long distance air flight.

Bone Scan and DEXA Scan

The two are often confused. A DEXA scan measures bone density and diagnoses osteoporosis whereas a bone scan is a nuclear medicine study used to look for stress fractures, cancer and bone and joint problems.


  • Early detection and intervention is crucial
  • 50% of women over the age of fifty will have some type of osteoporotic fracture in their lifetime
  • 50% of the people suffering an osteoporotic hip fracture will not walk again
  • The risk of death from osteoporosis in women equals the risk of death from breast cancer
  • Osteoporosis leads to 1.5 million fractures each year. Bone mineral densiometry is the only practical way to detect low bone mass
  • One third of Caucasian women over the age of 50 are at high risk of osteoporosis
  • In Australia a person is hospitalised for an osteoporotic fracture every 8.1 minutes