Bone density testing screens for risk of osteoporosis.

Osteoporosis is a disease where bones become fragile and more likely to break or fracture due to loss of bone density. Any bone can fracture. As we age, a greater concern for fractures of the hip and spine may be warranted. A hip fracture may require major surgery that can cause prolonged disability and even death. Spinal fractures can result in loss of height, severe back pain, and deformation.

For additional information on osteoporosis, including risk factors, prevention and treatment, please visit the National Institutes of Health webpage entitled:

Osteoporosis and Related Bone Diseases

FAQ's about bone density testing.

Scroll down the page to read the answers, or click on a question and you will be taken directly to the answer.

• What equipment is used for the test?
• How does the Achilles test unit work?
• What does the test feel like?
• How long does the test take?
• How are the test results presented?
• How is the T-score interpreted?
• How is the Z-score interpreted?
• How is the Results Graph interpreted?

In the past, screening for osteoporosis has been performed through a relatively costly and time consuming procedure called Dual-Energy X-Ray (DEXA). With the advent of ultrasound, it is now possible to measure bone density with a small, portable ultrasound unit designed exclusively for bone density testing.

Northwest Wellness uses the highly advanced Lunar Achilles Express. It is superior to other ultrasound systems because it uses a thermally controlled water coupling and stationary sensors. These features and their importance are explained below.

Achilles test results are comparable to DEXA. If you would like to view additional information from the manufacturer, please click on the following links:

The Achilles measures the bone density of the heel. The heel is used because its structure provides measurements comparable to DEXA measurements of the hip and spine.

Using high frequency sound waves, the Achilles Express measures both the speed of sound and broadband ultrasound attenuation. This means that it analysis the density of the bone by measuring both how fast sound travels through it, and how much of the sound reaches the other side.

Ultrasound does not travel through air. If you've had an ultrasound test before, it is likely that a heavy gel was used between the sensor and the body. The gel works as an acoustic coupling through which the sound waves travel.

The Achilles uses water to obtain the best possible results. Water is not only an ideal coupling solution, but in the Achilles Product it is thermally controlled to 92° for consistent results. This is important because temperature variations can affect ultrasound measurements.

The procedure is completely non-invasive and painless. It feels like there is a warm water bottle pressing against each side of the heel.

Because the water containers must make skin contact with the back heel, you must remove any foot coverings such as socks & shoes. Women should not wear pantyhose.

The test takes about two minutes from start to finish, including printing the results.

One of the reasons the Achilles is comparatively accurate is because it uses stationary sensors. The Achilles monitors the ultrasound signals for stability. Should the patient make a significant movement, the machine will automatically restart the measurement.

Printed test results are presented to each client for their historical records and to discuss with their doctor.

Both measurements, how fast the sound travels through the heel bone and how much of the sound reaches the other side, are combined into a single index called the Stiffness Index. The Stiffness Index is an expression of bone quality relating to density, structure and strength.

The Stiffness Index is then used to create two separate scores:

1. T-score: The Stiffness Index is compared to reference figures for a healthy young adult to create the T-score.
2. Z-score: The Stiffness Index is compared to reference figures for a healthy adult in the patient's age group to create the Z-score.

Both score values appear on a computer printout presented to each patient.

The T-score indicates current risk for fracture as compared to a healthy young adult.

• The "healthy young adult" used for the reference model would obtain a T-score of 0.0.



• A T-score higher than 0.0 indicates less risk than that of the reference model.



• A T-score lower than 0.0 indicates greater risk than that of the reference model.




Risk is defined as follows:

• A score higher than -1.0 indicates low risk.
• A score between -1.0 and -2.5 indicates intermediate risk.
• A score lower than -2.5 indicates high risk.

The Z-score indicates current risk for fracture as compared to age-matched peers.

A Z-score of 0 indicates that the patient matches the age-matched reference model. A higher score indicates that the patient is at less risk, and a lower score indicates that the patient is at greater risk.

Z-score results are best interpreted by looking at the Results Graph described below.

On the Results Graph presented to each client, the T-score is indicated by an asterisk (*). The numerical value of the T-score is indicated by numbers running down the right side of the graph. The numbers range from 2 to -4.

Areas of white, light gray and dark gray indicate the placement of the T-score in the low, intermediate and high risk categories, respectively.

A downward curved Age Regression Line runs across the Results Graph from left to right. This line represents the loss in bone density experienced by the age-matched reference group. Age is indicated by numbers running along the bottom of the graph. The numbers range from 20 to 100.

A person matching the age-matched reference model, the vertical position of the T-score will correspond to the vertical position of the Age Regression Line at the point directly above the patient's age as indicated on the bottom of the graph.

A person at lower risk than the age-matched reference model, the T-score will fall above this point. Conversely, a patient at greater risk than the age-matched reference model, the T-score will fall below this point.

While test results are important indicators, they do not constitute a diagnosis.

Discuss your results with your doctor. If your doctor is not yet familiar with the Achilles, forward the information presented on this website.