Bone Densitometry

Bone tissue is continuously evolving. At all times, small amounts of bone are being absorbed by your body and replaced with new bone. The amount of bone removed and replaced is about the same when you’re young and in peak health. However, as you age, this process can become imbalanced, resulting in a loss of bone structure and strength.

Everyone experiences bone density loss in their lifetime. Fortunately, the rate of progression and the severity of the effects can often be improved with early diagnosis and treatment. Physicians assess bone density through a type of testing called bone densitometry.

What Is Bone Densitometry?

Bone densitometry, more commonly known as a bone density test, is an x-ray technique used to measure the strength and density of bones. Several types of bone densitometry are in use today. Dual-energy x-ray absorptiometry (DEXA) is currently one of the most accurate methods. 

At the Orthopaedic Institute of Ohio, we use the new Lunar DPX Bone Densitometer.

What Are Some Common Uses for Bone Densitometry?

Bone densitometry is primarily used to diagnose osteoporosis, a condition that develops when bone is no longer being replaced as quickly as it is absorbed. As the bone loses density or mass, it becomes progressively weaker, and the risk that it may break increases. Osteoporosis often goes unnoticed for years, with no discomfort or other symptoms until a fracture occurs.

Bone densitometry is also effective for diagnosing other conditions that cause bone loss (such as osteopenia), tracking the progress of treatment or predicting the likelihood of fracturing a bone in the future.

Who Should Have a Bone Density Test?

Routine bone density tests may be recommended if you are at high risk for a bone loss condition. Some common risk factors for bone loss include:

• Advancing age
• Family history
• Smoking
• Excessive alcohol consumption
• Previous fracture injuries
• Long-term use of steroids
• Long-term use of certain medications
• Low BMI (body mass index)
• Certain diseases, including hyperthyroidism, rheumatoid arthritis or kidney disease
• Reduced levels of estrogen (particularly in post-menopausal women) 

What Bones Are Scanned in a Bone Density Test?

Physicians typically use bone densitometry to assess the spine and hips. Occasionally, the whole body is scanned. Smaller DEXA devices are used to evaluate the finger, hand, wrist, forearm, shoulder or heel.

How Should I Prepare Before a DEXA Scan?

This exam requires little to no preparation. Inform your physician of any health conditions you have, treatments you have recently undergone or medications you are currently taking. If you can, wear loose, comfortable clothing and leave jewelry at home. You may eat and drink normally on the day of your bone density test, but please do not take calcium supplements for at least 24 hours before the exam.

How Is a Bone Density Test Done?

OIO’s bone densitometry scans are done on an outpatient basis. Generally, the process follows these steps:

• You will remove all metal objects from your body, such as jewelry, eyeglasses and dental appliances.
• If you are allowed to wear your own clothing, you will also need to remove items with metallic elements like belt buckles and zippers.
• If you are instructed not to wear your own clothing, you will be given a gown to wear.
• You will recline on an X-ray table, lying flat on your back. 
• During the spinal portion of the scan, your legs will be supported on a cushion to help straighten your pelvis and lumbar spine.
• During the hip scan, your feet will be placed in a brace to rotate your hips inward.
• One part of the scanner will pass slowly underneath the table, while another part will pass above the table in parallel.
• You must stay very still and may be asked to hold your breath briefly to get the clearest picture.
• Bones in your extremities may be scanned depending on your physician’s request.

The bone densitometer translates the data it gathers into pictures and graphs that can then be interpreted by a trained provider. The exam causes no pain, though you may find your positioning uncomfortable, particularly if you have recently had surgery or an injury. The scan takes about 15-30 minutes.

What Can I Expect After a Bone Densitometry Scan?

There is no downtime or recovery after a bone density test. You should be able to resume your usual activities immediately with no restrictions or aftercare requirements.

Is Bone Densitometry Safe?

DEXA scans are simple, quick and noninvasive. Anesthesia is not needed, and the amount of radiation used is extremely small. No radiation remains in the body after the examination. 

Women should inform their physician or the technician performing the exam if there is any possibility that they are pregnant. 

There could be other risks depending on your specific health condition; discuss any concerns with your provider before the procedure.

How Will I Receive My Bone Densitometry Scan Result?

A radiologist will analyze the images gathered during your exam and send a report to the referring physician. Your physician will then explain the results to you and help you make decisions about how to keep your bones healthy. Early treatment is the best way to reduce bone loss, lower your risk of osteoporosis and prevent fractures.

What Information Can Be Learned From Bone Densitometry?

Bone densitometry test results are reported in two numbers: T-score and Z-score. 

T-score

Your T-score compares your bone density to what is typically expected in a healthy young adult of your sex. It shows the amount (a number of units called “standard deviations”) that your bone density is above or below the average. 

A T-score of -1 and above means your bone density is normal. A score between -1 and -2.5 indicates your bone density is below normal and may lead to osteoporosis. At -2.5 and below, your bone density is low and you likely have osteoporosis.

Z-score

Your Z-score compares your bone density to what is normally expected for someone of your age, sex, height, weight and ethnic or racial origin. It is also measured in standard deviations above or below the average. If your Z-score is substantially higher or lower than the average, your doctor may order additional tests.

How Often Should I Get a Bone Density Test?

The recommended schedule for bone density evaluations is usually once every one to two years. Your OIO healthcare team will consider your age, risk factors, previous DEXA scan results and current treatment plan. Ideally, follow-up exams should be performed at the same institution and with the same machine to ensure the accuracy of the results.

Bone densitometry is currently the “gold standard” for diagnosing osteoporosis and fracture risk. It is never too early to prioritize your bone health and set yourself up for an active life at any age. To schedule an exam or speak to a provider about steps you can take to slow bone loss, contact the Orthopaedic Institute of Ohio at 419-222-6622.