Table of Contents
Your Complete DEXA Guide
This post teaches you everything you need to know about DEXA scans. After reading this, you will be in a better position to ask your physician the right questions and make informed decisions.
I will explain what a DEXA scan is, walk you through how to prepare for the examination, describe what will likely happen during the examination, identify any risks, and provide insight into how to interpret the results of the DEXA scan.
At the end of this DEXA scan guide, there is a case study of a patient of mine who completed several DEXA scans. You will learn that a careful review of the results is critically important.
In this article I use the terms DEXA scan and Bone Density Test interchangeably.
How I Use the DEXA Scan
I always review the DEXA results with my clients. The information it provides is not only useful to them, but it gives me considerable insights into the health of their bones. This is especially true if the client provides DEXA tests over a period of several years.
Often, I use the data from the DEXA in the FRAX Calculator to gain insight into the patient’s fracture risk.
When your physician wants to understand the health of your bones, the starting point is the DEXA scan. They will schedule a DEXA examination at a medical imaging facility and review the results with you.
A Radiologist, a specialist in medical imaging, uses a DEXA scan examination to interpret the health of your bones. The DEXA scan report is shared with your physician.
If the results indicate you have osteoporosis, osteopenia or low bone density, your physician uses these results to recommend an appropriate treatment protocol for you.
The recommendations could include a combination of therapeutic exercises, modifications of activities of daily living, changes to your nutrition and, possibly, pharmaceutical intervention.
Given the important role that a DEXA scan examination plays in the decisions and recommendations that health professionals make, it is critical that the DEXA scan results accurately represent the health of your bones.
In the majority of instances, you should not have to worry. The medical team responsible for your DEXA scan will do an excellent job. However, DEXA scans can get confusing and it helps for you to have a general idea on what is involved in the process. Let’s get into that!
What is a DEXA Bone Density Scan?
DEXA is an abbreviation of Dual Energy X-ray Absorptiometry. DEXA is a medical imaging technology that measures the bone mineral content or density of your bones. Bone mineral density is a reliable predictor of fracture risk.
The Central DEXA measures bone density of the proximal femur in the hip and pelvis, and lumbar spine in the back. It is the method most preferred by clinicians.
A Peripheral DEXA evaluates the bone mineral density in the forearm, the heel bone (or calcaneus), the wrist and the hand. Some clinicians include this test during the examination.
In general, the medical community considers the Central DEXA a more accurate representation of bone mineral density and a better indicator of fracture risk compared to the Peripheral DEXA. While a study in 2017 challenged that position, the current consensus is to rely upon the Central DEXA results. (1)
In 1987 DEXA scanners entered routine clinical practice. (2) In 1990, a group interested in the use and interpretation of bone mineral testing started.
In 1993, a group of clinicians formed the Society for Clinical Densitometry. They changed their name to the International Society for Clinical Densitometry in 1997 and their mission is “to advance excellence in the assessment of skeletal health.” This Society oversees international training and standards for DEXA testing.
In 1997, a group of clinicians taught the first bone densitometry course in Toronto, Canada. Certification exams became available across the US just over a decade later in 2008.
A Bone Densitometry Technologist or medical imaging professional trained by a recognized institution administers the DEXA scan.
To perform a DEXA in most jurisdictions, the clinician has to have either:
- Two year undergraduate training in medical imaging sciences.
- Four year degree in medical imaging sciences.
- The Certified Bone Densitometry Technologist (CBDT®) professional certification.
Most clinicians maintain credentials through ongoing continuing education courses and testing. A number of jurisdictions have standardized accreditation tests for both the technologists and the institutions that offer DEXA scans to the public.
For example, in Canada, where I live, the Ontario Association of Radiologists manages the Canadian Bone Mineral Densitometry (CBMD) Facility Accreditation program “to ensure that accredited sites provide the highest standard of BMD services in Canada”.
The CBMD “Accreditation signifies to the public that the facility BMD equipment, BMD technologists and the services they provide, and the physicians reporting DXA scan results have met the rigorous standards set by the CBMD Program.”
Accreditation under the program is for a five year period and requires that technologists complete and pass a standardized test called the Bone Densitometry Precision Calculator.
Where Can You Get a DEXA Scan?
When you have to take your DEXA, I encourage you to visit medical imaging facilities accredited by a recognized medical body such as a national Radiologists association.
The Ontario Association of Radiologists publishes a list of CBMD accredited medical imaging institutions on its website for the public.
The American College of Radiologists (ACR) publishes a directory of ACR-accredited facilities qualified to conduct DEXA scans.
Can Untrained Individuals Perform DEXA Scans?
As I mentioned earlier in my article, your Radiologist and primary care physician make important decisions and recommendations based on the results of a DEXA scan. A proper DEXA scan will generate accurate and meaningful results.
As a result, it is important that you complete your DEXA scan with a qualified and accredited medical imaging institution.
Who Interprets DEXA Tests?
A Radiologist reviews and signs the DEXA report. A Radiologist is a physician who undergoes four years of training on medical imaging after medical school.
Radiologists who interpret DEXA results complete specialized training on bone density and DEXA.
The Radiologist will prepare a report which will be sent to your primary care physician. You should allow a space of two weeks before visiting your physician in order to discuss the DEXA scan bone density test results.
I have seen instances where a bone density test (DEXA scan) generates what looks like strange, inconsistent and hard to understand results. Individuals have high bone density test results scores in one area of their body and low results in other parts. This is not unusual among people who have been very active in certain sports and activities. Let me explain in the next sub section.
Bone Building is Site Specific.
The effect of exercise on bone is specific to area stressed during the exercise. If you want stronger leg bones, then brisk walking, squats and lunges will help. But if you want stronger arm bones, use the bones and muscles in your arms by performing arm–specific exercises such as push-ups or bicep curls.
Studies have shown that bones in the right arm of a right–handed tennis player have a greater density than bones in the left arm of the same player.
This means that if you want a stronger body, you should have an exercise program that targets as many muscles and bones as possible. This is a special feature of the Exercise for Better Bones program. You get a progressive strength-training program that covers fourteen different exercises — that gradually builds over twelve weeks. The exercises specifically target the areas most commonly affected by low bone density.
Exercise Recommendations for Osteoporosis
Exercise is an essential ingredient to bone health. If you have osteoporosis, therapeutic exercise needs to be part of your osteoporosis treatment program.
But what exercises should you do and which ones should you avoid? What exercises build bone and which ones reduce your chance of a fracture? Is Yoga good for your bones? Who should you trust when it comes to exercises for osteoporosis?
A great resource on exercise and osteoporosis is my free, seven day email course called Exercise Recommendations for Osteoporosis. After you provide your email address, you will receive seven consecutive online educational videos on bone health — one lesson each day. You can look at the videos at anytime and as often as you like.
I cover important topics related to osteoporosis exercise including:
- Can exercise reverse osteoporosis?
- Stop the stoop — how to avoid kyphosis and rounded shoulders.
- Key components of an osteoporosis exercise program.
- Key principles of bone building.
- Exercises you should avoid if you have osteoporosis.
- Yoga and osteoporosis — should you practice yoga if you have osteoporosis?
- Core strength and osteoporosis — why is core strength important if you have osteoporosis?
Enter your email address and I will start you on this free course. I do not SPAM or share your email address (or any information) with third parties. You can unsubscribe from my mail list at any time.
How Does a DEXA Scan Work?
During the DEXA scan examination the technician places you in a supine position on the table part of the DEXA machine. Your knees will be flexed and shins elevated. This position decreases the lumbar lordosis and flattens the spine against the table.
The X-ray tube (the generator) that generates the photons is behind you and the screen that captures the photons (the target) that pass through your body is located in front the abdomen. This allows the DEXA machine to measure the bone mineral density in L1 through L4 in the spine. (3)
To measure the bone density of the proximal femur (in the hip area), the DEXA technician will have you abduct and internally rotate your leg. If the leg is not adequately abducted and rotated, the bone density measurement of the femoral neck will likely not be accurate. (3)
Like the test for BMD in the spine, the generator in the DEXA scan machine will generate the photons that will pass through your hip and pelvis area and hit the target. The photon count will indicate the density of the bone mass in your femoral neck area.
The effect is similar to sunlight passing through curtains and hitting the floor of a room. The denser the curtain and the closer the lats, the less light that passes through and shows on the floor. In your case, the denser the bone, the fewer photons that pass through your body and arrive at the target.
[DEXA Machine photo attribution: Nick Smith photography [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]]
The DEXA Scan Procedure
The technologist will usually measure two areas of the body:
- Above the pelvis, specifically the lower back (known as the lumbar spine).
- Below the pelvis, specifically the thigh bone (known as the proximal part of the femur).
If you have had surgery in either of these two areas in the past, the medical professional may perform the measurement on one your forearms, also known as a Peripheral DEXA (defined above).
In cases where the patient has had surgery to the back and both of the hips, the medical professional may consider acquiring a bone density test of the whole body, where applicable. This mode is also of choice for the younger population — for example, children and teens.
During the bone density test procedure, you will need to lie on your back on a padded table. You will be kept in a comfortable position until the DEXA scan is complete and you should remain as still as possible during the measurement. You will not have to hold your breath.
In most cases the facility will measure the bone density of one hip (femoral neck). If your health insurer provides coverage for a measurement of the second hip, the facility will record the second hip as well.
Height Loss Measurement and Computation
During your visit, the staff will not only measure your bone densitometry, they will carefully measure your height without your shoes on.
Height loss can be an important indicator of fractures of the spine. As a result, height measurements should be taken each time you have a Central DEXA.
A clinician measures height loss either with Historical Height Loss (HHL) or Prospective Height Loss (PHL).
Prospective Height Loss (PHL)
The Prospective Height Loss (PHL) calculates the difference between two measurements of your height taken during a period of up to three years. In this case, the clinician has two accurate points to measure height decline.
A PHL score greater than two centimetres suggests a new vertebral compression fracture. The data is based on studies of women but can be applied to men.
Historical Height Loss (HHL)
The Historical Height Loss (HHL) is used by a clinician when there is no exact measurement of the client’s height in past years. In this case, the clinician will use the recalled height and compare it to the current height.
How Long Does a DEXA Scan Take
The duration of the Central BMD DEXA scan procedure is relatively short, however, you should allow fifteen to twenty minutes from the time you walk into the room until you leave — just to be safe.
What Will a DEXA Scan Tell You?
The report presents your bone mineral density results in three ways:
- Bone mass in grams per cm square.
- T-score: a calculation made from the DEXA manufacturer comparing your bone mass to that of their healthy control group.
- Z-score: a calculation made from the DEXA manufacturer comparing your bone mass to that of your peers.
How Accurate is DEXA Scan?
Like most measurement technologies, the DEXA is subject to some degree of error. While they are generally accurate when it comes to measuring bone density, several factors can influence the degree of accuracy. Let’s discuss these in detail.
Osteoarthritis can affect your DEXA scan in several ways. First, if you have osteoarthritis of the spine, it will cause the cartilage to deteriorate. This will create pits and spaces around the joint, giving it a rough texture. This rough texture can affect the photons as they pass through the spine.
Second, if you have arthritis in the hip, it can reduce your range of motion and limit your ability to internally rotate your leg. As you recall, this internal rotation is required to measure bone mineral density in the femoral neck.
A compression fracture in the spine can cause the spinal body to collapse. This will make the bone in the spine appear denser than it really is and lead to an inaccurate reading.
Age and Mobility
I mentioned earlier in the post that the technician will ask you to move into various positions when you are on the examination table. You will also have to flex your knees and flatten your back.
Some people can find these movements a challenge. This is especially the case for older individuals who are less mobile than they were in the past.
Obesity can be a challenge for the DEXA equipment. First, the extra size can block the photons as they pass through the body and affect the score. Second, some manufacturers limit the size of the people who can take the test. One manufacturer has a weight restriction of 350 pounds.
It can be a challenge to get consistent bone mineral density scores for people who are thin. A Densitometry Technologist indicated to me that they can get three different scores when they take a DEXA scan of a thin person.
A thin person likely has porous bones and this can cause the distribution pattern of the photons to vary each time the scan is executed.
Skills and Qualifications of the Technologist
A technologist who is capable and careful will yield more accurate and dependable DEXA scan results compared to a poorly trained technician. Make sure your Technologist is accredited through a recognized body.
Quality and Maintenance of the DEXA Machine
DEXA technology is quite complex and the quality of machines can vary. DEXA experts we have spoken with recommend machines from GE Prodigy and Norland.
Another important factor that influences the measurement of the machine is the frequency and maintenance of the equipment. One of the leading medical imaging institutions I spoke to in Ontario indicated that they calibrate and test their DEXA machines every working day for accuracy.
In addition, they indicated that while their DEXA machines were 10 years old, they replaced the primary components every 3 to 5 years. These upgrades and replacements have improved accuracy and reduced radiation levels in their DEXA machines. The components that they change out include the tube, filter, target and the generator.
When Should You Have a DEXA Scan?
In many jurisdictions, including the United States and Canada, women over the age of 65 and men over the age of 70 are encouraged to have a DEXA scan for preventative screening purposes.
After the initial DEXA scan, individuals in this group are encouraged to have an examination every twenty four months.
In the United States, Medicare will cover the cost of a DEXA scan for women 65 or older and men who are 70 and older.
If you are a woman under the age of 65, you should consider a DEXA scan if the following applies to you:
- Family history of osteoporosis and, in particular, hip or vertebral compression fractures in your mother or father.
- Long term use of glucocorticosteroids, prednisone or other steroid-type drugs.
- Diagnosed with primary hyperparathyroidism.
- You smoke cigarettes.
- Menopause before the age of 40.
- History of a low impact fracture.
- Radiation therapy or chemotherapy for breast cancer.
It is a good idea to have a baseline DEXA scan as you enter menopause. The results of this examination will give you an accurate record of the change of your bone density as you progress through menopause. It can also motivate you to maintain (or even improve) your bone density through exercise and nutrition, thereby reducing the chance that you will have take a pharmaceutical like Prolia, Fosamax or Forteo later in life.
Once you have the baseline DEXA, there is no need to have another test for a number of years unless the baseline test identifies that you have low bone mass.
A baseline DEXA scan is appropriate for most men. Osteoporosis is not a woman’s only condition and men should not be dismissive of it. Bone density can decline at a more rapid rate during andropause when compared to menopause.
Baseline DEXA Score for Richard
After reading this post in June of 2019, my husband Richard, asked his physician to prescribe a baseline DEXA to measure his bone mineral density. Richard is in his late 50’s and younger than the typical age when males get a DEXA scan. Fortunately, Richard has an enlightened physician who supports the DEXA test for men and encouraged him to establish his baseline score.
Several weeks after receiving the prescription, Richard visited an imaging centre in Ottawa and completed the test. The intake process and procedure was similar to that described in this post. When he was setting up the appointment, the organizer made it clear that he should not take calcium supplements before the test and should wear clothing that did not have metal.
When Richard arrived for the procedure he had to complete a short intake form. It asked him if he had a history of fractures, took steroids in the past, and other relevant questions.
The intake form was handed to the Radiology Technologist. When she reviewed his form, she was surprised that he was taking the test at this time. He had no history of fracture and, according to guidelines she followed, he was too young to take the test. When Richard pointed out that he wanted a baseline score and that his mother and sister had osteoporosis, the Technologist was dismissive.
She begrudgingly administered the test and followed the procedures described in this post and Richard got what he wanted — a baseline score.
It is good to monitor your health and a baseline DEXA score is a step in that direction. Unfortunately, you might meet some resistance but I encourage you to press forward and manage your bone health proactively.
Room for Improvement
A study published in March, 2019 in The Spine Journal, Rates of osteoporosis screening and treatment following vertebral fracture, showed that, in some jurisdictions, that not enough people are getting DEXA scans.
Between 2008 and 2014, 2,933 unique patients visited emergency department for one or more vertebral fractures. The patients were 50 years and older. Of the patients that visited the emergency department, “ninety-eight percent did not receive a DEXA scan within the preceding 2 years or 1 year following fracture.” (5)
According to one of the co-authors, Jonathan J. Carmouche, M.D., Section Chief of Spine and Pediatrics for the Department of Orthopaedic Surgery at Carilion Clinic in Roanoke, Virginia, “We found that we, as the region’s premier tertiary care center, were dropping the ball on over 90% of vertebral fracture patients. They weren’t getting DEXA [bone density] scans to formally screen them for osteoporosis or diagnosed clinically and were therefore not being treated or were being under treated significantly.” (6)
Some of these patients probably fell through the cracks because they were under the age of 65, some might have been overlooked because their health care plans did not provide adequate screening coverage. However, it seems as though we should be more aggressive with this screening in order to get in front of vertebral and hip fractures.
How Much Radiation is in a DEXA Scan?
The DEXA scan examination is very safe. DEXA machine have been reducing the amount of radiation exposure to the point where radiation exposure from a DEXA machine is 1/100 or less compared with a lateral view X-ray of the spine.
Additionally, a Vertebral Fracture Assessment (VFA) can be done at the same time and location as measurement of BMD by DEXA.
How Often Should You Have a DEXA Scan?
How often you get a DEXA scan depends on a number of variables including your age and changes in health. The recommendations can vary across jurisdictions.
As I mentioned earlier, Medicare will provide a DEXA scan every twenty four months for women after the age of 65.
What are the Limitations of a DEXA?
The DEXA has several limitations:
- A DEXA scan is not able to tell you if you will have a fracture. It can only provide you with a measurement that gets interpreted into your relative risk for a fracture.
- The DEXA cannot tell you about your bone quality. If there is a feature to measure TBS, it can provide some insight into your lumbar spine.
- Spinal measurements are limited in individuals with spinal deformities such as scoliosis, moderate to severe osteoarthritis, pre-existing compression fractures, or spinal surgeries. (7)
What is TBS (Trabecular Bone Score)?
In the past two years I have noticed more information being provided in DEXA reports. One of the more common new features is something referred to as TBS. TBS is an abbreviation for Trabecular Bone Score.
As mentioned in past articles, bone density is only part of the equation that relates to bone strength. The other part is the quality of the bone. When it comes to research studies, bone quality is assessed with tools such as a QCT, Quantitative Computer Tomography. Due to the high levels of radiation exposure, the few number of machines available, and the cost of the examination, few individuals outside of research studies will ever be referred for a QCT.
The makers of DEXA machines have attempted to provide physicians with more insight into the quality of the bone through a measurement they call TBS. The TBS score is derived from the grey-level texture measurement of the lumbar spine DEXA.
A high TBS score indicates a stronger “internal scaffolding of the vertebra” — more trabecular that are closer together. Whereas a low TBS score indicates the opposite, more trabecular separation, fewer trabecula and therefore a higher risk of vertebral (spinal) compression fracture.
The following are some important guidelines for your DEXA bone scan preparation. Read these to prepare for a DEXA scan procedure.
- You should delay the DEXA scan if you are pregnant or if there is a possibility of you becoming pregnant. Should you decide to have the examination anyway, notify the medical professional performing the test.
- If you are scheduled to take an imaging examination that requires you to receive a dye or other contrast media either by intravenous (IV) injection or orally or rectally, the Central BMD examination should be performed prior to or at least seven days after such an imaging examination; e.g.: nuclear scan, CT scan, MRI, Barium studies etc.
On the day of your scheduled Central DEXA BMD (bone density test) examination and as part of your bone density test preparation, you should follow these patient preparation guidelines:
- Bring the Central DEXA BMD (bone density test) examination request your physician has provided along with your health insurance card to the examination facility.
- Show up 15 to 20 minutes prior to your appointment. This will give you ample time to register. Exams are usually booked back-to-back. Hence, punctuality is appreciated.
- Eat a normal diet on the day of the test.
- Take your medications as you normally would.
- Bring an up-to-date list of the medications you are taking.
- Leave any valuables or jewelry you normally wear at home.
Bone Density Test Preparation Calcium Intake
DO NOT take calcium supplements for at least 24 hours before the test.
Can You Eat Before a DEXA Scan?
You can eat your regular meals the day of the DEXA scan examination, however, you should not take calcium supplements at least 24 hours in advance of the scan.
Do You Have to Undress for a Bone Density Test?
In most cases you will not have to undress for a bone density test. The staff and clinician will make every effort to keep you in your own clothes during the examination. However, the staff may ask you to wear a gown.
Depending on the test center, the staff might request that you remove items that interfere with the DEXA scan including:
- Metal buttons
- Removable dental appliances
- Eye glasses
What to Wear for Bone Density Test
Here are guidelines on what to wear for bone density test, as well as what not to wear:
- Wear loose fitting clothes and avoid wearing accessories such as belts, clasps, hooks, zippers, thick buttons or glitter ornamentation.
- Note that bra hooks and metal buttons on back pockets may be unnoticeable to the eye but will interfere with the measurement procedure.
- Try not to wear body-piercing ornamentation to the examination.
What Should You Do if Your DEXA Indicates Your Bone Density Declines?
Patients often visit me because of a decline in their DEXA score. The reasons for the decline vary from individual to individual. The reasons for the change in scores include their unique genetic makeup, lifestyle, exercise habits, diet and medical history.
Response to DEXA Score Decline
The appropriate response to the decline can vary, as well. You should always discuss the right strategy with your physician. Your response can include a combination of changes to your:
- Exercise program.
- Activity level.
- Movement patterns (for example, how you lift things).
- Lifestyle activities (for example, if you are a gardener, consider hiring younger people to do the heavy activity around the garden.)
Depending on the degree of change, pharmaceutical intervention may be required to reduce fracture risk.
Factors to Consider After a DEXA Score Decline
Here are several factors to consider when you see a change in your DEXA scan scores:
- Is the bone density decline significant — to the point where your risk of a fracture is elevated?
- Are you able to make the lifestyle modifications required to improve bone density and reduce fracture risk?
- Were there life issues during the past few years which caused you to spend less time on your own health? Perhaps an aging parent or a sick family member took all of your energy and attention.
The correct response to the DEXA score decline for you depends on your medical history and the risk of fracture. It is important that you consult with qualified health professionals who can help you make the right decision for you.
Susan’s DEXA Story
Susan (not her real name) called me after a recent move from Virginia to Utah because she was concerned about the decline in her DEXA scan test results. Her DEXA scans were only taken 14 months apart.
With she moved across the country, she changed health care providers and doctors. Her new doctor requested a fresh DEXA test.
When I met with Susan she mentioned her surprise in the loss of BMD in just over a year. Before discussing her exercise regime and how she could better address bone loss, I took a look at her BMD DEXA scores.
Different manufactures produce very different DEXA machines. Their results should not be be compared. Even machines produced from the same company will not be perfectly identical.
When I read that Susan had moved across the country, I requested all of her DEXA results to ensure that the appropriate intensity of exercise was prescribed. Both locations used machines from the same manufacturer, which made me more comfortable to put some weight in comparing results.
My Interpretation of Susan’s DEXA
After looking at the different DEXA scan results, here is what I found.
DEXA Hip Scores
It seemed like Susan had hit the perfect storm of DEXA inconsistencies.
Many reports only provide the BMD of one hip. This was the case for her first DEXA scan in Virginia where they only had a reading for her left hip. In Utah, she had a BMD of both hips but the report only reported on the right. Her right hip BMD was significantly lower than the left hip BMD. However, when you compared the BMD of her left hip from year to year it was unchanged.
DEXA Spinal Scores
DEXA measurements of the spine are usually taken of the top four lumbar vertebra, L1, L2, L3, L4. The scores of all each vertebra was recorded in both locations. In the east coast, they took the average of all four L1 – L4 measurements. In Utah, they only took the average of her top two vertebra, L1 and L2, they had the weakest scores.
By only using the average of her two weakest scores and not averaging the reading over all four vertebra, it appeared that she had lost significantly more bone.
DEXA and the Upper Thoracic Area
Some of the newer DEXA centres have apps that allow them to get views of the spine from the upper thoracic area (just bellow the shoulders) to the low back. Fortunately, Susan sent me the entire report. Well into the report there was a very noticeable Stage 2 compression fracture.
The radiologist had noted it but her physician had failed to tell her about it. When I asked her if she had a past episode of back pain or a fall she did recall a severe episode shortly after her move. In fact she did not have a fall. During the move she unpacked a lot of boxes and helped her husband with yard work. The pain lasted 6 to 8 weeks. Because she had relief with Physical Therapy, she forgot to mention it in her intake.
From my point of view her vertebral compression was a game changer. We now had information on the quality of her bone.
Lesson Learned from Susan’s Story
There are several important lessons you can take from Susan’s experience.
1. DEXA Scan Comparison for Femoral Neck
When comparing DEXA reports be sure you compare apples to apples. Right hip to right or left hip to left.
Several studies have looked at the differences between BMD of the right and left femoral neck (hip) in postmenopausal women. The 2012 study of 384 postmenopausal Korean women showed a discordance rate of about 30%. (10)
A 2017 study with 133 individuals showed an inconsistency in 44% of the cases when they were classified by T or Z-scores, with the lowest scores found in the dominant leg. (11) While discussing similar results with researchers at a bone research conference a few years back, we hypothesized that since we lead with the dominant leg the non-dominant leg gets more of the weight bearing such as when kicking a ball.
2. DEXA Scan Interpretation for the Spine Results
When comparing DEXA’s of the spine, they should look alike. Check the size and appearance of the boxes. Also be sure that they are comparing the same parts of the spine L1 to L1, L2 to L2, and so on or as in Susan’s case that they are taking the average of the same vertebra.
3. DEXA Scan and the Thoracic Spine
Another word of caution in regard to DEXA’s and your spine. If the medical imaging institution that you have your DEXA done does not have an app that looks at a bigger picture of your spine then you have to be your own advocate.
The most common fracture sites in the osteoporotic spine is in the thoracic spine, just around your bra strap. For men, this is just below the bottom of your shoulder blades. DEXA reports never capture the thoracic spine for BMD recording because of the interference of our ribs and breast bone.
However, if you have height loss or you have had sudden onset of back pain that persisted for over 4 weeks then the possible source could be a compression fracture of your vertebra.
Robert Hakim generously contributed to this article. He wrote the section dedicated to how to prepare for your DEXA exam. Robert M. Hakim M.R.T. (R.), RTR, CDT is a Clinical Densitometry Technologist atDiagnostic Imaging Department – Georgetown Hospital, Halton Healthcare Services Corporation, Halton Hills, Ontario. Robert is a Member of the International Society of Clinical Densitometry.
Primary Reference Material
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- Over 90% of Fracture Patients do not get a Density Scan! Orthopaedics This week. February 28, 2019.
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- Afzelius P, et al. Dual-energy X-ray Absorptiometry of Both Hips Helps Appropriate Diagnosis of Low Bone Mineral Density and Osteoporosis. Diagnostics. 2017 Jul 9;7(3). pii: E41. doi: 10.3390/diagnostics7030041.
Secondary Reference Material
- Siminoski K, “Tools and Techniques”, Osteoporosis Update, Spring/Summer 2005, Volume 2.
- Winzenrieth R, Michelet F, Hans D. Three-dimensional (3D) microarchitecture correlations with 2D projection image gray-level variations assessed by trabecular bone score using high-resolution computed tomographic acquisitions: effects of resolution and noise. J Clin Densitom. 2013 Jul-Sep; 16(3):287-296.
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- Yong Jun Choi. Dual-Energy X-Ray Absorptiometry: Beyond Bone Mineral Density Determination. Endocrinological Metabolism. 2016 Mar; 31(1): 25–30.
- Han J, Hahn MH. Proximal Femoral Geometry as Fracture Risk Factor in Female Patients with Osteoporotic Hip Fracture. Journal Bone Metabolism. 2016 Aug;23(3):175-82. doi: 10.11005/jbm.2016.23.3.175. Epub 2016 Aug 31.
For more information, check out my Osteoporosis Guidelines.