Osteoporosis: Do You Know Your Risk of Fragility Fractures?

About two weeks, after I fractured my shoulder a few years ago, I got a phone call from Kaiser Permanente, the health system where I get my care. The woman on the line identified herself as being part of my medical center’s Bone Health team. She said they were calling me because I had sustained a fracture that is suggestive of low bone density. She called it a fragility fracture.

What are fragility fractures?

Fragility fractures are fractures that occur as a result of low energy trauma, for example, falling from a standing height – or no trauma at all [1].

Common fragility fractures include the following:

• • • vertebral fractures,
    • humeral head (shoulder) fractures,
    • fractures of the neck of the femur (a.k.a. hip fractures), and
    • Colles fractures of the wrist.

It turned out that Kaiser routinely scans its electronic health records in order to identify patients with these types of fractures so they can bring them in to evaluate their bone health.

How a population health program can help identify “silent” osteoporosis

My first reaction to hearing that I had a fragility fracture was “I am not fragile, I just tripped and fell.” But the Bone Health lady pointed out that people with normal bone health don’t usually fracture their big bones (humerus or femur) when they fall from a standing height. She said I needed to come in for a bone density test and blood tests to measure my vitamin D level (amongst other tests) to determine my risk of fragility fractures.

I was impressed. I am a long time fan of population health programs [2] and have seen health plans and provider groups use them to proactively reach out to people with diabetes, heart failure, and asthma.

At the time, I had never come across a population health program that targeted osteoporosis even though, according to the National Osteoporosis Foundation, 54 million Americans have either osteoporosis or low bone density (osteopenia).[3] Not only that, but 1 in 2 women and 1 in 4 men over the age of 50 will break a bone due to osteoporosis.

Think about that for a minute! That’s an awful lot of people who will experience the pain, suffering, and cost of a bone fracture that perhaps could have been prevented if their low bone density had been detected earlier.

Routine screening for osteoporosis

Hopefully, you won’t wait until you sustain a fragility fracture before being evaluated for your risk of sustaining one. In fact, the USPSTF, a respected organization that reviews guidelines for the prevention of health conditions has concluded with moderate certainty that there is “at least moderate benefit” of screening for osteoporosis in the following individuals [4]:

• women 65 and older 
• postmenopausal women younger than 65 years who are at increased risk of osteoporosis is at least moderate

However, they found that current evidence is “insufficient to assess the balance of benefit and harms of screening for osteoporosis in men.” This was primarily based on the lack of evidence for effective treatments of osteoporosis in men.

The USPSTF report states that,

“…it cannot be assumed that [effective treatments for women] will be equally effective in men because the underlying biology of bones may differ in men due to differences in testosterone and estrogen levels.”

Bone mineral density (BMD) tests

 Bone density tests—also called Bone Mineral Density (BMD), DXA, or DEXA (for dual-energy X-ray absorptiometry) test are very important in making the diagnosis of low bone density (osteopenia or osteoporosis).[5]

In addition, they are used to predicting the risk of fractures, particularly when used in conjunction with a bone fracture risk prediction tool, such as the Fracture risk assessment (FRAX) tool (see below). Finally, BMD tests are also used to assess changes in bone density over time and to monitor the effects of treatment.

The BMD machine works by firing X-rays from two different sources through the bones that are being tested towards a detector. The use of two different X-ray sources rather than one allows a more accurate reading of bone density. Mineralized bone blocks a certain amount of the X-rays. The denser the bone is, the fewer X-rays get through to the detector.

There is no special preparation required for the test, although you should let your physician know ahead of time if there is a possibility you are pregnant or if you recently had a barium exam or received an injection of contrast material for a CT or radioisotope scan. Some also recommend that you refrain from taking calcium supplements for 24 hours before the test as they could interfere with the images.[6].

You will be asked to remove any jewelry and change into a hospital gown. Then, you will be positioned on your back on a special examination table. For part of my exam, I had a rectangular-shaped foam pillow placed under my knees and I was asked to remain very still while the machine was actively scanning the bones of my back (the vertebrae) and hip.

If you are unable to lie down so that the spine and hip can be imaged (these provide the best images to predict the risk of osteoporotic fracture) you may instead have a DXA scan of your forearm to establish the diagnosis of osteoporosis.

The total time for the test—scan time plus repositioning time—is about 10 to 15 minutes, depending on which parts of your body are being examined. I was walking back to my car 20 minutes after I checked in for the test—and that included stopping at the lab for some blood tests.

Be sure your doctor is sent the images as well as the summary test results for the best understanding of the findings.

By the way, is important to know that a BMD test is not the same thing as a bone scan that may be used to look for other types of abnormalities in your bones, such as metastases from cancer, infection, or inflammation.

The FRAX tool

At some time before you get your BMD test, you will likely be asked to fill out a FRAX Fracture Risk Assessment Tool.[7] It will look something like this. Information from this test is used to calculate your overall fracture risk as will be explained below.

Please click on the link to get more detailed instructions about how to fill out the form. (Screenshot of FRAX Questionnaire from https://www.sheffield.ac.uk/FRAX/tool.aspx?country=9) 

There are a number of other risk assessment tests available but the FRAX is the most commonly used at the present time.

Understanding the results

The data from the X-ray detector is sent to a computer which calculates a score of the average density of the bone in grams/cm². The computer program compares your score to groups of people of the same ethnicity and gender to calculate two different scores, a T-score and a Z score. When you get the results (and you should ask for a copy of the full report) it will look something like this:

“A bone mineral density (BMD) measurement was performed of the L1-L4 vertebrae and the proximal femur (total femur, neck, trochanteric, and intertrochanteric region) using a Hologic Dual Energy X-ray Absorptiometry Model Discovery C machine.”

• Have repeat tests done using the same make and model as prior tests

You will want to know the name and model of the machine as it is important in determining your fracture risk. It is also important for your clinician to know this information because the results may vary by the type of machine used. Comparing the results to a prior test done on a different make and model of machine can be problematic.

• Your values are compared to a reference population

The test result will also describe the measurement values and the comparison group:

“BMD values were determined in gms/cm² and compared to a young normal
reference population (T-score = standard deviations (SDs) below or above the young normal mean), and to an age-matched normal reference population
(Z-score = SDs below or above the age-matched normal mean).”

• The T and Z scores are both important

The T and Z scores are both important when interpreting the results and deciding if you need treatment. The T-score compares your bone density to that of young normal individuals. Bone density peaks somewhere between 18-35 years old. After that, there is a steady loss of bone that accelerates after menopause and doesn’t slow down again until the age of 70 or so. 

The T-score tells you how much bone you have lost compared to an average peak value of young healthy individuals of the same sex and ethnicity. The Z-score compares your bone density to that of people of the same gender and ethnicity and approximately your same age.

If this score is lower than the reference population, it suggests you are losing bone faster than the average for your peers. This alerts you and your doctor that something other than “normal” bone loss due to aging may be going on.

For example, excessive bone loss may be due to taking certain kinds of drugs, such as glucocorticoids, aromatase inhibitors, or certain types of anti-epilepsy drugs. This type of osteoporosis is referred to as secondary osteoporosis (secondary to a factor other than aging).

• Understanding caveats about the reference group

Information will be provided that will help you and your doctor understand some details about the comparison group. Mine test results included this statement:

“Reference BMD values for the hip were derived from the NHANES data and for the spine from the Hologic reference data. According to the WHO, criteria osteoporosis is defined by T-scores but you should note that these are only defined for a Caucasian female 65 years or older.”

• Best practices in BMD testing

According to an excellent review of best practices for Bone Mineral Density testing published in Volume 19 of the 2016 Journal of Clinical Densitometry (yes, there is such a journal)[8]:

“Manufacturers are advised to use National Health and Nutritional Examination Survey III young adult Caucasian female BM data as the reference standard for femoral neck and total proximal femur T-score calculation.”

They can use their own reference data for lumbar spine T-score calculation.

This review makes it clear that, as is true of most things in medicine, the devil is in the details. BMD tests need to be performed properly with well-trained technicians and properly calibrated and maintained machines. The interpretations must be done by people who know what they are doing and understand the critical importance of applying the correct comparisons.

Embarking on treatment for osteoporosis requires that best practices be followed.

“A normal T-score is between 0 and -1.0. Osteopenia is defined as a T-score of -1.1 to -2.4. Osteoporosis is defined as a T-score of less than -2.5.”

Assessment of risk of fragility fractures

The T-score is only one piece of information that is used to estimate the risk of having an osteoporotic fracture over the next 10 years. Although there are several fracture risk predictors available, the one most commonly used is the FRAX tool (shown above). You can find an online FRAX calculator here: www.shef.ac.uk/FRAX

The FRAX tool calculates risk based on age, gender, BMI, and the clinical risk factors reported obtained from a questionnaire filled out at the time of the bone density test (see above).

You can get an estimate of your risk even if you have not yet had your BMD test. But it is more accurate if you are able to include the measured density of your femoral neck—note that you will be asked to include the make of the machine used for your test.

The clinical risk factors considered by FRAX are:

• a previous fracture
• a parent who fractured a hip
• current smoking
• use of glucocorticoids
• rheumatoid arthritis
• a diagnosis of secondary osteoporosis
• alcohol intake greater than 3 units per day

This is how this information appeared in my report:

“10-year fracture risks were calculated using the World Health Organization FRAX tool based on the age, gender, BMI, clinical risk factors reported by the patient, and the BMD of the femoral neck measured. Clinical risk factors considered by FRAX are: previous fracture, parent fractured hip, current smoking, glucocorticoids, RA, 2nd osteoporosis, and 3 or more alcohol units per day.”

The FRAX score (estimated risk of having an osteoporotic fracture over the next 10 years) is reported as two different risks: The percent risk for any major osteoporotic fracture and the percent risk for a hip fracture.

Who should be considered for treatment?

My report also contained the following language about treatment:

“National Osteoporosis Foundation recommends to consider initiating therapy:

1) postmenopausal women and men age 50 and older with hip or
vertebral fractures, or fragility fractures
2) DEXA BMD T-scores -2.5 or below (after excluding secondary reasons for
osteoporosis)
3) For osteopenic patients: 10-year hip fracture probability < 3% or a 10-year major osteoporosis-related fracture probability < 20% based on the US-adapted WHO absolute fracture risk model FRAX…

…all treatment decisions require clinical judgments and consideration of clinical risk factors that may or may not have been captured in the FRAX model and possible under-or-over estimation of fracture risk by FRAX.”

Missing from the report, but very important is the patient’s preference. Failure to take this into account may be one reason why so many people refuse to initiate treatment, fail to take medications as prescribed, or discontinue treatment that could be beneficial. We will, of course, dive into all of the issues related to the treatment of osteoporosis in a future post.

Want to share your personal journey?

Meanwhile, please leave a comment or contact me at info@thedoctorweighsin.com if you would like to share your personal journey with osteoporosis. Please do not leave comments asking for medical advice as that is best discussed with your doctor.

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