Trabecular Bone Score and the Quest to Predict Who Will Fracture

Each year 178 million new osteoporotic fractures occur worldwide. These fractures are painful, costly, and at times life-limiting. In the hope of preventing these fractures, medical systems around the world have looked for ways to identify those at greatest fracture risk. In Traditional Chinese Medicine the kidney energy meridian system is evaluated, as this is held to largely dictate bone health. In the 5,000-year-old Ayurveda Health Science of India those with an imbalance of the Air and Ether elements (known as Vata dosha) carry an increased fracture risk.

Westernized countries have taken the route of X-ray technology to both predict who will fracture and define osteoporosis. You may have heard of the Trabecular Bone Score (TBS), the “new kid on the block” of X-ray fracture risk assessment. Let’s begin by putting TBS in its proper historical context.

The U.S. Fracture Prediction Quest Timeline: Where TBS Fits In

• 1985, Harvard University, firsthand account, as I was there

In 1985, a small group of bone researchers met at Harvard University to announce their groundbreaking development of advanced X-ray technology that could measure bone density. I attended this meeting and sensed an air of excitement and optimism as we were told that science would now be able to predict who would fracture using this bone density measurement machine. This was the birth of the DEXA bone density device still being used today.

• 1985 to 1994

These new bone density testing machines were put into service and hundreds of thousands of women, and selected men, received bone density testing. Data from these 10 years were analyzed over time.

• 1994, Geneva, Switzerland

A handful of doctors met in Geneva, Switzerland in 1994 under the auspices of the World Health Organization. Using the 10 years of bone density testing data, they developed both a new definition of osteoporosis, and a new way to predict fracture. By their action osteoporosis was now to be defined by bone density T-Scores. As a result of these decisions, you are now told you have “osteoporosis” if your T-score is -2.5 or higher.

As data on the correlation between bone density T-score and fracture risk were analyzed over the next 20 years, the inability of bone density testing to predict fracture was becoming obvious.

• 2008, UK

Researchers introduced the FRAX (Facture Risk Assessment Tool) as an adjunct to the bone density testing to improve fracture prediction. The FRAX questionnaire consists of 11 known clinical risk factors for osteoporosis (age, sex, weight, height, previous fracture, parent fractured hip, current smoking, glucocorticoids steroid medications, rheumatoid arthritis, known secondary osteoporosis, and alcohol intake).

The hope was that the addition of this FRAX questionnaire would enhance the fracture predictability of the DEXA bone density results. Success was limited as there are more than 100 risk factors for osteoporosis.

• 2014 and beyond

Extensive analysis of the correlation between bone density scores and fracture incidence revealed that the likelihood of fracture could not be predicted effectively through DEXA bone density. Up to 80% of all osteoporotic fractures were shown to occur in those who did not have an osteoporotic T-score of -2.5 or greater. Further, many of those with an osteoporotic T-score did not fracture.

• 2015, The Trabecular Bone Score

In 2015 the International Society for Clinical Densitometry published its first official position on the Trabecular Bone Score (TBS). The TBS then became used as an adjunct to DEXA bone density testing. Again, the hope was to improve the fracture prediction capacity of DEXA bone density testing.

Trabecular Bone Score (TBS): What It Is

At the Center for Better Bones, we see the trabecular bone score as an interesting attempt to rectify some of the shortcomings of DEXA bone mineral density. Specifically, DEXA bone density testing does not reveal real bone strength, and bone strength is most likely what predicts fracture.

The TBS is a parameter that attempts to capture bone strength by assessing the microarchitecture of lumbar (lower spine) trabecular bone (internal spongy bone). This is done by amplification and analysis of the radiographic image from the bone density testing machine. The goal is to discern differences on 3-dimensional microarchitecture between 2- dimensional DEXA measurements that present with similar bone mineral density.

To date several researchers have suggested that a higher TBS value is associated with a better and more fracture-resistant bone microarchitecture. A lower TBS value, they report, is associated with weaker, more fracture-prone bone microarchitecture.

Determining who will fracture, however, is a complicated endeavor and not all research on TBS supports its value for fracture prediction. For example, one study suggested a significant TBS fracture predictive value for Caucasian American women, but not for African Americans or Mexican Americans. Overall, it will take many more years of study to reveal the true fracture predictive value of the TBS.

Nonetheless, at the Center for Better Bones we feel that for some the TBS might be a worthwhile adjunct to the current DEXA bone density test. However, this test is not widely available. Currently few DEXA bone testing devices have the software necessary to produce the Trabecular Bone Score and it may be difficult to find one in your area.

To find a bone testing device that can also give you a TBS  score, you can ask at the office where you get your DEXA test. We have been lucky enough to find a quality technician at Body Analytics in St. Louis, MO.  Watch this short video with Dr. Brown and our colleague Johnny Harper from Body Analytics to learn more about why this test might benefit you and why you should seek out an experienced technician!

References

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Jain, R. K. and T. Vokes. 2018. Association of trabecular bone score (TBS) and prior fracture differs among minorities in NHANES 2005-2008. Osteoporosis International 29(9):2093-2099.

Järvinen, T. L. N., et al. 2015. Overdiagnosis of bone fragility in the quest to prevent hip fracture. BMJ 350:h2088.

Lekamwasam, S., et al. 2020. Ability of FRAX Sri Lanka adjusted for trabecular bone score to discriminate between postmenopausal women with a recent fracture and without a fracture. Osteoporosis and Sarcopenia 6(3):106-110.

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