Bone Microarchitecture: Why Two People With the Same DEXA Score Don’t Have the Same Fracture Risk - Dr Sanjib Kumar Behera

Bone mineral density (BMD) is often treated as the gold standard for gauging fracture risk. DEXA scans, widely used in clinics to detect low bone mass, provide a quick overview of mineral content. Yet, many patients with the same T-score do not share the same vulnerability to fractures.

This difference points to the fact that the scan doesn’t reveal the internal structure and quality of the bone itself.

More Than Just a Number

While BMD gives a measure of how much mineral is present, it doesn't reveal how that mineral is arranged. Two people with similar BMD may differ in how strong or resilient their bones are.

For example, trabecular bone, the spongy part found in the spine and ends of long bones, can appear fine on a scan, but may be riddled with microdamage or weakened architecture. This means bones can be fragile, even when the density reading appears acceptable.

There are real-life cases where a person with a T-score of –2.5 stays active without incident, while another with the same score suffers a fracture after a low-impact fall. Something more than mineral count is at play.

The Role of Trabecular Bone Quality

Imaging advancements are beginning to capture what BMD cannot. Tools like Trabecular Bone Score (TBS) assess the textural variation in standard DEXA images. A low TBS reading signals poor trabecular structure, thin, disconnected, or poorly organised bone, even if the BMD appears adequate.

Similarly, high-resolution peripheral scans (HR-pQCT) can detect early loss of bone structure, though they are mainly used in research settings for now. What they reveal is simple: it’s not just about how dense the bone is, but how well it’s built.

Why Muscle Health Matters

Fractures aren’t just a matter of weak bones. The muscles around the skeleton are just as important in keeping joints stable and movement secure. As people grow older or lead less active lives, muscle strength naturally diminishes, a process known as sarcopenia.

When this happens, the risk of falling increases, and the body becomes less capable of absorbing shocks that might otherwise be harmless.

Muscle and bone also work as a unit. The stress placed on bones by movement helps stimulate bone formation. So, reduced activity or poor muscle mass leads to lower mechanical stress, which in turn contributes to weaker bones.

Even with a decent BMD score, the absence of supportive muscle tissue makes a fracture more likely.

The Lifestyle and Medical Factors at Play

Nutrition, exercise, and chronic illness all affect bone quality. Inadequate intake of calcium, vitamin D, and protein reduces both bone and muscle strength. Systemic conditions like diabetes, thyroid imbalances, rheumatoid arthritis, or prolonged use of steroids quietly degrade bone over time.

Sedentary habits make the problem worse. Without consistent weight-bearing or resistance exercise, the internal structure of bone loses strength. Smoking and frequent alcohol use also interfere with bone repair and raise the risk of tiny fractures.

A Broader Way to Assess Risk

While DEXA scans remain useful, they must be supported by other tools. The FRAX tool, for instance, includes various inputs like age, BMI, previous fractures, and medication history to estimate the 10-year risk of major fractures. However, FRAX does not account for bone microarchitecture or muscle condition.

A more complete risk assessment includes:

• DEXA and TBS used together for better insight

• Muscle strength checks (like grip tests or gait analysis)

• Fall risk evaluation based on balance and mobility

• Nutritional and metabolic reviews

• Screening for chronic diseases that silently affect bones

This holistic view gives a more realistic idea of which patients are genuinely at high risk, even if their BMD seems borderline.

Fractures aren’t always about how dense the bone is. They’re often about how well the bone is built, how strong the supporting muscles are, and how the entire body is functioning. A narrow focus on DEXA scores alone may miss warning signs that are just as important.

Bone health must be understood as a mix of structure, strength, and function. With the growing availability of tools like TBS and broader assessment frameworks, orthopaedic care can move toward truly preventive treatment tailored not just to numbers, but to the real-world risks each patient carries.

Disclaimer: The views expressed in this article are of the author and not of Health Dialogues. The Editorial/Content team of Health Dialogues has not contributed to the writing/editing/packaging of this article.