Assessing bone health is an important part of preventative medicine, particularly as individuals age. The strength of our bones determines their resilience against fractures, which can significantly impact quality of life. Understanding the tools available for evaluating bone health is the first step toward proactive management and making informed health decisions.
Understanding the DEXA Scan
The primary tool for evaluating bone health is the Dual-Energy X-ray Absorptiometry (DEXA) scan. This procedure is the established standard for measuring bone mineral density (BMD), which is the amount of mineralized tissue in a specific volume of bone. The scan is a non-invasive process, taking about 10 minutes and using low-dose X-rays to examine areas prone to fracture, most often the hip and lower spine.
DEXA scan results are reported using a T-score, which compares your BMD to that of a healthy young adult. A T-score of -1.0 or above is considered normal. A score between -1.0 and -2.5 indicates osteopenia, or lower-than-normal bone mass, while a T-score of -2.5 or below leads to a diagnosis of osteoporosis.
The T-score provides a standardized metric for clinicians to diagnose bone loss and estimate fracture risk. This measurement is the benchmark for discussing lifestyle changes, supplements, or medical treatments to protect the bones.
Defining the Trabecular Bone Score
While a DEXA scan measures bone quantity, the Trabecular Bone Score (TBS) provides insight into its quality. TBS is not a separate scan but an advanced software analysis applied to lumbar spine images captured during a standard DEXA procedure. This analysis can be performed without additional time or radiation exposure, as the software assesses the gray-level texture of the DEXA image to evaluate the underlying bone microarchitecture.
This microarchitecture is the internal, honeycomb-like structure of trabecular bone. A strong, well-connected network provides significant resilience. For example, imagine two bridges built with the same amount of steel. One has a robust, interconnected internal lattice, while the other has a weaker structure. Though their material quantity is identical, the bridge with the superior internal design is far stronger.
TBS evaluates this internal bone structure. A high TBS value suggests a healthy, strong trabecular network, while a low score indicates a degraded, more fragile microarchitecture. This information is a direct reflection of bone quality, offering a perspective on bone strength beyond density measurements.
The Complementary Relationship
These assessments are most powerful when used together. Bone mineral density from a DEXA scan does not provide a complete picture of fracture risk, as people with similar bone density can have different risks due to bone quality. Relying on BMD alone can miss up to half of the individuals who will experience a fracture.
TBS adds a qualitative dimension to the DEXA scan’s quantitative data, providing a more refined fracture risk prediction. For example, a person with a normal or osteopenic T-score might still have an elevated fracture risk. If their TBS score is low, it indicates poor bone microarchitecture, increasing their actual risk beyond what BMD alone suggests.
Conversely, a patient with osteopenia might have a high TBS, suggesting that the quality of their bone is good despite lower mass, potentially lowering their fracture risk. By combining BMD with TBS, clinicians can create a more comprehensive and personalized risk profile. This dual approach improves the identification of patients at high risk for an osteoporotic fracture.
Clinical Application and Patient Considerations
A Trabecular Bone Score is valuable in specific clinical scenarios. A TBS analysis is helpful for patients whose fracture risk seems inconsistent with their BMD, such as those who fracture despite a normal T-score. It is also useful for assessing patients with conditions that degrade bone microarchitecture, like type 2 diabetes, kidney disease, or those on long-term steroid therapies.
For these individuals, a DEXA scan might not fully capture their risk, but a TBS analysis can reveal underlying structural weaknesses. The software required for TBS is not installed on every DEXA machine, so its availability can vary by imaging center and location.
Patients concerned about bone health, especially those with risk factors for osteoporosis or a history of unexplained fractures, should discuss this technology with their doctor. Asking if a TBS analysis would be beneficial is a proactive step. This can help determine if a more detailed assessment is needed to guide preventative care.