As we age, the spine undergoes various degenerative changes due to the natural wear and tear of its structures, including intervertebral discs, vertebrae, ligaments, and facet joints. These changes can lead to conditions such as spinal stiffness, reduced flexibility, and sometimes pain or discomfort. Lumbar spine DXA scans are essential in detecting these age-related changes, helping healthcare professionals assess bone density and identify potential risks for osteoporosis or fractures.

Understanding Age-Related Changes in the Spine

One of the earliest changes occurs in the intervertebral discs, which act as cushions between the vertebrae. Primarily composed of water, these discs lose moisture and elasticity over time, becoming thinner and less effective at absorbing shocks. This degeneration can lead to a reduction in disc height, contributing to a shorter stature and increased pressure on surrounding spinal structures.

The facet joints, which provide stability and allow for controlled spinal movements, often develop osteoarthritis due to cartilage breakdown. This can result in bone spurs (osteophytes) that may irritate or compress nearby nerves, potentially leading to conditions like spinal stenosis or sciatica.

Additionally, the ligaments supporting the spine may thicken and lose their flexibility, further contributing to spinal stiffness. The vertebrae themselves can undergo changes, such as decreased bone density, making them more prone to fractures (vertebral compression fractures) in older individuals, especially those with osteoporosis.

Impact of Degenerative Changes on Lumbar Spine DXA Scans

Degenerative changes in the lumbar spine (L-spine) can significantly affect bone density measurements obtained through dual-energy X-ray absorptiometry (DXA) scans. These changes, including osteophyte formation, facet joint osteoarthritis, and vertebral fractures, often lead to artificially elevated bone mineral density (BMD) readings, potentially masking true osteoporosis or osteopenia.

Osteophytes, or bone spurs, are common with spinal degeneration and contribute additional bone mass that DXA scans may incorrectly interpret as increased BMD. This can lead to falsely high T-scores and a misclassification of a patient’s bone health status. Similarly, calcification of soft tissues or thickened ligaments, such as the ligamentum flavum, can further distort scan results.

Degenerative joint disease in the lumbar spine often causes variability between different vertebrae. Some vertebrae may show elevated BMD due to these changes, while others may not, leading to inconsistencies in DXA scan interpretations. Vertebral compression fractures, often linked to both aging and osteoporosis, can also affect measurements by altering the structure of the vertebrae and concentrating bone density in smaller areas.

Best Practices for Accurate DXA Scan Interpretation

Technologists need to carefully analyze L-spine DXA scans with the presence of degenerative changes. Excluding individual vertebrae that are affected by spinal pathology may be necessary to get a true result.  However, it must also be recognized, to get diagnostic results for a l-spine DXA scan that you must have at least 2 diagnostic vertebrae. Otherwise, you may have to supplement the lumbar spine scans with a forearm DXA assessments, which is less affected by degenerative changes.  Correlating findings with forearm clinical assessments can help provide a more accurate evaluation of a patient’s bone health if the Lumbar spine is unavailable for diagnosis.

When to Exclude Vertebrae from DXA Analysis

When performing a DXA Scan, you may find that excluding certain vertebrae is necessary  to ensure an accurate BMD assessment and avoid misinterpretation due to structural abnormalities or artifacts. The primary reasons for exclusion include:

• Degenerative Changes – One primary reason for exclusion is the presence of degenerative changes, such as osteophytes (bone spurs), facet joint osteoarthritis, or vertebral compression fractures. These changes can artificially elevate BMD readings, leading to falsely high T-scores that do not accurately reflect the patient’s true bone health status.
  
  
• Structural Anomalies – In some cases, technologists may need to exclude the lumbar spine entirely from DXA analysis. This is necessary when the scan is non-diagnostic due to significant factors such as severe scoliosis, advanced degeneration, compression fractures, or artifacts like surgical rods and screws.
  
  
• Inconsistent BMD Values – Vertebrae may also be excluded if they exhibit significant anomalies or structural irregularities, such as scoliosis or surgical implants, which can distort the scan results. Inconsistent BMD values across adjacent vertebrae, such as a sudden increase or decrease of over 1.0 standard deviation, may indicate an artifact or degenerative condition, prompting exclusion.

For a clinically meaningful assessment, only unaffected and reliable segments should be analyzed. If all four lumbar vertebrae are compromised, scanning the forearm becomes necessary. Additionally, if there is a significant discrepancy between hip and spine T-scores (exceeding one standard deviation), a forearm scan should be performed for a more comprehensive evaluation.

Conclusion

By excluding affected vertebrae and analyzing only unaffected, reliable segments (typically requiring at least two contiguous vertebrae), clinicians can obtain a more accurate and clinically meaningful assessment of BMD. This careful approach helps in diagnosing osteoporosis, evaluating fracture risk, and guiding appropriate treatment decisions.

It is important to remember that DXA scanning can be extraordinarily complex. Thankfully, Advanced Health Education Center has a great bone density two-day initial training course you can sign up for today.