Which lumbar vertebra is the largest of the vertebrae typically measured for DXA?

• A. L1
• B. L2
• C. L3
• D. L4

Answer: (C)

The lumbar vertebra typically measured for Dual-energy X-ray Absorptiometry (DXA) is the third lumbar vertebra, known as L3. This vertebra is significant because it is generally the largest of the lumbar vertebrae, providing a reliable site for assessing bone mineral density (BMD). The choice of L3 for measurement in DXA is due to its location and anatomical characteristics, which allow for better standardization and comparison across different populations.

L3 is also a critical site because it tends to show changes in bone density related to conditions such as osteoporosis. Measuring at this specific vertebra helps in diagnosing changes in bone health and in managing treatment plans. The findings from L3 can be influential in assessing overall skeletal health, making it an essential focus in bone density evaluations.

Understanding the reasons behind focusing on this vertebra can help gauge the effectiveness of interventions and monitor the progression of bone loss over time, making L3 a key component in the DXA measurement framework.