Which lumbar vertebra is characterized by an X or H shape on a DXA PA spine scan?

• A. L2
• B. L3
• C. L4
• D. L5

Answer: (C)

The lumbar vertebra characterized by an X or H shape on a DXA PA spine scan is L4. This shape is notable due to the unique anatomical features of L4 compared to the other lumbar vertebrae. On DXA scans, L4 often presents this distinct bifid appearance because of the orientation and shape of its spinous process and transverse processes, which are less pronounced than those in the adjacent lumbar vertebrae.

Identifying the shape on a DXA scan can assist healthcare professionals in recognizing and assessing bone health, particularly when tracking conditions such as osteoporosis. The specific morphology of L4 is crucial in ensuring accurate measurements and avoiding misinterpretation, which could lead to misdiagnosis or inappropriate management of bone health in patients. Understanding these anatomical differences helps in both imaging interpretation and the overall context of bone densitometry assessments.