Which vertebra is characterized by an "H" or "X" shape on a DXA scan?

• A. L1
• B. L3
• C. L4
• D. L5

Answer: (C)

The vertebra characterized by an "H" or "X" shape on a DXA scan is typically L3. This shape is indicative of the trabecular pattern within the vertebra and can help radiologists and clinicians identify and assess bone density in the lumbar spine. The "H" or "X" shape arises from the arrangement of the vertebral trabecular bone, which can be particularly relevant for detecting osteoporosis or other conditions affecting bone density. L3 is often evaluated due to its mid-lumbar position, providing a representative assessment of overall lumbar bone health. The distinct appearance can signal variations in bone density which are crucial for diagnosis and monitoring purposes in bone densitometry.