What percentage of trabecular bone is found in the PA spine?

• A. 50%
• B. 66%
• C. 75%
• D. 80%

Answer: (B)

In the PA (posteroanterior) spine, it is generally accepted that approximately 66% of the bone present is trabecular bone. Trabecular bone, also known as cancellous or spongy bone, is the softer, porous type of bone found within the interior of bones, particularly in regions such as the spine, pelvis, and femur.

The significance of trabecular bone lies in its metabolic activity and its responsiveness to changes in mechanical loading and hormonal influences. The presence of a high percentage of trabecular bone in the spine is important in the context of bone density assessments, as it makes up a substantial portion of the material measured during bone densitometry.

Understanding that about two-thirds of the bone in the lumbar region is trabecular helps in interpreting bone density results and assessing conditions such as osteoporosis, which predominantly affects trabecular bone. This knowledge supports the management and treatment of patients at risk of fractures due to low bone density.