What percentage of cortical bone does 33% of the radius or ulna contain?

• A. 75%
• B. 85%
• C. 99%
• D. 100%

Answer: (C)

The content of cortical bone in long bones, such as the radius and ulna, is typically determined based on the specific percentage of the total cross-sectional area measured at a particular site. In the context of bone densitometry, the radius or ulna is a critical site for assessing bone health, particularly in relation to conditions such as osteoporosis.

When we refer to 33% of the radius or ulna, it is recognized that this parameter represents a proportion measured at a certain point along the bone, which is often related to an area known for having a dense cortical shell. At this specific distal site, the cortical bone predominates and is found to account for almost the entirety of the bone tissue present.

The answer indicates that at a measurement site that represents 33% of the radius or ulna, there tends to be a near-complete amount of cortical bone, which is understood in the field to encompass about 99% of the volume at this region. Consequently, 99% accurately represents the amount of cortical bone present in this cortical area when imaging or assessing bone density in this location. This information is essential for interpreting bone health and assessing fracture risk in patients.

In summary, the percentage of cortical bone within 33% of the