Which site is referred to as the distal site in bone density measurement?

In bone density measurement, the term "distal site" commonly refers to a specific location on a bone where measurements are taken, particularly in the context of dual-energy X-ray absorptiometry (DXA) scans. The distal site is usually associated with the area of the forearm, specifically the distal radius or the distal ulna, which is approximately 10% from the wrist, or more broadly around the distal metaphysis of the radius. This region is significant in assessing bone density because it is often the first site to show changes in bone mineral density with conditions such as osteoporosis.

Since the question refers to the distal site in the context of percentage distances, the choice that indicates 10% is aligned with the conventional anatomical reference point for assessing bone density at the distal site. Thus, it is the most accurate choice among those offered when considering the standard practices of bone density measurement.