New questions have emerged about whether long-term use of bone-building drugs for osteoporosis may actually lead to weaker bones in a small number of people who use them. The concern rises mainly from a series of case reports showing a rare type of leg fracture that shears straight across the upper thighbone after little or no trauma. Fractures in this sturdy part of the bone typically result from car accidents, or in the elderly and frail. But the case reports show the unusual fracture pattern in people who have used bone-building drugs called bisphosphonates for five years or more. Some...