Our bones lose mass at a rate of about 1 percent a year from late middle age onward, which is of course why elderly people and broken bones are so unhappily synonymous. Broken hips are especially challenging for the elderly. About 40 percent of people over seventy-five who break their hips are no longer able to care for themselves. For many, it is a kind of last straw. Ten percent die within thirty days, and nearly 30 percent die within twelve months. As the British surgeon
