A drug used to treat severe osteoporosis promotes healing of hard-to-mend fractures in the elderly and others, reducing pain and time spent in nursing, researchers said Tuesday.

In preliminary studies, 93 percent of 145 patients who had unhealed bone fractures — some for as long as six months — had significant healing after only eight to 12 weeks on the drug, called teriparatide, or Forteo.

An estimated 5 percent of the 6 million fractures suffered by Americans each year are slow to heal or do not heal at all, and as many as a quarter of the elderly with pelvic and hip fractures die within a year as a result of their injuries.

Others with such injuries enter nursing homes never to come out again, so the drug has great promise for reducing medical costs and improving quality of life, said Dr. Susan Bukata of the University of Rochester Medical Center, lead author of the study.