Nobody familiar with American medical care in the 21st century should be surprised that a 73-year-old woman can be minutes away from getting a painful collapsed vertebra filled with liquid plastic and it's impossible to say whether the procedure works, or how. It may be that Marcia Henry could get as much relief from injections of local anesthetic, from physical therapy or just from more time to heal as she will from the $3,137 "vertebroplasty" she's about to undergo at the University of Virginia Medical Center in Charlottesville. "The studies have been contradictory. Which one trumps which one? We don't know," says interventional radiologist Mary E. Jensen as she sits in a dimly lit X-ray viewing room and watches a colleague lay out a tray of instruments in a procedure suite next door. "It leaves the treating physician in a dilemma." American medical care is rife with such treatments, whose usefulness is uncertain not just to the doctors who deliver them but also to the patients who receive them.