The problems associated with drug-coated stents made by Johnson & Johnson are only the latest in several safety scares affecting the booming medical device business. The market for medical devices totals $80 billion per year, and about 20 million individuals in the United States have some type of high-tech device embedded within them. These devices include artificial hips and knees, pacemakers, and heart defibrillators. Of the 80,000 devices in use, most are safe and effective. However, 79 medical devices have been taken off the market since 2001 because of potentially fatal side effects. This represents an increase of 65 percent over the previous five-year period. Another 2,300 medical devices have been recalled for minor complications. Even when a recall occurs, the suspect device remains inside the patient in most cases. Some physicians have started to flag the potential dangers of new implantable medical devices designed to treat back pain, prevent stroke, or soothe serious heartburn. For example, some doctors object to a new metal disk, called the Charite, which has been implanted in the spines of several thousand individuals. It was approved by regulators after being tested in only 304 patients, of which only 36 percent did well enough to stop taking narcotic painkillers. Some physicians and patient advocates blame the problems with medical devices on a medical-industrial complex that comprises lax regulators, 'gadget-happy' surgeons, and greedy consultants.