The study also showed women who had metal on metal implants had almost twice as many problems as men. Experts say the FDA should require more testing on hip implants to find out which ones work best with women's bodies and will last 15 to 20 years.
Researchers say the smaller implants used in women involve a smaller ball in the socket, which can dislocate more easily.
More than 300,000 Americans undergo total hip replacement surgery every year. The overwhelming majority of these operations - up to 98 percent -- are successful.