In 2001, in European and American regulatory agencies recalled millions 
of zirconia ball heads sold under the commercial name Prozyr by Saint Gobain Ceramiques Desmarquest. These heads are one of the important components used in a total hip replacement procedures also known as arthroplasty. This recall happened because the femoral ball heads were fracturing and failing at inordinately high rate after implantation in patients in a relatively short period of time. What followed was an intense international investigation by a panel of experts. The company and regulatory agencies wanted to find out answers to two central questions as soon as possible. What caused these fractures that led to the failure of these implants? What changed that caused this sudden jump in failure rates?