Much of the available data regarding metal-on-metal (MoM) hip implants, including registry data, comes from countries outside the U.S. Although the safety concerns for patients who have or may be considering MoM hip implants are present throughout the world, there are differences between usage of MoM hip implants in the U.S. and those outside the U.S.
In June 2012, the FDA asked members of the FDA’s Orthopaedic and Rehabilitation Devices Advisory Panel meeting to discuss these differences and the following points were highlighted:
- Device Availability - There may be physical differences between a device marketed in the U.S. and a device marketed outside the U.S. under the same name. Also, devices used in other countries may not be available in the U.S., and among devices available around the world, device popularity and usage vary. There may also be substantial differences in the practice of “mixing and matching” implant components between the U.S. and other countries.
- Health Care System - National guidelines regarding patient eligibility for hip implants can result in differing timeframes between diagnosis of a patient’s underlying hip disorder and hip replacement surgery. For example, patients outside the U.S. may wait longer to receive a hip implant. This could mean patients are treated at a later stage of disease and/or later age, which will impact the device selected for treatment and the outcomes of hip surgery.
- Practice of Medicine - Surgeon experience and training programs differ between countries. In the U.S. there is greater variety in surgeon experience and hospital volume in comparison to some other countries, where hospitals are more focused on certain types of procedures. In the U.S., approximately half of all primary hip replacements are performed by surgeons who typically do fewer than 15 to 20 of these surgeries per year.
- Population - Factors including a patient’s age, sex, weight, diagnosis and activity level influence the lifespan of a device. These factors may vary more in the U.S. population than in other countries, which may influence the outcomes of hip surgery including the revision rate or implant survivorship (need to remove implant and put another in its place).
- Patient Expectations - Patients may have different expectations for the longevity and performance of their MoM hip implants, which underscores the importance of surgeon and patient discussions prior to surgery.
When comparing U.S. patients to those in other countries, it is important to be aware of the differences. Since much of the available data are from countries outside the U.S., the data are not necessarily indicative of U.S. outcomes. The FDA launched the International Consortium of Orthopaedic Registries (ICOR), an international collaborative effort that aims to address differences in orthopaedic registries around the world and allow for collaboration to harmonize and utilize the data available from these registries.