Mayo Total Joint Registry 20-year study reveals variation in implant survival
New implantable devices can never reach clinical use without some level of uncertainty about their effectiveness and overall safety, despite the best possible safeguards and pre-market regulatory requirements. This is particularly true because many will be required to function for decades following implantation. Therefore, post-marketing studies of implantable devices are essential to continually evaluate the performance of such implants in the real-world environment, as it may be years or decades before we can truly assess their effectiveness.
"For this reason, large databases or registries of patients, such as the Mayo Total Joint Registry, have an essential role to play in the monitoring of medical implants," explains David G. Lewallen, M.D., an orthopedic surgeon at Mayo Clinic in Rochester, Minn.
In a recent study using data extracted from the Mayo Clinic Total Joint Registry, Dr. Lewallen and a Mayo team of orthopedic surgeons compared the long-term performance of 20 different types of uncemented acetabular components. They analyzed 9,584 total hip procedures performed at Mayo Clinic between January 1994 and December 2004. Published in the September 2011 issue of The Journal of Bone & Joint Surgery, the study is the largest of its kind in the U.S. of American-made implant components used in hip arthroplasty.
Hilal Maradit Kremers, M.D., an epidemiologist on the study, notes, "To find out how patients are really doing and how the devices are performing, you need to watch for changes over long periods of time, not just for a few months or years following surgery. You need to allow enough time for the implants to begin to wear or become unstable."
Study results show that long-term survival differs significantly among the different types of uncemented acetabular components following primary hip arthroplasty — and that newer designs are not inherently better than older ones. For example, implants designed in the 1990s do not perform significantly better than one of the earliest models (the Harris-Galante I acetabular cup) introduced in the early 1980s.
Notably, most revisions occurred in the second decade following the initial hip arthroplasty. This indicates that implant performance in the real-world setting needs to be continually assessed through long-term follow-up. In many circumstances, follow-up beyond five to seven years is needed to determine real differences between designs as reflected in the survival of implants that remain free of revision due to complications such as aseptic loosening, wear and bone loss due to osteolysis.
Dr. Lewallen says there are three key take-home messages from the study that orthopedists need to consider in planning for best outcomes:
- Newer, typically more expensive implants, may not necessarily be better than older implant designs.
- Performance differences between implants often only become obvious after five to seven years of follow-up. So, shorter term studies may be inadequate to capture differences in failure rates across different implants.
- Revisions due to excessive polyethylene wear have been a major clinical problem with modular uncemented designs in the past, validating clinical interest in improved bearing materials.
The role of orthopedic registries
Registries are important for examining the effectiveness of orthopedic implants that have limited pre-market performance information. The Mayo data come at an important time for a large initiative now under way in the U.S. to establish a comprehensive nationwide orthopedic registry to gather data on joint replacement and revision surgeries.
The American Joint Replacement Registry (AJRR) is a project initiated by the American Academy of Orthopaedic Surgeons. It is being developed in collaboration with a range of stakeholders, including orthopedic surgeon associations and professional societies, orthopedic industry partners, private payers, and public representatives.
The AJRR has just completed a pilot project with data collection establishing methods that are being used to expand operations nationally. As with other national registries around the globe, the goal of the AJRR is to improve patient safety, enhance the quality of care and reduce cost. As chair of the AJRR board of directors, Dr. Lewallen views the Mayo data as a useful example of the vital role that registry data can play in improving care.
A well-designed, fully staffed long-term nationwide registry could provide:
- Reliable information on a large scale that would enable more rapid improvement in orthopedic care in the United States
- Standardized data on hip and knee implants by model that could enable orthopedic surgeons, device manufacturers and hospitals to analyze outcomes for insight into what determines the success or failure of such devices
- Insight to help inform decisions on where to deploy research and resources to improve performance
Dr. Lewallen comments, "The kinds of comparisons a well-run registry makes possible can help identify opportunities for improvement. And that's the goal we all share — surgeons, patients, device manufacturers, hospitals and insurance companies alike." The AJRR can also serve as a resource for patients in retrieving information on their own specific surgery and the device that they had implanted during their operation. At present, this information is not easily available to patients.