This article is more than 5 years old. Information may no longer be current.
Mobile-bearing TKAs performed more in Europe than in the United States
More surgeons are using mobile bearings, but there is more evidence for fixed-bearing implants.
Click Here to Manage Email Alerts
While mobile-bearing implants may become more common in total knee arthroplasties in Europe, they will probably still not surpass fixed bearings in the near future, according to one German knee replacement specialist.
“Surgeons in Europe are still divided into proponents and opponents of the mobile-bearing concept,” said Frank Lampe, MD, of the Joint Replacement Center in Hamburg. “The number of mobile bearings might increase in the near future, but I think fixed bearings will still prevail during the next few years because of their excellent clinical results.
“Still, there is no sufficient evidence in the literature that mobile bearings lead to improved clinical results and increased implant longevity,” he told Orthopaedics Today Europe. “I think quality of surgery — for example, the use of navigation systems or minimally invasive approaches — and the skills of surgeons are maybe more important than implant choice.”
Regional differences
Lampe has found that approximately 30% of the 540,000 total knee arthroplasties (TKAs) performed in Europe each year use mobile bearings, but 3% of the 700,000 TKAs performed in the United States involve mobile-bearing implants.
|
Image: Trace R, Orthopaedics Today Europe |
That discrepancy between the two continents exists because there is a broad variety of mobile-bearing implants manufactured by different companies already on the market in Europe, Lampe said. There are far fewer options in the United States, as other implants await approval from the U.S. Food and Drug Administration.
Among the potential advantages of mobile-bearing implants are more physiologic kinematics leading to better functional performance, he said. That function is improved by creating motion patterns such as femoral rollback, rotation and medial pivoting closer to that of the normal knee joint. “This might be a benefit especially for younger and active patients,” Lampe added.
Also, increased bearing congruency with less polyethylene stresses “might result in reduced wear, especially fatigue wear as pitting and delamination,” he said. This is not yet clear for cumulative abrasive wear, especially the additional articulation at the backside of the polyethylene bearings, which is a matter of concern, Lampe added.
Fixation is also enhanced by reduced stresses to the implant-bone fixation interface due to decreased intrinsic constraints, he said.
Disadvantages and questions
One open question is whether reduced implant constraints in mobile-bearing knees lead to better implant fixation at the implant-bone interface and increased implant longevity, he said.
While mobile-bearing implants are an appropriate and well-established option for the experienced knee surgeon to treat the young and active patient, their clinical benefits compared to fixed-bearing designs have yet to be proven, he said.
“Theoretically, advantages with regard to function, wear and fixation are obvious,” he said. “However, clear clinical benefit is not yet evident. Both concepts lead to good clinical results and implant longevity.”
Proper surgical technique with regard to alignment, implant positioning and soft tissue management is generally more important for the outcome than implant choice, he added.
For more information:Reference:
- Frank Lampe, MD, can be reached at the Joint Replacement Center, Klinikum Eilbek-Schoen Kliniken, Dehnhaide 120, D-22081 Hamburg, Germany; +49-89-6211-0; e-mail: flampe@schoen-kliniken.de. He is a member of the B. Braun/Aesculap speakers’ bureau.
Lampe F. Mobile-bearing implants: The European perspective. Presented at the 9th Annual Advances in Arthritis, Arthroplasty and Trauma Course. Sept. 10-12, 2008. Arlington, U.S.A.