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Future TKA may see ‘smart’ implants and new alternative bearing surfaces
Barriers to implementing smart implant technology include cost, regulations and limited applications.
Although total knee replacement using cobalt chromium femoral components and polyethylene tibial components show a high long-term survival rate, surgeons continue to look for solutions to wear and suspected metal allergy, and attempt to gain information directly from the implant.
At the 9th Annual Advances in Arthritis, Arthroplasty and Trauma Course, Jean-Yves Jenny, MD, and William M. Mihalko, MD, PhD, discussed innovative alternative bearings for total knee replacement (TKR) and smart implants.
New alternative bearing surfaces could help surgeons improve the quality of their results, Jenny said.
Gold standard
“I would say that the current gold standard remains the cobalt chromium femoral component sliding on a standard polyethylene component,” he said. “Highly crosslinked polyethylene may be more frequently used in the future, when the cost increase is contained. This might be the case because the technology of polyethylene is not very costly. On the other hand, alternative materials for femoral components might remain experimental because of the problem of increased cost, except for patients with allergy problems.”
The main problem with the current gold standard is polyethylene (PE) wear. While some researchers have found that highly crosslinked PE has lower wear rates than conventional PE, different manufacturing techniques cause variance between PE components, Jenny said.
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Image: Jenny J-Y |
Femoral implant
“Currently, the only real alternative for the metallic femoral component is alumina,” he said. Jenny cited a study by Yasuda and colleagues that investigated an alumina femoral component with a conventional PE gliding surface. The investigators noted that the alternative might exhibit good wear resistance.
Research by Majima and colleagues found comparable clinical results between a posterior cruciate ligament-retaining implant with an alumina ceramic condylar prosthesis and a cobalt-chromium femoral component.
Zirconium-coated components could provide another alternative. Jenny noted that an in vitro study from researchers in Japan found that zirconium-coated femoral explants were not destroyed by a PE gliding surface.
“There is some clinical use and early clinical results that are encouraging points, but there are also some negative points with zirconium-coated femoral components,” Jenny said. He noted research by Göbel and colleagues that found a statistically significantly higher rate of radiolucent lines at the tibial site when using these implants.
New multilayer-coating techniques may also solve metal allergy problems. Jenny noted that research investigating cobalt chromium femoral components coated with zirconium and an additional coating of chromium nitrate avoided allergy complications and showed decreased PE wear.
“Perhaps it might be a solution to cure both the problem of allergy and the problem of wear,” Jenny said. “It is only experimental at the moment, but it may be an interesting way for the future.”
“Smart” implant
In addition to developing new alternative bearings, some researchers are investigating the use of “smart” implants to improve TKR.
“A smart implant is anything that is going to communicate information to the heath care provider,” Mihalko said. “That information can be anything from the serial and catalog number of the implant to forces, wear and number of gait cycles, which can give the surgeon some type of idea if that patient is starting down a pattern of aseptic loosening or severe wear.”
Radiofrequency devices in implants could make it easier to track patients who move. Smart implants could also help surgeons identify patients with recalled implants and predict prefailure patterns that could allow an earlier intervention to increase the longevity of the knee replacement, Mihalko told Orthopaedics Today Europe.
He said only one smart load-sensing device has been implanted, which was much larger than a typical primary knee replacement with a longer stem on the tibial baseplate. The custom implant, developed by Darryl D. D’Lima, MD, PhD, and colleagues, carried a six-figure price tag.
“Certainly, cost at this point would be a huge overriding factor, and the benefit is going to have to be significantly proven and the cost significantly decreased before we get there,” Mihalko said. ote
For more information:
- Jean-Yves Jenny, MD, can be reached at Centre de Chirurgie Orthopédique et de la Main, Hôpitaux Universitaires de Strasbourg, 10 Avenue Baumann, F-67400 Illkirch-Graffenstaden, France. 33-3-885-52145; e-mail: jean-yves.jenny@chru-strasbourg.fr. He receives royalties and consulting fees from B. Braun/Aesculap.
- William M. Mihalko, MD, PhD, can be reached at Campbell Clinic Orthopaedics, University of Tennessee School of Medicine, Department of Orthopaedic surgery, 1458 West Poplar Ave., Collierville, TN 38017 U.S.A.; +1-901-759-5512; e-mail: wmihalko@campbellclinic.com. He receives consulting fees from Aesculap and Ethicon and does contracted research for Stryker and Aesculap.
References :
- D’Lima DD, Steklov N, Patil S, Colwell CW Jr. The Mark Coventry Award: In vivo knee forces during recreation and exercise after knee arthroplasty. Clin Orthop Relat Res. 2008;Jun 19:Epub.
- Göbel F, Ulbricht S, Hein W, Bernstein A. Radiological mid-term results of total knee arthroplasty with femoral components of different materials. Z Orthop Unfall. 2008:146(2):194-199.
- Jenny JY. Alternative bearing: Futuristic options in TKA. Mihalko WM. Smart implants. Both presented at the 9th Annual Advances in Arthritis, Arthroplasty and Trauma Course. Sept.10-12, 2008. Arlington, U.S.A.
- Majima T, Yasuda K, Tago H, Aoki Y, Minami A. Clinical results of posterior cruciate ligament retaining TKA with alumina ceramic condylar prosthesis: comparison to Co-Cr alloy prosthesis. Knee Surg Sports Traumatol Arthrosc. 2008;16(2):152-156.
- Yasuda K, Miyagi N, Kaneda K. Low friction total knee arthroplasty with the alumina ceramic condylar prosthesis. Bull Hosp Jt Dis. 1993;53(2):15-21.