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Bilateral study finds similar results with fixed and mobile-bearing TKA at 13 years
Investigators also found 15-year survivorship rates of 97%-98% for these implants.
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SAN DIEGO — While the theoretical advantages of mobile-bearing knees include less wear and better clinical results than fixed-bearings, a new study reveals similar clinical and radiographic outcomes at long-term follow-up.
In a prospective, randomized trial, Korean investigators studied 146 patients who underwent simultaneous bilateral total knee arthroplasties (TKAs) with the Low Contact Stress (LCS) Mobile-Bearing Knee System in one knee and the Anatomic Modular Knee (AMK), a fixed-bearing implant, in the other [both DePuy].
A mean follow-up of 13.2 years revealed similar mean Knee Society (KS) scores, Hospital for Special Surgery (HSS) scores, functional scores and activity scores for the AMK and LCS groups.
The investigators also discovered no radiographic evidence of osteolysis in either group.
“Although there is no evidence to prove the superiority of the mobile-bearing TKA over the fixed-bearing TKA, the clinical and radiographic results of both types of the TKA were encouraging in long-term follow-up,” Young-Hoo Kim, MD, said.
Evaluating patients
The study included patients with a mean age of 69.8 years. Most were women, and 94% had a preoperative diagnosis of osteoarthritis.
Surgeons cemented the fixed- and mobile-bearing knees and used all-polyethylene patella components. They evaluated patients using KS and HSS scores, and performed radiographic assessments with CT scans and fluoroscopy. During follow-up, they attempted to detect polyethylene wear, osteolysis, component loosening and position change.
Few complications
The investigators reported a mean KS score of 92 for the AMK group and 90 for the LCS knees at final follow-up. The groups also showed similar functional scores.
Five knees in the AMK group underwent revision for polyethylene wear, infection and loose tibial components.
Three knees in the LCS cohort were revised for instability, and one underwent revision for infection. Using revision as an endpoint, Kim and his colleagues found a 15-year Kaplan-Meier survivorship rate of 97% for the AMK group and 98% for the LCS group.
They also discovered 99% survivorship for the AMK TKAs and a 100% rate for the LCS implants using loosening as an endpoint.
For more information:Reference:
- Young-Hoo Kim, MD, can be reached at DongDaeMun Hospital, Ewha Womans University, The Joint Replacement Center of Korea, 70, ChongRo 6-Ga, ChongRo-Gu, Seoul, 110-783, Republic of Korea; +82-2-760-5000; e-mail: younghookim@ewha.ac.kr. He has no financial interest in any products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Kim YH, Kim JS, Kim DY. Long-term results of fixed-bearing and mobile-bearing total knee arthroplasties. #14. Presented at the American Academy of Orthopaedic Surgeons 74th Annual Meeting. Feb. 14-18, 2007. San Diego.