While patients who undergo total knee arthroplasty (TKA) might rejoice after surgery, any instability in the knee would be an unwelcome surprise. New research from the University of Missouri at MU Health Care in Columbia has compared two treatment options, namely a combined tibial and femoral component revision, or an isolated polyethylene liner exchange.
Study Casts Doubts on Isolated Liner Revisions
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Their work, “Isolated Liner Revision for Total Knee Arthroplasty Instability: A Road That Should Remain Less Taken,” was published in the November 23, 2020 edition of the Journal of Knee Surgery.
Co-author James Keeney, M.D., a professor of orthopedic surgery at MU Health Care, told OTW, “Because each hospital has a relatively small number of patients treated for this specific indication, it is valuable for additional studies to either reinforce or to challenge the outcomes. This study confirms the research work that has been published by authors in a few other tertiary care referral centers. Our study supports the observations reported from those other institutions.”
Looking at 20 patients treated with isolated polyethylene liner exchange and 126 patients treated with tibial and femoral component revision surgery from 2011to 2018, the team assessed demographics, comorbidities, time to initial TKA, and reoperation.
Poly Liner Revision Only – No Panacea
Dr. Keeney: “The study identified a high rate of repeat surgery (60%) and early component revision (30%) for patients with knee instability who underwent a simple, polyethylene liner revision surgery.”
“Many surgeons consider exchanging only the plastic liner during revision surgery for patients presenting with knee instability after a total knee replacement surgery. While this is a very basic operation from a technical standpoint and allows patients to recover quickly, it does not adequately treat a substantial proportion of patients with knee replacement instability.”
“While a complete component revision is a major surgery, it is better suited to treat both subtle and severe instability cases. Polyethylene liner exchange is still a reasonable consideration for patients with well positioned and well-fixed implants that are balanced when the knee moves from a straight position (extension) into a bent position (flexion). But it may not be best to pursue this treatment approach solely on the basis of the consideration that it may carry lower surgical risk.”
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Discussion
This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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