This week’s Orthopaedic Crossfire® debate was part of the 18th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “The Cementless Knee: An Emergent Game Changer.” For is Matthew P. Abdel, M.D., Mayo Clinic, Rochester, Minnesota. Opposing is Gwo-Chin Lee, M.D., University of Pennsylvania, Philadelphia, Pennsylvania. Moderating is Thomas S. Thornhill, M.D., Brigham and Women’s Hospital, Boston, Massachusetts.
Dr. Abdel: We are all aware that there is good long-term survivorship with cemented primary total knee arthroplasty at approximately 90% at 15 years. However, there are multiple concerns with the contemporary patient, three of which I am going to articulate here today.
First and foremost, our patient profiles are changing; patients are younger, more active and living longer. In addition, the obesity epidemic is significant not only in the United States but across the world, and multiple studies have shown increased failure with cemented total knee arthroplasties in obese patients.
It is my contention that cementless total knee arthroplasty is an attractive option for three main reasons.
One, there is potential for improved longevity particularly in younger, more active patients.
Two, there is potential for improved longevity in obese patients which is a significant portion of our practice.
And three, there is potential for decreased operative time which is essential in the cost-conscious, bundled-care model.
So why now? There have been multiple modifications to implant design and surgical technique that make it possible. These include highly porous metals, 3D printing, and a fundamental understanding of the surgical technique required to execute cementless total knee replacements.
Let’s break it out into three main areas.
Longevity—we are targeting biologic fixation—very similar to an uncemented total hip replacement. Take for instance a review of 5 Level I randomized clinical trials with 300 patients (Nakama, et al., Cochrane Database Syst Rev. 2012). While the authors did find a greater displacement in tibias from a cementless design early on, they found that the risk of future aseptic loosening with cementless total knee arthroplasty was one half of that of cemented fixation – again, Level I data.
If you look at a summary of the cementless knee literature, particularly a study by Meneghini and Ritter (J Arthroplasty, 2010), you find 98% survivorship at 20 years.
Moreover, we have contemporary implant designs. At the Mayo Clinic we conducted a Level I, randomized clinical trial of three implant designs 2003 to 2006 (CORR 2015). We randomized 400 patients into one of three groups; cemented modular, uncemented monoblock trabecular metal, or cemented monoblock trabecular metal.
Looking at the survivorship, we found no significant difference at 5 years but I’d like to highlight: once you have biologic fixation early you can anticipate longevity whereas with cemented fixation you anticipate degradation over time.
What about obese patients? In a study we published in 2015 (J Arthroplasty) we showed that obese patients with cemented total knee arthroplasties had a greater rate of aseptic tibial loosening with a cutoff BMI being approximately 35. When we stratified it based on cumulative probability patients had a two-fold increased risk of failure with a BMI greater than 35 in a cemented construct.
