This week’s Orthopaedic Crossfire® debate was part of the 35th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “The Cementless Tibia: A Viable Fixation Alternative.” For is R. Michael Meneghini, M.D., Indiana University School of Medicine, Indianapolis, Indiana. Opposing is Gwo-Chin Lee, M.D., University of Pennsylvania, Philadelphia, Pennsylvania. Moderating is Robert E. Booth, Jr., M.D., Jefferson Health 3B Orthopaedics, Philadelphia, Pennsylvania.
Dr. Meneghini: Cementless fixation is a viable alternative on the tibial side. My disclosures are relevant because I have multiple implants that I’ve designed that are on the market and receive royalties for them.
Why cementless knees? Why is there a debate where we’re talking about it? We all know that there’s established long-term success by way of biologic fixation. We have now improved our biomaterials for fixation and wear. Regarding cementless failures from years ago, we corrected those mechanisms and we do have the ever-increasing demand for operating room efficiency. Patients are younger and more active. I’ll argue that cement is not the durable interface for those patients.
If you look at multiple survivorship studies, Rich McCalden in over 6,000 consecutive knees (McCalden, et al., JOA, 2013). The California database, over 120,000 knees (Meehan, et al., JBJS-Am, 2014), both studies showed conclusively a decrease in survivorship with aseptic loosening in younger, more active patients using cement.
Cement is not a durable interface long term. A published retrieval study showed that the bone pulls away from the cement over time. (Miller, et al., CORR, 2014).
We originally looked at this with Merrill Ritter years ago, looking at a small group that he had performed cementless originally back in the early 1980s, and followed those patients out to 20 years. He only had two failures and had a 97% survivorship at 20 years. That equaled his survivorship in the cemented AGC cohort, and there was a selection bias. Those cementless patients were younger by over a decade. And when we looked at those x-rays out to 20 years, we were impressed with the pristine radiographic interfaces (Ritter, et al., JOA, 2010). We saw them over and over again. Biologic fixation stood the test of time even in those young patients.
Mike Dunbar gets a lot of credit for helping us understand how these implants behave early, and using RSA data, we can risk-assess these patients for their longevity. He looked at 28 porous tantalum tibias and showed that at 2-year follow-up none were at risk for failure compared to the cemented counterparts where 4/21 were at risk. When he performed a 5-year follow-up on the cementless cohort, there was no further migration (Dunbar, et al., JBJS-Am, 2009).
A Cochrane database review followed up on that and looked at a meta-analysis showing the exact same thing (Nakama, et al., Cochrane Database Review, 2012). We know that press fit knees, particular to the tibias, will settle up to 1mm or 2mm over the first 2 years and then stabilize. Once they stabilize, it is a much more durable interface than cement. This is shown over and over again in RSA data. I would argue that cementless fixation is appropriate for younger patients.
The Mark Coventry Award paper out of Mayo Clinic looked at a porous tantalum design involving 397 patients in a randomized controlled trial. There were no failures at a minimum of 5-year follow-up in that cementless tibial design (Pulido, et al., CORR, 2015).
We are in the era of improved biomaterials—hydroxyapatite, peri-apatite, porous tantalum, and porous titanium.
I believe there is sufficient evidence to support cementless fixation. How do we continue expanding that and doing it safely? I do believe that patient selection is important. There are gender differences. An older female, I think cement works great. Probably no reason to do a cementless fixation in that particular patient. But younger people, people with good bone, I think are appropriate. And you’ve got to be a little bit cautious in those who have poor bone quality.
We have biomechanical support for that. We looked at this in a biomechanical model and regardless of the design, if the bone quality is poor the mechanical integrity may be less. I would just use caution in the older, osteoporotic patients (Meneghini, et al., J Knee Surg, 2011).
I also believe there are critical implant design factors and surgical techniques.
I think now we understand what makes a successful press fit tibia. You either have a robust central keel or post and peripheral fixation of some kind. It can be a cruciform peg or screws, whatever your choice is. But that will be a successful design or central hex pegs which have also been shown over and over again to be successful. Modern testing has evolved, which is why we have more confidence in these modern designs.
