To Cement or Not to Cement: Have We Answered the Question?: Commentary on an article by Hasan R. Mohammad, MBChB, MRes(Dist), MRCS (Eng), DPhil(Oxon), et al.: "A Matched Comparison of the Long-Term Outcomes of Cemented and Cementless Total Knee Replacements, Based on Data from National Databases. An Analysis from the National Joint Registry of England, Wales, Northern Ireland and the

Abstract

Commentary The debate regarding the optimal method of fixation in total knee arthroplasty (TKA) has continued for almost 40 years, beginning with case series and culminating recently with intermediate-term results from randomized controlled trials (RCTs). The ongoing interest in this debate is justified: TKA patients are getting younger, making implant longevity a priority; post-TKA dissatisfaction remains prevalent, leading to the question of whether implant fixation contributes to pain; and infection is still the most common reason for revision, prompting the desire to simplify surgery and reduce operative time. The popularity of cementless TKA has very recently increased, as reflected in the 2020 annual reports of the Australian Orthopaedic Association National Joint Replacement Registry and the American Joint Replacement Registry. Yet, to date, there have been few long-term (>10-year) large-scale studies that have investigated the clinical outcomes of cemented versus cementless TKA, while accounting for pertinent variables such as age, body mass index, and bone quality. Mohammad and colleagues have challenged this gap in the literature by conducting a rigorous propensity-score-matched cohort analysis of 22,477 patients treated with cementless TKA and 22,477 patients treated with cemented TKA from 2004 to 2018 with Great Britain’s National Joint Registry (NJR). This is the largest long-term matched analysis of TKA outcomes according to fixation type. Their results can be interpreted differently, depending on where your personal loyalties lie. Cement advocates will point out the lower overall implant survival rate, higher rate of reoperation (but not of component revision), and higher rate of revision for pain associated with cementless TKA. Cement cynics will stress the lower infection rate, lower overall reoperation rate, and lower aseptic loosening rate in patients <65 years of age associated with cementless TKA. Regardless of these differences, the study found that both fixation techniques exhibited a survival probability of >95%. Furthermore, historical concerns associated with cementless fixation, including early loosening and periprosthetic fractures, were not observed, nor were older designs associated with higher failure rates. Are the above results enough to encourage the masses to abandon cement in primary TKA? In isolation, probably not. However, the mounting evidence creates a compelling argument. Over the last 10 years, 6 separate RCTs comparing fixation techniques have found little difference in revision rates or survival1-6, at least in the short term. Does the internal consistency of each of these trials apply to your clinical practice? Not universally, but for a young patient who presents with good bone quality, mild/moderate deformity, and no predictors of poor postoperative pain coping, what strong argument exists against attempting cementless TKA? One may be able to point to the observation that cementless components tend to migrate more in the first 3 months to 2 years, but cemented components do so as well, sometimes even to a greater extent7. It is true that several important questions remain: what happens to the current RCT data at intermediate and long-term milestones? Are implant revisions easier with one type of fixation versus the other? Does fixation survival differ in mechanically versus kinematically aligned TKA? Is there an optimal porous surface coverage and keel/stem length that stands above other designs? Evidently, it will take more high-quality studies to answer all of these questions, but that should not necessarily stop surgeons from being selective in their clinical decisions. For now, it is clear that cement is certainly here to stay in primary TKA, especially in older, osteoporotic patients. However, we appear to be headed to what has already happened in hip arthroplasty—a recognition that a one-method-fits-all approach does not work for every patient. I congratulate the authors in helping us get one step closer to this reality.