CORR Insights®: Custom Implants in TKA Provide No Substantial Benefit in Terms of Outcome Scores, Reoperation Risk, or Mean Alignment: A Systematic Review

Where Are We Now?

New technology can advance our field and improve patient care. The introduction of highly crosslinked polyethylene (HXLPE) for THA remains the single most impactful advancement in my career as an arthroplasty surgeon. Highly crosslinked polyethylene has all but eliminated osteolysis as a complication and contributed to the expansion of indications for hip replacement [10]. Despite its relatively low cost and good overall results, it still took years of experience and the accumulation of clinical evidence to fully understand HXLPE’s value.

But not all new technology lives up to its promise. The idea of custom knee implants for routine TKA, for example, makes some intuitive sense. A custom knee implant should theoretically offer a better fit, thus reducing soft tissue irritation and improving kinematics. In turn, the patient should feel less pain, have improved function, and ultimately, more overall satisfaction. Custom knee implants for routine primary TKA were initially FDA approved through the 510K process in 2006 [13], giving researchers more than sufficient time to assess the value of these implants for our patients and to our healthcare system.

With their systematic review, Beit Ner and colleagues [2] did just that and found that custom implants for routine primary knee replacement have “generally poorer outcomes scores for pain and function, generally higher risks of reoperation and reintervention, and no overall benefit to alignment” when compared to standard off-the-shelf implants. Based on these findings, the authors recommended against the routine use of custom TKA components. On this point, I strongly agree with the authors. Until or unless custom TKA implants demonstrate benefits that patients can perceive in well-designed trials, they should not see common use.

Where Do We Need To Go?

We all want to improve TKA for our patients. It is commonly stated that 20% of TKA patients are dissatisfied [3], though a recent systematic review on this topic found that among 138 studies reporting overall satisfaction after TKA, the median reported percentage of satisfied patients was 88.9% [9]. Still, satisfaction does not appear to have changed substantially over decades [3, 4, 8] despite many changes that have occurred in implant design and surgical technique over that period of time. Could it be that there is still a purely surgical, implant, or technique-related solution to post-TKA dissatisfaction that we have thus-far missed? Possibly, but I think we also need to look for and implement other solutions. Furthermore, because technological innovations in TKA are not assured to be advances, we need to be mindful of how we adopt new technology and how we present new technology to our patients.

How Do We Get There?

Our first task is to discover ways to increase the proportion of patients who are satisfied with their TKAs. Innovation is important to the advancement of our field, but technical modifications to the implant or to the surgery may not reliably afford a solution. The bar is high, as TKA is already a very successful operation overall. The Food and Drug Administration’s device approval process is the first check on new device safety and effectiveness, but this process is not perfect and does not address whether the intervention will result in improvement rather than simply equivalence with existing devices. Our charge as responsible orthopaedic surgeons and advocates for our patients is to base our practice on a critical evaluation of relevant research and registry data. We must seek improvements over current standards.

Also, we should avoid the temptation to focus only on the surgical intervention. It may be that there are other ways to intervene, pre- and postoperatively, to improve satisfaction and outcome in TKA. Multiple preoperative factors have been associated with low postoperative satisfaction such as preoperative depression, preoperative opioid use, unrealistic preoperative expectations, and poor communication [1, 5-7]. Perhaps interventions on factors such as these can be more impactful on subjective TKA outcomes and less costly than introducing new technology.

Finally, I believe that to maintain a position of trust with our patients and with the public we must be responsible with marketing. Unfortunately, new technologies are or have been marketed by hospitals, medical groups, or surgeons as advances when data are insufficient to reach such conclusions, or when associated risks are minimized [11, 12]. We must not perpetuate this problem as it harms our profession and our standing in society. Improper marketing harms the responsible introduction of technology, is a stain on our profession, and does not serve the best interests of our patients.