CORR Insights®: Can Technology Assistance be Cost Effective in TKA? A Simulation-based Analysis of a Risk-prioritized, Practice-specific Framework

Where Are We Now?

We are in an exciting phase in the technological evolution of total knee arthroplasty (TKA). A number of technology-assisted TKA (TA-TKA) approaches using computer navigation, patient-specific instrumentation, or robotics have been proposed to improve the implant position and alignment and, ostensibly, the clinical results of TKA. However, although some studies have found that using TA-TKA improves the precision by which the planned coronal alignment is achieved [4, 5, 8], this has not resulted in a decrease in the revision rate or an improvement in function in the long term compared with conventional TKA. Because it is expensive and requires more intraoperative time than conventional TKA, there are concerns of time and cost efficiency with the use of TA-TKA. There are also other risks, such as the uncertainty and potential harms associated with novelty itself [3, 7]. Proponents of TA-TKA have suggested that with increased use and surgical experience, these technologies would reduce the risk of revision and mitigate the concerns of cost and time efficiency [11]. However, considering that TKA has low revision rates with or without technology assistance, a clinical trial evaluating the efficacy of TA-TKA compared with that of conventional TKA to reduce revision rates would need a sample size of several thousands of patients. Such a trial would be a mammoth task requiring substantial financial and human resources dedicated to ascertaining the efficacy of a modality that so far has shown to be ineffective for improving clinical outcomes.

What if there was a way to simulate a large-sample study using modern advancements based on the available evidence, using baseline variables and published clinical outcomes of patients who had TA-TKA and those with conventional TKA? An earlier computer simulation study by Hickey et al. [2] did exactly that; they wanted to predict whether TA-TKA, owing to its precision in implant placement, would reduce the revision risk and be cost effective. Although such simulation studies have been done before with differing results regarding the cost-effectiveness of TA-TKA [10, 11], Hickey et al.’s study [2] was convincing. It found that studies enrolling all-comers would have to be impracticably large to find any benefit to the added technology. This fits well with what we have seen in the trials I mentioned; perhaps there would be improvement in alignment, but no differences in revision favoring the expensive new technology in unselected populations.

But what would happen if we focused our attention on patients who are at a higher risk of undergoing premature revision? I’m referring to factors such as younger age, higher BMI, and perhaps men. This is what Hickey et al. [3] explored in an exciting follow-up study, published in this month’s Clinical Orthopaedics and Related Research®. Using computer simulation, the authors evaluated data of 20,000 TKAs by randomly assigning high-risk and low-risk variables. Differences in patient-specific reductions in the revision risk and change in quality-adjusted life were predicted for 5000 simulated operations per patient using the reported precisions of the three TA-TKA techniques (navigation, patient-specific instrumentation, and robotic), conventional TKA technique, and an ideal TKA with neutral coronal alignment. The authors did not find enough potential benefit in the low-risk groups to make a further inquiry worth considering, but their simulations suggested that in an elevated-risk population, a practice size of 100 patients per year who would meet their criteria as being at a higher risk of revision could experience cost-effectiveness with navigation and robotic TKA, with use percentages of 6% and 20%, respectively. Thus, it certainly seems like a potentially helpful intervention. However, as a simulation, one would not want to draw strong clinical inferences or use this to implement expensive new technology in practice. Rather, these findings suggest that future clinical trials might best be designed by and performed in high-volume centers in patients with a higher risk of revision (younger age, more men, and higher BMI), because that is where we might expect to see the largest impact of these new tools. If that proves true, in these settings, implementation of these approaches would make the most medical and economic sense.

Where Do We Need To Go?

There are two key topics to discuss in the current scenario of TA-TKA. One is its use in clinical practice. The second is further research development in this field to explore whether and how these modalities would be effective. As a scientific community, our recommendation for widescale use of any assisted modality for TKA to further improve clinical results compared with conventional TKA would logically require appraisal in two steps (at a minimum). The first is to have proof of improvement in long-term survivorship and patient-reported outcomes with the use of TA-TKA compared with the conventional approach to TKA. The second step would be to evaluate the cost-efficiency of these expensive modalities. Randomized controlled trials [4, 5, 8] that evaluated the long-term clinical results in terms of survivorship and validated patient-reported outcomes, as well as a meta-analysis evaluating patient-reported outcomes [1], found no advantage of navigation, patient-specific instrumentation, and robot-assisted technology for TKA over conventional TKA. It makes less sense to worry about the cost-effectiveness of a modality that has not proven to be effective. Hickey et al. [3] help us realize that TA-TKA may not help to reduce the revision rates and might prove cost effective in the usual patients who undergo TKA (older women). The study showed TA-TKA had modest yet promising effectiveness in patients with an elevated risk. Instead of asking whether TA-TKA is effective, should research be directed toward a select group of patients with an elevated risk of revision?

The predictions of cost-effectiveness in the study by Hickey et al. [3] assume that TA-TKA achieves coronal alignment of ± 2.4° using patient-specific instrumentation, ± 1.9° using navigation, and ± 1.0° using robotic modalities. Should the use of TA-TKA be restricted to higher-volume centers, and should it be performed by surgeons with expertise in TA-TKA to replicate stringent coronal alignment targets? Do high-volume surgeons, most of whom are experts in conventional TKA, even need TA-TKA to help them achieve the coronal alignment targets? Going back one step, TA-TKA was marketed to novice and low-volume surgeons to replicate intraoperative alignment on par with their experienced colleagues. Further, performing TKA requires an understanding of soft tissue balancing apart from bone resection. Unlike navigation and patient-specific navigation, robot-assisted TKA gives feedback regarding gap balancing across motion. However, it is not uncommon for surgeons to revise cuts made using TA-TKA if they are not satisfied with the gap’s balance [9]. A novice surgeon could overlook these intraoperative corrections, leading to poor outcomes after TA-TKA. It seems TA-TKA would not be effective to reduce the revision risk and cost effective for novice surgeons and low-volume practices. If experienced surgeons and high-volume practices may not need TA-TKA and novice surgeons and low-volume practices can’t afford it and could still make judgement errors while using it, what is the future of TA-TKA in clinical practice?

How Do We Get There?

In light of this convincing evidence suggesting that the use of expensive TA-TKA modalities could be cost effective only when employed at high-volume centers and in select patients, it is imperative to think of tough yet plausible organizational changes. Patients with multiple factors contributing to an elevated risk of revision—perhaps younger patients, active men, those with obesity, those with large-joint deformities, patients with prior trauma and periarticular implants, and those with extraarticular deformities—could be referred to high-volume centers equipped with TA-TKA. Less-experienced surgeons and low-volume practices could focus on performing conventional primary TKA in patients with a lower revision risk. This will help to accumulate higher proportions of patients with an elevated revision risk at specialized centers and facilitate research related to the efficacy of TA-TKA in patients with a higher risk of revision. Such organizational changes will require modifications to current compensation models for complicated TKA and sincere effort from orthopaedic communities [6]. Along with the revision rate, future research should focus on more rigorous tools to evaluate the efficacy of TA-TKA from patients’ perspectives by using effect-size metrics of minimal clinically important differences and substantial clinical benefits in patient-reported outcome scores.

In terms of individual clinical practices, the narrative during patient and surgeon education should clarify that despite improvement in the precision of implant placement, a radiographic difference doesn’t seem to result in any perceptible clinical benefit. The last thing we want is to make the well-performing conventional TKA technique look bad just because new technology results in better angles on a goniometer or prettier radiographs. This could help decrease pressure on surgeons and institutions to adopt, and for patients to choose, TA-TKA over conventional TKA. And, of course, it is also imperative that surgeons in training should become skillful in conventional TKA even if their institution uses TA-TKA, because the best-available evidence suggests there are no patient-perceptible benefits of TA-TKA in the typical patients who undergo TKA. Nonetheless, a knowledge of conventional TKA is invaluable to surgeons; even if TA-TKA is used, gap balancing may not be optimal and might result in either revision of the bone cuts or soft tissue release. Only time will tell whether TA-TKA will be a valuable tool in a surgeon’s armamentarium for carefully selected patients or an expensive and unnecessary technologic add-on to an operation that works well without it.