CORR Insights®: What Are the Indications for Implant Revision in Three-component Total Ankle Arthroplasty?

Where Are We Now?

Total ankle arthroplasty (TAA) has seen a dramatic increase in use during the past 20 years [2, 6, 9, 10]. A review of the Nationwide Inpatient Sample found that between 2000 and 2010, ankle arthrodesis was still used six times more often than TAA [10]. A separate review that included the subsequent 2 years of the Nationwide Inpatient Sample data sample, however, captured the steep trajectory in TAA use [2]. The percentage of patients receiving TAA to treat end-stage ankle arthritis grew from 17.6% in 2007 to 51.5% in 2012. This increase in TAA use has coincided with an expanding catalog of available implants. Since 2004, the number of FDA-approved TAA systems routinely used in the United States has grown from one to more than 10.

The inevitable consequence of the expanded use of TAA is an increase in the number of revisions. The data regarding the success of primary TAA are limited by a lack of standardization, but two recent meta-analyses reported survivorship rates of 88.5% at 9 years [8] and 74% at 10 years [13]. In the past, surgeons typically salvaged loose or infected TAAs by converting them to ankle or tibiotalocalcaneal arthrodeses. Because of improvements in implants and surgical techniques, however, the indications for revision arthroplasty have expanded. A review of studies published between 2008 and 2018 found that of the 249 TAA implants that were removed, more than 80% were salvaged with revision arthroplasty [8]. Yet, even as our ability to perform revision TAA improves, early identification of patients who are most likely to eventually undergo a salvage procedure may allow for earlier, lesser interventions that could delay or prevent surgery. The efficiency of routine annual clinical and radiographic monitoring of clinically stable patients after THA and THA has been questioned. As few as 9% of routine follow-up visits after THA and TKA result in a change in patient treatment [3]. Further, only 15.3% of the complications resulting in a reoperation after THA and TKA were identified at routine postoperative follow-up visits, and there were approximately 1000 routine follow-up visits for every complication identified [11]. Extrapolation of these data to the growing population of patients undergoing TAA strongly suggests that routine annual monitoring after TAA consumes a substantial amount of healthcare resources for little apparent return.

Richter et al. [12] have worked to provide a step on the path toward addressing these issues. They retrospectively evaluated more than 1000 primary TAA procedures performed by, or under the supervision of, a single surgeon and using a single three-component ankle prosthesis. Interestingly, in their categorization of the factors resulting in revision of TAAs, half were issues that existed before or during the primary surgery (instability, pain from another cause, or technical error) and half were issues that developed at some point after surgery (deep infection, aseptic loosening, or cyst formation). These findings reinforce our need to better understand the factors and interventions that affect the longevity of TAA at every stage.

Where Do We Need To Go?

To provide the best care for patients who undergo TAA, we need tools to predict, as accurately as possible, each patient’s risk of implant revision. Preoperatively, these tools could help identify patients for whom TAA might not be indicated, determine whether a particular patient might benefit from specific implant characteristics (such as a stemmed tibial component), and evaluate the timing of, and indication for, adjunct procedures such as gastrocnemius recession, ligament reconstruction, or correction of a foot deformity. In addition, we could use these tools to refine our surgical techniques and intraoperative decision-making to maximize survivorship of the implant. For instance, we might determine how much foot correction can be done at the time of the primary TAA and when such a correction should be staged. Finally, postoperatively, these tools could help us to better counsel patients regarding expectations and activity recommendations, and perhaps determine an appropriate monitoring schedule to evaluate for radiographic signs of progressive instability, worsening foot deformity, or cyst formation that might be addressed in order to delay or prevent implant removal. Overall, by better understanding and predicting the indications for implant revision, we could identify ways to mitigate that risk and prolong the life of the primary TAA implant.

For a predictive tool of this type to achieve maximum utility, it needs to be broadly applicable. For understandable logistical reasons, much of the research concerning revision of primary TAA is limited to reports on a single implant or by a small number of expert surgeons, or from a single, high-volume center. In addition, the data collection in the existing studies generally has not been standardized, making comparison among studies problematic. Even the description of complications after TAA is so varied that a review of 117 published articles found that 55.9% of the 572 unique terms used to describe adverse events appeared in just a single study [7]. These limitations make it exceedingly difficult to use existing studies to evaluate the risk of implant revision in a way that is broadly applicable to the patient sitting across from us in clinic.

How Do We Get There?

Developing broadly applicable tools will require an extensive amount of prospectively collected data. Data collection on this scale is best done through a national registry database. Although existing surgical databases in the United States, including the American College of Surgeons National Surgery Quality Improvement Program and the National Inpatient Sample, have been queried for available information on TAA [5], they have substantial limitations to their datasets, both in the number of patients they do not capture and the limited, non-standardized scope of data collected. Several countries outside the United States have established national joint replacement registries, including the ankle-specific Swedish Ankle Registry. Unfortunately, studies based on these registries have also been limited by heterogeneous data [1].

The ability of a national registry database to provide the best possible data for developing a broadly applicable predictive tool will depend on two important factors. First, the data to be collected must be standardized. This foreboding project will most likely need to be a collaboration between national organizations, such as the American Orthopaedic Foot and Ankle Society’s Committee on Health Outcomes, Registries, and Data, and leading surgeons in the field. The Committee on Health Outcomes, Registries, and Data, a relatively new committee in the American Orthopaedic Foot and Ankle Society, is expanding on lessons and techniques learned from the Orthopaedic Foot and Ankle Outcomes Research Network initiative of the American Orthopaedic Foot and Ankle Society, which established an internet-based platform to collect standardized, prospective data from multiple centers. Obtaining a balance between collecting an adequate amount of data and minimizing the additional burden for patients and providers will be the primary challenge. The second, equally necessary factor is the broad participation of practicing surgeons who perform TAA. Even with perfectly standardized data collection, the utility of a registry depends on participating surgeons to provide their data. Admittedly, the administrative burden of modern medicine is already heavy, but if we can commit ourselves to participating in this type of ambitious project, we may be rewarded with a predictive tool to help us provide the best possible care for patients who undergo TAA.

The development of a clinically useful predictive tool for maximizing the survivorship of TAA will, without question, be a challenge. As standardized data are collected, revision procedures will need to be analyzed and work will need to be done to determine the combination of factors that might have resulted in a revision procedure. Patients with longer survivorship will also need to be reviewed to determine what factors contributed to that longevity. Ideally, the relative contribution of preoperative, intraoperative, and postoperative factors to the risk of revision of primary TAA can be determined so that for an individual patient, appropriate decisions can be made at each stage. A recent article in Clinical Orthopaedics and Related Research® thoughtfully discussed the skeptical evaluation of such predictive models and the likelihood they will play an increasing role in the decision-making of the future [4].