CORR Insights^®: Risk Factors for Revision Within 10 Years of Total Knee Arthroplasty

Where Are We Now?

Revision TKA is a challenge to all involved parties. It is a technically demanding procedure to surgeons, an intervention with a real risk of complications to patients, and a financial burden to societies. For the past several decades, enormous efforts have been made to reduce the frequency of this difficult clinical challenge. Despite these efforts, the number of revision TKAs has continued to increase [3, 4, 7, 9], and is expected to grow in the coming decades as the number of primary TKAs continues to increase [5]. A comprehensive understanding of risk factors for failure of primary TKAs would be critical to our efforts to minimize the revision burden.

Identifying risk factors is much more challenging than it seems. First, each kind of failure —infection, loosening, wear, instability, stiffness, and patella-related complications — has its own risk factors, so any database must contain sufficient numbers of patients to allow analysis of each major failure mechanism separately. Likewise, hospital and community factors must be considered, as these, too, are important. Administrative databases, which are typically much larger than a single institute’s series, may serve as a useful resource in identifying risk factors for TKA failures. In the past, investigators have used this type of administrative data to identify pertinent risk factors for TKA failure [1, 2, 6, 8]. A recent study [1] using 117,903 Medicare patients who underwent primary TKA between 1998 and 2010, found that several comorbid conditions such as chronic pulmonary disease and depression were associated with early revision within 12 months. Another recent study [2] involving 61,767 TKA patients, also from a Medicare database, found that younger male patients with higher comorbidities and low socioeconomic status were at increased risk for TKA failures.

Where Do We Need to Go?

In the study by Dy and colleagues, the authors determined the frequency and reasons for revision TKA within 10 years of primary TKA, and identified relevant patient, community, and hospital factors. Dy and colleagues analyzed two statewide databases consisting of 301,955 patients from New York and California. The researchers used identifier codes to determine whether patients underwent revision within 10 years of TKA. Dy et al. analyzed patient, community, and hospital characteristics using multivariate regression to identify predictors for revision TKA. Results of the study showed a revision rate of 4% at 5 years, and 9% at 9 years, with aseptic failure (67%) considered the most common reason for revision, followed by septic failure (27%). The authors found the strongest predictors for revision were younger age, male sex, black race, and lower hospital volume. They also found modest predictors for revision, including the presence of comorbidity (coagulopathy, chronic obstructive pulmonary disease, depression, and diabetes), insurance type (private insurance), education (most educated), and poverty levels (most impoverished) of a community.

The size of this study (more than 300,000 primary TKAs) and its geographic locations (New York and California) make it more generalizable than results drawn from single-center series or similar studies using a smaller administrative database from a single state or single payer. As the authors noted, these findings would be suitable for patient counseling particularly in the United States.

Despite its benefits, this study is not free from the limitations of relying on an administrative database. No detailed information is available for failure mechanisms, and the identified risk factors are not specific to a failure-mechanism. Community information was based on the area zip code, which excludes the possibility of evaluating the association of individual income and education level with TKA failures. Furthermore, the authors arbitrarily designated a time-period of 10 years as the cutoff in order to increase power to analyze multiple variables. It is likely that the collective use of all failures within 10 years resulted in combined analysis of two typical schematic classifications — early and late failures. Therefore, it is not possible to understand how the identified risk factors are differentially associated with early and late failures. Nonetheless, this study substantiates our sense that failures of primary TKAs are the result of multiple related factors including patient, hospital, and community factors, so efforts to reduce revision TKA must occur on all those fronts in order to achieve best effect.

How Do We Get There?

Accurate and comprehensive knowledge of risk factors for TKA failures is of paramount importance to develop optimal strategies to lower the number of revision TKAs. Studies based on administrative data should be continued in order to provide the big picture, which is extremely valuable, but researchers should be cautious not to simply take the information at face value. They should also seek support from all available sources of different types: original studies from cohorts, meta-analysis data, and statewide or nationwide joint registry data. More specifically, we need further research to provide a detailed association of the identified risk factors with each individual reason for failure. Additionally, contemporary data should be used to provide caregivers with timely relevant information.

The ultimate goal of healthcare providers involved in revision TKA is to develop effective preventive measures. Comprehensive and multidisciplinary strategies should be established to optimize preoperative health status, improve coordination of care, maximize hospital efficiency, and assure optimal implant surveillance in high-risk patients.