CORR Insights®: What is the Association Between Hospital Volume and Complications After Revision Total Joint Arthroplasty: A Large-database Study

Where Are We Now?

Ricciardi and colleagues [11] performed a large-database study of 29,948 inpatient stays at New York hospitals to examine the relationship between revision total hip and knee arthroplasty volume and complications after surgery. The authors found that 90-day readmission rates were lower in the highest-volume centers compared to lower-volume hospitals, whereas reoperation rates within the first 90 days were not different when higher- and lower-volume settings were compared. Postoperative complication rates were higher among only the lowest-volume (quartile 1) institutions, and the authors found no association between 30-day mortality and hospital volume. These results suggest that regionalizing revision total joint arthroplasty (TJA) services away from the lowest-quartile hospitals may reduce 90-day readmissions and early complications rates.

Their study focuses on two important topics: (1) Volume-outcome relationships after revision TJA, and (2) the regionalization of revision arthroplasty services.

Regarding the correlation between hospital volume and outcomes, there are studies that find no correlation [2, 10], but another study found that adhering to standardized process of care measures can lead to improved quality of care independent of hospital or even surgeon volume [1].

High-volume hospitals have been associated with a lower risk of complications (and sometimes even of death after surgery) for a wide range of surgical procedures, and studies [4-6] about both primary and revision arthroplasty suggest that this applies to those operations as well. I note, though, one study evaluating implant survivorship found no relationship between that endpoint and higher hospital volume (though it did find that reconstructive survivorship was greater when the arthroplasty was performed by higher-volume surgeons) [2].

The other issue of interest here is the potential regionalization of revision TJA services based on hospital volumes, whereby patients might be referred to the highest-volume hospitals in the region. Regionalized primary TJA may reduce early readmissions and postoperative complications [3], but we lack sufficient evidence to advocate widespread implementation of regionalization of revision TJA. Ricciardi and colleagues [11] also point out a number of serious operational hurdles associated with this kind of regionalization.

Internationally, Jeschke and colleagues [5] in Germany and Glassou and colleagues [4] in a population-based study within the Nordic arthroplasty register association database made strong recommendations about regionalization to hospitals with higher volume TKA and THA patients (more than 50 patients per year) to reduce the overall revision and complication rates.

Where Do We Need To Go?

More than 1 million TJAs are performed each year in the United States. By 2030, the aging of the population would result in an estimated 11 million people with TJA (4 million THAs and 7.4 million TKAs) [12], making joint replacements one of the most common elective surgical procedures. At a cost of more than USD 30,000 per procedure, revision TJA consumes substantial healthcare resources [1] so there is a great (and growing) need to reduce the costs of this procedure. Considering that revision TJA is more complicated than a primary procedure, volume-based regionalization may be more appealing on the policy level compared to the regionalization of more-common primary procedures.

The large anticipated increase in revision TJAs must be addressed with effective planning of quality of healthcare services to make the procedure as safe, durable, and cost-effective as possible. Achieving these goals will require us to answer several fundamental questions:

1. Is hospital volume the main driving factor for quality? Hospital volume may not be the best standard to measure quality of care. Some population-based research suggests that prosthetic survivorship after THA was associated with surgeon volume, but not with hospital procedure volume [2].

2. What is the minimum acceptable volume, and at what volume thresholds do quality differences become observable? Unfortunately, the current definitions for high-volume hospitals are unreliable (as well as somewhat arbitrary), which is problematic if this is to be used as a quality metric [13]. We do not know if previous definitions of high-volume institutes are still accurate today, and there is the possibility that previous associations between procedure volume and outcomes are now quite different [8]. Traditional nonevidence-based quartile categories of hospitals have not captured the full extent of volume-related differences [7].

3. Since the association between volume of hospital procedures and complications and reoperations may vary depending on the healthcare system [2], can we extrapolate the current study’s results with different healthcare policies and surgeon-training systems?

4. Even if there is a correlation between volume of hospital revision TJAs and postoperative complications, reoperations, and 30-day mortality rates, what are the underlying causes of this correlation?

5. As Ricciardi and colleagues [11] noted, regionalization is complicated; for example, it can burden already-strained safety-net institutions, and pose unbearable (and unaffordable) travel demands on vulnerable rural populations. In light of that, we must ask what the implications might be of such a policy, and how we might balance the benefits of this approach against its costs and harms. The authors also found that hospitals in the mid-range of volume provided rates of short-term readmissions, complications, and mortality after TJA revision that were not different from the highest-volume institutions [11]. That being so, might it be more-efficient (and less burdensome) to use both mid- and high-volume hospitals if regionalization is considered?

How Do We Get There?

Nationwide population-based cohort studies, large-databased studies, and large-scale prospective studies with long-term followup can help us determine whether hospital volume is the right metric for healthcare quality. All-payer administrative datasets with patient’s demographic characteristics, physician’s information, well-audited operative databases, patients’ socioeconomic status, and hospital characteristics must be recorded to control for numerous covariates that are likely to confound the hospital volume-outcomes relationship. Future research must use more-objective hospital volume thresholds that include definitions for low, medium, and high-volume hospitals. Wilson and colleagues [13] support the use of stratum-specific likelihood ratio (SSLR) analysis, a way of examining receiver operating characteristic curves, to identify the volume thresholds where the risk of adverse outcomes after TKA drops most sharply. The next step is applying administrative database and SSLR analysis to similar administrative datasets in different geographical locations to define thresholds. However, Wilson and colleagues questioned whether this approach can be generalized and reproduced [13].

Regarding the correlation between hospital volume and outcomes after revision TJA, cross-sectional studies must clarify whether higher volume leads to better quality (practice-makes-perfect) or high-quality providers can attract more patients (selective-referral approach) [9]. To determine the causal effect of the hospital volume-outcomes relationship, researchers should develop regression models or simultaneous equation models with instrumental variables that include the number of potential patients, distance from patients’ homes to the hospital, population density, median patient income, and number of other area hospitals. By adding these variables, researchers can examine the effect of volume on outcomes after revision TJA.