Sunday, May 8, 2016

Do surgical results keep getting better with increasing experience?

Trend Toward High-Volume Hospitals and the Influence on Complications in Knee and Hip Arthroplasty

These authors used data from the National Inpatient Sample (2000 to 2012) to quantify trends in total hip arthroplasty (THA) and total knee arthroplasty (TKA) volume. They identified elective primary THAs and TKAs and grouped them by hospital by utilizing the hospital identifier, which indicated the geographic location of the hospital. They obtained county geographic and population data from the U.S. Census, and calculated the distances between hospitals and the centroids of counties. They obtained risk-standardized surgical complication rates for hospitals (2009 to 2012)  from Medicare Hospital Compare and grouped them by hospital volume.

They found a marked increase in the number of hospitals that performed a combined volume of ≥400 elective primary THAs and TKAs. The number of elective primary TKAs and THAs performed annually increased from 343,000 to 851,000.

In 2012, 65.5% of the arthroplasties were performed in high-volume hospitals (≥400 arthroplasties annually), and 26.6% of the arthroplasties were performed in very high-volume hospitals (≥1,000 procedures annually). The proportion of arthroplasties performed in low-volume hospitals (<100 arthroplasties annually) shrank from 17.9% to 5.4%. 

Very high-volume hospitals had the lowest complication rates (2.745 per 100; 95% confidence interval [CI], 2.56 to 2.93), and low-volume hospitals had the highest complication rates (3.610 per 100; 95% CI, 3.58 to 3.64; p < 0.0001) (odds ratio, 1.327; 95% CI, 1.26 to 1.40). Each successively higher hospital volume category manifested a lower complication rate.

Using 50 miles as a radius, the percentage of the U.S. population living near a high or very high-volume hospital was still 81.9%, well above the 65.5% of procedures performed at high-volume hospitals. Their data indicated that approximately 130,000 patients annually forwent an arthroplasty procedure at a high-volume hospital despite there being a high-volume center available in their geographic area. 

Comment: The relation between the quality of the result and surgical experience is an important topic - see this recent post (link). While this study is about hips and knees and hospital rather than surgeon volume, it is important because it suggests that the effect of volume may not have a 'threshold for an optimal result', in other words, there is no obvious level above which results stop improving. If a golfer that hits 200 balls per year is not as good as one who hits 500 per year who is not as good as one who hits 1000 per year, how much better are golfers who hit 2000 per year? The answer suggested by this study is that more (volume) is more (fewer complications).

The authors also pose the interesting question - what percent of patients are willing to drive 50 miles to lower their complication rate?  The observation 130,000 patients annually forwent an arthroplasty procedure at a high-volume hospital despite there being a high-volume center available in their geographic area may be due to patient unawareness of the data relating volume to complications, to their high degree of comfort with their local provider, or to the fact that for some, 50 miles of travel may remain a substantial barrier.

Our view is that patients need to ask about the experience of their surgeon in terms of volume, results and complications so that their decisions can be well informed.

Consultation for those who live a distance away from Seattle.

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