Simple Moving Average: A Method of Reporting Evolving Complication Rates

Surgeons often cite published complication rates when discussing surgery with patients. However, these rates may not truly represent current results or an individual surgeon's experience with a given procedure. This study proposes a novel method to more accurately report current complication trends that may better represent the patient's potential experience: simple moving average. Reverse shoulder arthroplasty (RSA) is an increasingly popular and rapidly evolving procedure with highly variable reported complication rates. The authors used an RSA model to test and evaluate the usefulness of simple moving average. This study reviewed 297 consecutive RSA procedures performed by a single surgeon and noted complications in 50 patients (16.8%). Simple moving average for total complications as well as minor, major, acute, and chronic complications was then calculated using various lag intervals. These findings showed trends toward fewer total, major, and chronic complications over time, and these trends were represented best with a lag of 75 patients. Average follow-up within this lag was 26.2 months. Rates for total complications decreased from 17.3% to 8% at the most recent simple moving average. The authors' traditional complication rate with RSA (16.8%) is consistent with reported rates. However, the use of simple moving average shows that this complication rate decreased over time, with current trends (8%) markedly lower, giving the senior author a more accurate picture of his evolving complication trends with RSA. Compared with traditional methods, simple moving average can be used to better reflect current trends in complication rates associated with a surgical procedure and may better represent the patient's potential experience. [Orthopedics.2016; 39(5):e869-e876.].