Temporal, Seasonal, and Monthly Effects on Total Knee Arthroplasty Surgical Site Infection Rates

Deep surgical site infections (dSSI) following total knee arthroplasty (TKA) are associated with morbidity and poor outcomes. Although numerous patient and non-patient factors have been correlated with dSSI development, the temporal and seasonal variability of dSSI is unclear. The purpose of this study was to investigate the monthly and seasonal variability of dSSI rates following TKA.

The dSSI database at a single large, urban, academic medical center was reviewed for TKAs performed between January 2009 and August 2018. The monthly and seasonal variability of dSSI was evaluated using a Poisson regression. Additionally, the change in dSSI rate was calculated over the entire study period.

We reviewed 15,230 consecutive TKAs. The average dSSI rate following TKA was 1.11% (SD: 0.91). The rate of dSSI decreased over the study period (r = 0.94, 95% CI: 0.85-1.05) but did not reach statistical significance. With summer as the reference season, there were no significant differences in the dSSI rate in fall, winter, or spring. With July as the reference season, there were no differences in the dSSI rate in any other months of the year.

Although non-significant, this analysis found a decreasing rate of dSSI after TKA over a nearly 10-year period. Interestingly, there was no difference in the dSSI rate following TKA in July as compared to other months or in summer as compared to other seasons. This conflicts with previous reports that have found an increased incidence of dSSI and other complications in July when the graduate medical education calendar begins.