The time of year might influence the occurrence of surgical complications. Therefore, this study investigated correlations between the time-of-year and 30-day postoperative complication rates following primary total knee arthroplasty (TKA). Specifically, we determined (1) postoperative complication rates across all quarters; and (2) time-of-year influence on complications using univariate and multivariate regression analyses.
CPT code 27447 identified 147,473 TKAs from the NSQIP database. Readmissions, reoperations, as well as medical and surgical complications occurring within 30 postoperative days were assessed. All TKAs were divided into 4 cohorts based on the quarter-of-the-year (Q1-Q4) during which the surgery was performed. Chi-Square, ANOVA, linear regression, as well as univariate and multivariate analyses were performed to compare complication rates. A P < .05 was set for statistical significance.
Q3 had a higher risk of superficial infection when compared to Q1 (OR 1.37; 95% CI 1.12-1.69; P = .002). There was a lower risk of pneumonia between Q2 and Q1 (OR: 0.7; 95% CI 0.54-0.90; P = .007) as well as Q4 and Q1 (OR 0.76; 95% CI 0.6-0.96; P = .017). Blood transfusion was lower in Q2, Q3, and Q4 compared to Q1 (P = .02, P < .001, and P < .001).
This study provides a baseline analysis correlating the time of year and outcomes of TKA. However, since seasonality and weather can vary greatly in the United States by geographic region and time of year, future studies should be performed at a more granular level using hospital-specific data correlating weather and region to TKA outcomes.