Introduction:

Recent studies investigating seasonality as a risk factor for surgical site infections (SSI) after spine surgery show mixed results. This study utilizes national data to analyze seasonal effects on spine surgery SSIs.

Methods:

NSQIP data (2011-2018) was queried for posterior cervical fusions (PCF), cervical laminoplasties, posterior lumbar fusions (PLF), lumbar laminectomies, and deformity surgeries. Patients aged >89 and procedures for tumors, fractures, infections, and non-elective indications were excluded. Patients were divided into warm (admitted April-September) and cold (October-March) seasons. Demographics were compared using univariate analysis. Endpoints of SSI and reoperations for wound debridement/drainage were compared using multivariable logistic regression. Stratified analyses were performed by surgery type and pre- vs. post-discharge infections.

Results:

Overall (N=208,291) SSI was more likely in the warm season (OR=1.15, 95%CI=1.08-1.23, p<0.0001), as well as for PCF (OR=1.40, 95%CI=1.08-1.80, p=0.011), PLF (OR=1.15, 95%CI=1.04-1.28, p=0.006), and lumbar laminectomies (OR=1.13, 95%CI=1.03-1.25, p=0.014). Post-discharge infections were also more likely in the warm season overall (OR=1.15, 95%CI=1.07-1.23, p<0.0001), and for PCF (OR=1.32, 95%CI=1.01-1.73, p=0.041), PLF (OR=1.14, 95%CI=1.03-1.27, p=0.014), and lumbar laminectomies (OR=1.15, 95%CI=1.04-1.27, p=0.007). In-hospital infections were more likely during the warm season only for PCF (OR=2.54, 95%CI=1.06-6.10, p=0.037). Reoperations for infection were more likely during the warm season for PLF (OR=1.29, 95%CI=1.08-1.54, p=0.005).

Conclusion:

PCF, PLF, and lumbar laminectomy during the warm season had significantly higher odds of SSI, especially post-discharge. Reoperation rates for wound management were significantly elevated during the warm season for PLF. Identifying seasonal causes merits further investigation and may influence surgeon scheduling and expectations.