The impact of COVID-19 on spine surgery: temporal trends in complications and patient-reported outcomes across a statewide cohort.

Background: The coronavirus disease 2019 (COVID-19) pandemic substantially disrupted spine surgery worldwide, with widespread deferral of elective procedures, shifts in patient selection, and reallocation of perioperative resources. Existing studies have produced conflicting findings on whether complication rates and patient-reported outcomes (PROs) worsened during the pandemic, and most are limited to single centers or short timeframes. The aim of this study was to evaluate the impact of the COVID-19 pandemic on patient characteristics, adverse events (AEs), and PROs following cervical and lumbar spine surgery across four prospectively defined pandemic phases in a statewide multicenter cohort. Methods: This retrospective cohort study used the Michigan Spine Surgery Improvement Collaborative (MSSIC) to analyze patients undergoing lumbar or cervical spine surgery during pre-COVID (January 2019-February 2020), onset-COVID (March 2020-September 2020), active-COVID (October 2020-February 2022), and post-COVID (March 2022-December 2022) phases. Patient demographics, surgical characteristics, 30- and 90-day AEs, and PROs were compared across cohorts using Chi-squared or Fisher's exact tests for categorical variables and analysis of variance (ANOVA) or Kruskal-Wallis tests for continuous variables. Results: Among 47,831 patients (33,532 lumbar; 14,299 cervical), demographics remained stable across phases. Lumbar onset-COVID patients had higher durotomy, urinary retention, and return-to-operating room (OR) rates, while cerebrospinal fluid (CSF) leak and 30-day readmissions declined during active-COVID. Cervical surgery showed increased dysphagia during active-COVID and higher return-to-OR and readmissions during onset and post-COVID, with cerebrovascular accident (CVA) and urinary retention rates decreasing over time. PROs were consistent, though lumbar patients more often achieved back pain minimal clinically important difference (MCID) during onset-COVID. Cervical patients reported higher 1-year satisfaction during onset, active, and post-COVID compared with pre-COVID. Functional recovery diverged: lumbar return-to-work fell at onset but stabilized, while cervical return-to-work stayed steady and improved post-COVID. Readmission causes shifted, with pulmonary complications rising initially then declining, while electrolyte, pharmacologic, and stroke-related etiologies decreased progressively. Conclusions: Spine surgery outcomes remained largely stable through the COVID-19 pandemic. Although certain complications temporarily increased during onset-COVID, outcomes normalized as systems adapted.