Duration of overlap during lumbar fusion does not predict outcomes

The relationship between degree of surgical overlap and adverse postoperative outcomes remains poorly defined. This study aims to evaluate the impact of increasing duration of overlap on lumbar fusion outcomes.

1302 adult patients undergoing overlapping surgery during single-level, posterior-only lumbar fusion at a multi-hospital, university health system were retrospectively assessed. Amount of overlap was calculated as a percentage of total overlap time. Patients were separated into groups with the most (top 10% of patients) and least amounts of overlap (bottom 40% of patients). Using Coarsened Exact Matching, patients with the most and least amounts of overlap were matched on demographics alone, then on both demographics and attending surgeon. Univariate analysis was performed for the whole population and both matched cohorts to compare amount of overlap to risk of adverse postsurgical events. Significance for all analyses was p-value < 0.05.

Duration of overlap was not associated with outcomes in the whole population, demographic-matched, or surgeon-matched analyses. Before exact matching, patients with the most amount of overlap had a significantly higher CCI score (p = 0.031) and shorter length of surgery (p = 0.006). In the demographic matched cohort, patients with increased overlap had a significantly shorter length of surgery (p = 0.001) only. In the surgeon matched cohort, there were no differences in length of surgery or CCI score.

Duration of surgical overlap does not predict adverse outcomes following lumbar fusion. These results suggest that overlapping surgery is a safe practice within this common neurosurgical indication.