Overlap Before the Critical Step of Lumbar Fusion Does Not Lead to Increased Short-Term Morbidity

BACKGROUND: Few studies have assessed the impact of overlapping surgery during different timepoints of neurosurgical procedures. OBJECTIVE: To evaluate the impact of overlap before the critical portion of surgery on short-term patient outcomes following lumbar fusion. METHODS: In total, 3799 consecutive patients who underwent single-level, posterioronly lumbar fusion over 6 yr (2013-2019) at an academic hospital system were retrospectively studied. Outcomes included 30-d emergency department (ED) visit, readmission, reoperation, mortality, overall morbidity, and overall morbidity/surgical complications. Duration of overlap that occurred before the critical portion of surgery was calculated as a percentage of total beginning operative time. Univariate logistic regression was used to assess the impact of incremental 1% increases in the duration of overlap within the whole population and patients with beginning overlap. Subsequently, univariate analysis was used to compare exact matched patients with the least (bottom 40%) and most amounts of overlap (100% beginning overlap). Coarsened exact matching was used to match patients on key demographic factors, as well as attending surgeon. Significance was set at a P-value <.05. RESULTS: Increased duration of beginning overlap was associated with a decrease in 30-d ED visit (P = .03) within all patients with beginning overlap, but not within the whole population undergoing lumbar fusion. Duration of beginning overlap was not associated with any other short-term morbidity or mortality outcome in either the whole population or patients with beginning overlap. CONCLUSION: Increased duration of overlap before the critical step of surgery does not predict adverse short-term outcomes after single-level, posterior-only lumbar fusion.