Adjacent Segment Reoperation and Other Perioperative Outcomes in Patients Who Underwent Anterior Lumbar Interbody Fusions at One and Two Levels.

OBJECTIVE: This is the first large retrospective analysis of patients undergoing anterior lumbar interbody fusion (ALIF) with concern for clinical determinants leading to reoperation for adjacent segment disease (ASD). The objective of this study is to examine the specific perioperative and clinical determinants that affect need for adjacent segment reoperation in patients who underwent 1-level and 2-level ALIF procedures for degenerative disc disorders. METHODS: All cases at our institution between 2008 and 2016 involving an ALIF performed for degenerative disc disorders at 1 or 2 levels were examined. A total of 404 ALIF cases, of which 268 were single-level (66.33%) and 136 were 2-level procedures (33.67%), were included. Adjacent segment reoperation was the primary outcome. Secondary outcomes included increased blood loss, extended surgery duration, greater nonhome discharge, extended hospitalization, and higher total direct costs. Univariate and multivariate logistic regression assessed how number of levels fused related to perioperative outcomes. RESULTS: The patient cohorts shared similar demographic characteristics and showed expected differences in certain intraoperative outcomes. After controlling for preoperative and intraoperative variables, multivariate regression showed that patients who underwent 2-level ALIFs experienced increased odds of adjacent segment reoperation (P = 0.0424) but no other adverse clinical outcomes. CONCLUSIONS: Our findings support a biomechanical hypothesis of ASD onset after fusion, suggesting that the risk of ASD after ALIF lies primarily in the number of levels fused rather than any demographic or intraoperative variables.