Prolonged Length of Stay and Risk of Unplanned 30-Day Readmission After Elective Spine Surgery: Propensity Score-Matched Analysis of 33,840 Patients

STUDY DESIGN Retrospective database study. OBJECTIVE To assess the association between prolonged length of hospital stay (pLOS) (≥4 d) and unplanned readmission in patients undergoing elective spine surgery by controlling the clinical and statistical confounders. SUMMARY OF BACKGROUND DATA pLOS has previously been cited as a risk factor for unplanned hospital readmission. This potentially modifiable risk factor has not been distinguished as an independent risk factor in a large-scale, multi-institutional, risk-adjusted study. METHODS Data were collected from the American College of Surgeons National Surgical Quality Improvement Program database. A retrospective propensity score-matched analysis was used to reduce baseline differences between the cohorts. Univariate and multivariate analyses were performed to assess the degree of association between pLOS and unplanned readmission. RESULTS From the 99,575 patients that fit the inclusion criteria, propensity score matching yielded 16,920 well-matched pairs (mean standard propensity score difference = 0.017). The overall 30-day unplanned readmission rate of these 33,840 patients was 5.5%. The mean length of stay was 2.0 ± 0.9 days and 6.0 ± 4.5 days (P ≤ 0.001) for the control and pLOS groups, respectively. In our univariate analysis, pLOS was associated with postoperative complications, especially medical complications (22.7% vs. 8.3%, P