STUDY DESIGN: Cohort study.

OBJECTIVE: To report outcome after primary surgery for Adult Spinal Deformity (ASD), and assess risk factors for extended length of stay (extLOS) and increased 90-day readmission.

SUMMARY OF BACKGROUND DATA: Complications after ASD surgery have been reported in 20-50% of patients. Few studies have focused on detailed information concerning postoperative morbidity.

METHODS: Patients >18 years undergoing primary instrumented surgery for ASD in Denmark in the period 2006-2016 were included. Patients were identified in the Danish National Patient Registry (DNPR) using procedure codes for instrumented spine surgery combined with diagnosis of spinal deformity. Information on length of stay (LOS), readmissions, and mortality were retrieved from the DNPR. Medical records were reviewed for causes of extLOS (LOS >10 days) and readmission within 90 days after surgery. Charlson Comorbidity Index (CCI) was calculated for all patients based on DNPR.

RESULTS: We included 892 patients. Median LOS was 8 days (interquartile range (IQR) 7 - 11). A total of, 175 (28.0%) patients had extLOS; 75% due to "medically" related complications. Most common medically related reason (>50%) for extLOS was pain/mobilization difficulties. The 90-days readmission risk was 13.8%; 73.2% of readmissions were "medically" related, primarily opioid related side effects (18.2%) and pain/mobilization issues (15.2%); 31.8% of readmissions were "surgically" related and 16.7% of patients required revision surgery. 90-days mortality was 0.9%. Age groups 61-70 years, >70 years, CCI score 1-2 and CCI score ≥3 were associated with increased risk of extLOS (Odds Ratio (OR) = 1.79, 2.01, 1.81 and 2.49 respectively). Age group >70 years and CCI score 1-2 were associated with increased risk of readmission (OR = 2.21 and 1.83).

CONCLUSIONS: Increasing age and comorbidity were associated with increased risk extLOS and readmission. Pain/mobilization difficulties were the most common postoperative complications. A future focus on early mobilization and pain management may improve outcome of ASD patients.

LEVEL OF EVIDENCE: 3.