When is staging complex adult spinal deformity advantageous? Identifying subsets of patients who benefit from staged interventions

OBJECTIVE The objective of this study was to identify baseline patient and surgical factors predictive of optimal outcomes in staged versus same-day combined-approach surgery. METHODS Adult spinal deformity (ASD) patients with baseline and perioperative (by 6 weeks) data were stratified based on single-stage (same-day) or multistage (staged) surgery, excluding planned multiple hospitalizations. Means comparison analyses were used to assess baseline demographic, radiographic, and surgical differences between cohorts. Backstep logistic regression and conditional inference tree analysis were used to identify variable thresholds associated with study-specific definitions of an optimal outcome in each cohort, defined as no intraoperative or surgery-related in-hospital adverse event. RESULTS There were 439 patients with complex ASD in the dataset (mean age 64.0 ± 9.3 years, 68% female, mean BMI 28.7 ± 5.5 kg/m²). Overall, 58.8% of patients were in the same-day group, while 41.2% were in the staged group. Demographically, cohorts were not significantly different (p > 0.05), but staged patients were more frail per total Edmonton Frail Scale score (p = 0.043). Staged patients also reported greater numeric rating scale scores for back pain than same-day patients (p = 0.002). Cohorts were comparable in magnitude of planned correction of C7–S1 sagittal vertical axis, pelvic incidence–lumbar lordosis (PI-LL) mismatch, and T4–12 kyphosis (all p > 0.05). Controlling for baseline age, frailty, and number of levels fused, staged patients reported significantly higher PROMIS Discretionary Social Activities scores by 6 weeks (p = 0.029). Radiographic outcomes by 6 weeks were comparable between cohorts, in terms of both magnitude of change from baseline and overall result (all p > 0.05). Same-day patients were significantly more likely to experience in-hospital complications (p = 0.013). When considering frailty thresholds for staging, only a Charlson Comorbidity Index ≤ 1.0 was associated with optimal outcome in same-day patients, while Edmonton Frail Scale score ≥ 7 (p = 0.036), ≥ 9 levels fused (p = 0.016), and baseline PI-LL mismatch ≥ 15.3° (p = 0.028) were associated with optimal outcome for staged patients. Yet, staging alone was not significantly associated with an optimal outcome perioperatively (p = 0.056). CONCLUSIONS While staged and same-day combined-approach surgeries yield comparable radiographic and patient-reported outcomes, certain subsets of complex ASD patients may benefit from staged surgery despite the invariably increased hospital length of stay. Individuals with increased frailty, moderate to severe PI-LL mismatch, and increased anticipated number of levels fused may experience a lower risk of perioperative adverse events if they undergo a staged procedure.