Do adult spinal deformity patients who achieve and maintain PI-LL < 10 have better patient-reported and clinical outcomes compared to patients with PI-LL 10? A propensity score-matched analysis

Purpose To investigate whether patients with spinopelvic mismatch (PI-LL >= 10) report worse patient-reported outcomes (PROs) compared to patients who achieve PI-LL < 10 at 2-year postop.Methods In this retrospective study, propensity score matching (PSM) was used to analyze patients who underwent posterior spinal fusion due to deformity, as defined by one or more of the following criteria: PI-LL >= 25 degrees, T1 pelvic angle >= 30 degrees, sagittal vertical axis >= 15 cm, thoracic scoliosis >= 70 degrees, thoracolumbar scoliosis >= 50 degrees, coronal malalignment >= 7 cm, or those who underwent a three-column osteotomy or fusion with >= 12 levels. Key outcomes were total Scoliosis Research Society-22r, Oswestry Disability Index (PROs), and reoperation at 1- and 2-year postop. Patients were dichotomized based on their 2-year alignment: PI-LL >= 10 degrees and PI-LL < 10 degrees. A multivariable logistic regression model identified factors associated with achieving PI-LL < 10 degrees, and independent predictors were matched using propensity score matching. Binary outcomes within matched cohorts were analyzed using the McNemar test, while continuous outcomes were analyzed using the Wilcoxon rank-sum test.Results One hundred sixty-four patients with 2-year follow-up were included; mean age was 50.5 (standard error mean (SEM): 1.4) years, body mass index was 24.1(SEM 1.0), and number of operative levels was 13.5 (SEM 0.3). 84 (51.2%) and 80 (48.8%) patients achieved PI-LL < 10 and PI-LL >= 10 at 2-year follow-up, respectively. Baseline pelvic incidence [odds ratio (OR): 0.96 (95% CI 0.92-0.99)] and baseline PI-LL [OR: 0.95 (95% CI 0.9-0.99)] were independent predictors of achieving PI-LL < 10 at 2 years. When comparing propensity matched pairs, no significant differences were found in baseline PROs. At both 1- and 2-year follow-up, outcomes on the SRS-22r scale were nearly identical for both groups (function [4.1(0.1) vs 4.0 (0.1), P = 0.75] ,Pain [3.9 (0.2) vs 3.9 (0.2), P = 0.86], appearance [4.2 (0.2) vs 3.8 (0.2), P = 0.08], mental health [4.1 (0.2) vs 4.1 (0.1), P = 0.96], satisfaction [4.4 (0.2) vs 4.4 (0.2), P = 0.72], and total [90.2 (2.5) vs 88.1 (2.5), P = 0.57]). Additionally, ODI scores at 2 years were comparable [18.1 (2.9) vs 22.4 (2.9), P = 0.30]. The 90-day reoperation rate was 2.6% (one patient) in both matched cohorts (P > 0.99). There was no significant difference in 1-year (P > 0.9999) or 2-year (P = 0.2207) reoperation rates between the groups.Conclusion Patients who achieve and maintain PI-LL < 10 2-years postop following adult spinal deformity surgery have nearly identical SRS-22r and ODI outcomes, and comparable 2-year reoperation rates as compared to patients who have PI-LL >= 10.