Risk Factors for Pelvic Non-responders Even after Pelvic Incidence-Lumbar Lordosis Overcorrection and Their Impact on Surgical Outcomes

Study DesignRetrospective observation study.ObjectivesDespite pelvic incidence (PI)-lumbar lordosis (LL) overcorrection, some patients exhibit residual pelvic tilt (PT) malalignment, termed pelvic non-responders (PNRs). We aimed to identify risk factors for PNRS after PI-LL overcorrection and its impact on surgical outcomes.MethodsA retrospective analysis of 181 adult spinal deformity (ASD) patients who underwent fusion of ≥ five levels. PNRs were defined as postoperative PT ≥ 20° despite PI-LL overcorrection. Patient-reported outcomes (PROMs) and mechanical complications, such as proximal junctional failure (PJF), were documented. Logistic regression identified significant risk factors for PNRs.ResultsAmong the 181 patients, 30 (16.6%) were classified as having PNRs. Preoperative PI and postoperative PI-LL mismatch were significantly higher in PNRs than in PRs. Multivariate analysis identified higher preoperative PI, postoperative PI-LL ≥ -2°, lordosis distribution index (LDI) < 53%, and increased postoperative thoracic kyphosis as significant risk factors for pelvic non-response. PJF was significantly higher in PNRs (30.0% vs 10.6%, <i>P</i> < 0.01). At 1 year postoperatively, PNRs had lower SRS-22 scores in activity, pain, appearance, and mental health (<i>P</i> < 0.05), but MCID analysis indicated these differences may not be clinically meaningful.ConclusionsLarger preoperative PI, lower postoperative LDI, and higher postoperative PI-LL are significant risk factors for pelvic non-response in ASD patients with PI-LL overcorrection. PNRs are at increased risk of higher rates of PJF. Surgical strategies should prioritize achieving the target PI-LL and an LDI of ≥53% to optimize alignment and reduce the risk of PNRs and associated mechanical complications.