Association of Spino-Pelvic Sagittal Parameters with Pain and Disability Outcomes Following Lumbar Fusion: A Prospective Cohort Study

Purpose: Sagittal alignment restoration is considered crucial for successful lumbar fusion outcomes, yet the specific relationships between spino-pelvic parameters and patient-reported outcomes remain incompletely understood. This prospective cohort study investigated associations between sagittal alignment parameters and pain/disability outcomes following lumbar fusion surgery. Methods: Sixty-four consecutive patients with degenerative lumbar disc disease undergoing fusion surgery were prospectively enrolled. Radiographic parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA) were measured pre- and post-operatively. Visual analog scale (VAS) for pain and Oswestry Disability Index (ODI) were assessed pre-operatively and at final follow-up (median 99.5 days). Correlational analyses examined relationships between sagittal parameters, parameter changes, and clinical outcomes. Results: Despite significant clinical improvement (median ODI: 73 to 16, p<0.001; mean VAS: 9.02 to 2.81, p<0.001), average lumbar lordosis paradoxically decreased by 6.61° whilst SVA increased by 14.4mm. However, the magnitude of change in sagittal parameters strongly predicted outcomes. Greater lordosis restoration correlated with improved pain (r=0.420, p=0.001) and disability (r=0.252, p=0.046). SVA reduction correlated with pain improvement (r=-0.380, p=0.002). Absolute postoperative alignment values showed no significant associations with outcomes. Conclusions: Dynamic sagittal correction—rather than achieving normative alignment targets—predicts early clinical success following lumbar fusion. These findings support individualised surgical planning focused on maximising patient-specific realignment rather than pursuing universal radiographic goals.