Restoration of Sagittal Alignment as a Key Factor in Degenerative Spine Surgery: A Comparative Analysis of Outcomes in Postoperative Balanced and Imbalanced Cases

Introduction The current consensus for treating sagittal imbalance in degenerative spine disease supports deformity correction. However, there is a growing trend toward limited fusion, particularly in patients presenting predominantly with leg symptoms. The present study aimed to compare radiological and clinical outcomes following lumbar fusion between patients with postoperative sagittal balance and those with residual imbalance. Methods This study included 270 patients who underwent limited lumbar arthrodesis and were followed for two years. Radiological parameters-sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS)-were recorded preoperatively and at the final follow-up. Clinical outcomes were assessed using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and Short Form-36 (SF-36). Patients were divided into two groups based on postoperative sagittal alignment: balanced (SVA < 50 mm) and imbalanced (SVA > 50 mm). Both intragroup pre- and postoperative improvements and intergroup differences in outcomes were analyzed. Results Out of 270 patients, 194 had good sagittal alignment and 76 had sagittal imbalance (SVA > 50 mm). Both groups showed significant postoperative (two-year follow-up) improvement in quality-of-life scores (VAS, ODI, and SF-36) compared with baseline values (p < 0.001). However, when comparing the degree of improvement between the balanced and imbalanced groups, no statistically significant differences were observed. A significant but weak negative correlation was noted between the change in the VAS score and the socioeconomic status in patients with sagittal imbalance of the spine. Conclusion In appropriately selected patients, limited lumbar fusion can achieve favorable short-term outcomes irrespective of postoperative sagittal alignment. These findings suggest that extensive deformity correction may not always be necessary in degenerative cases presenting primarily with leg symptoms.