Improvement in Sagittal Balance After Decompression Surgery without Fusion in Patients with Degenerative Lumbar Stenosis: Clinical and Radiographic Results at 1 Year

OBJECTIVE: To evaluate modifications in static spinal status after posterior decompression surgery without fusion in patients with symptomatic central canal stenosis. METHODS: From November 2014 to May 2016, 72 patients who underwent isolated decompression for lumbar spinal stenosis were enrolled prospectively in this single-center study. All of the patients had lateral full-body x-ray scans with the EOS system (EOS Imaging, Paris, France) before surgery and after 12 months of follow-up. Patients were classified into 3 groups according to their preoperative sagittal vertical axis (<50 mm, >= 50 mm, and <100 mm, >= 100 mm). RESULTS: SVA decreased significantly (SVA preoperative: 72.3 +/- 1 43.1, SVA postoperative: 48.3 +/- 46.8. P < 0.001). Lumbar lordosis increased significantly from 41.9 +/- 13.4 in the preoperative period to 46.5 +/- 14.8 at the last follow-up (P < 0.001). In the imbalance groups, the mean postoperative SVA decreased significantly compared with preoperative SVA (P = 0.004). Surgery led to a significant increase in lumbar lordosis in the 3 groups (P < 0.05). Nonetheless, a certain degree of residual imbalance persisted in the major imbalance group. In all of the groups, decompression surgery led to a significant improvement in clinical scores (P < 0.05). CONCLUSIONS: Our study showed an improvement in sagittal balance and lumbar lordosis after decompression surgery without fusion, even in patients with a preoperative SVA >100 ram. Howeverr a a ertain degree of sagittal imbalance may persist after surgery in patients with major initial imbalance (SVA >100 mm). Nonetheless, after surgery, these patients experienced a clinical benefit comparable with that in the other groups.