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 ± 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 mm. However, a certain 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.