Sagittal alignment in lumbar spinal canal stenosis

Objective: To evaluate the impact of lumbar canal stenosis on the sagittal balance of patients by studying the parameters of sagittal alignment. Methods: This single-centre prospective study, conducted from January 2020 to January 2022, included 47 patients presenting with lumbar canal stenosis confirmed by MRI and documented spinal balance assessed by full spine X-ray in standing profile. Patients with lumbo-radicular pain post-lumbar arthrodesis surgery were also included. The sagittal alignment parameters assessed were pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), L4-S1 lordosis (LL4-S1), PI-LL mismatch, thoracic kyphosis (TK), sagittal vertical axis (SVA), and TPA. Results: The mean pelvic incidence (PI) was 60.97° (SD 13.93°), with Class IV incidence in 36.2% of cases. Pelvic tilt (PT) averaged 18.65° (SD 10.91°), with values <10° in 19%, 10-25° in 53%, and >25° in 28% of patients. Sacral slope (SS) was 42.87° (SD 8.49°), with 53.2% in the 35-45° range. The measured lumbar lordosis (LL) was 46.10° (SD 17.84°), significantly lower than the theoretical LL (p=0.001). L4-S1 lordosis averaged 38.85° (SD 15.34°), also less than the theoretical value (p=0.017). PI-LL mismatch >10° was present in 60% of cases. Thoracic kyphosis (TK) averaged 14.57° (SD 11.29°), and sagittal vertical axis (SVA) was >5 cm in 81% of patients. T1 pelvic angle (TPA) was <20° in 57.4%. Conclusion: The analysis revealed that lumbar canal stenosis significantly affected spinal architecture, primarily through the loss of lumbar lordosis, and had a notable impact on thoracic kyphosis. Therapeutic approaches should not only focus on root decompression but also on restoring lumbar lordosis, with careful consideration of the arthrodesis level.