Abstract: BACKGROUND: Up to date, there is seldom research about the correlation between the harmonious alignment degree of lumbar lordosis and pelvic incidence and the improvement of postoperative clinical symptoms in patients with lumbar stenosis fusion. 
OBJECTIVE: To investigate the harmonious alignment degree of lumbar lordosis and pelvic incidence in patients with lumbar spinal stenosis and fusion, and compare the differences of spinal and pelvic sagittal parameters and clinical outcomes among different harmonious alignment degrees.
METHODS: The medical records of 110 patients with lumbar spinal stenosis (48 males and 62 females, aged 57±11 years) who were treated with posterior lumbar laminar decompression and internal fixation in the Department of Spinal Surgery, Tianjin Union Medical Center from December 2019 to December 2021 were retrospectively analyzed. The postoperative follow-up was more than 1 year. According to the harmonious alignment degree of lumbar lordosis and pelvic incidence, they were divided into two groups: Group A (n=47) (pelvic incidence-lumbar lordosis >10°) and group B (n=63) (pelvic incidence-lumbar lordosis ≤10°). The changes of clinical scores (low back pain visual analog scale score and Oswestry disability index) and spinal and pelvic sagittal parameters before and after surgery were compared between the two groups. The correlation between clinical symptom improvement and spinal and pelvic imaging parameters was analyzed.
RESULTS AND CONCLUSION: (1) There were no significant differences in preoperative pelvic sagittal parameters and clinical function between the two groups (P > 0.05). (2) There were no significant differences in operation time and blood loss between the two groups (P > 0.05). (3) At the last postoperative follow-up, the visual analog scale score and Oswestry disability index in group B were significantly improved compared with group A (P=0.000, P=0.005). Lumbar lordosis and sacral slope were also significantly improved (P=0.000, P < 0.05), and pelvic tilt was more significantly recovered (P=0.000). (4) Pearson correlation coefficient method results showed that the improvement of visual analog scale score of low back pain was significantly correlated with the improvement of pelvic tilt (r=0.209, P=0.008), lumbar lordosis (r=-0.133, P=0.021) and sacral slope (r=-0.156, P=0.031). Pelvic tilt was significantly correlated with Oswestry disability index (r=0.196, P=0.014). (5) It is concluded that reconstructed lumbar lordosis and reduced pelvic tilt for the harmonious alignment (pelvic incidence-lumbar lordosis ≤ 10°) can effectively improve the clinical symptoms of patients.

Key words: posterior lumbar fusion, lumbar spinal stenosis, sagittal alignment, lumbar lordosis, pelvic incidence