Compensation Characteristics of Spinal Sagittal Malalignment According to Pelvic Incidence in Elderly Patients with Degenerative Lumbar Spinal Stenosis

Objective Compensation characteristics of spinal sagittal malalignment according to pelvic incidence (PI) have yet to be elucidated. This study aimed to investigate the difference in compensatory segments according to PI in elderly patients with degenerative lumbar spinal stenosis (DLSS). Methods This retrospective study included 196 patients (143 females, 53 males) suffering from DLSS with an average age of 66.73 years in our department. Sagittal parameters were obtained on the whole spinal lateral radiograph, including T1‐T12 slope (T1S‐T12S), Cobb angle (CA) of the functional units of the thoracic spine, thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), PI, the ratio of PT to PI (PT/PI), PI minus LL mismatch (PI‐LL), sagittal vertical axis (SVA). Patients were divided into the low and high PI groups according to the median value of PI. With reference to the value of SVA and PI‐LL, each PI group was further grouped into the balance subgroup (SVA 10°), and imbalance subgroup (SVA ≥50 mm). Independent samples t‐test/Mann–Whitney U test, one‐way ANOVA/Kruskal‐Wallis test, and Person correlation analysis were utilized for statistical test. Results The median value of PI was 47.65°. 96 and 100 patients were assigned to low and high PI groups, respectively. Correlation analysis indicated that the T8‐T12 slope and T10‐T12 slope were associated with PI‐LL in the high and low PI groups, respectively (all, p