Impact of the hip osteoarthritis on sagittal spine-pelvis alignment parameters in lumbar spinal stenosis with sagittal malalignment: a propensity score matching study.

Purpose: There is a paucity of data regarding the sagittal spine-pelvis-leg alignment and the compensatory mechanisms in patients with lumbar spinal stenosis (LSS) and hip osteoarthritis (HOA). In this study, we aim to evaluate the association of HOA with sagittal spine-pelvis alignment parameters in a population of patients with lumbar spinal stenosis and sagittal malalignment.

Methods: We retrospectively analyzed a cohort of prospectively enrolled patients with degenerative LSS and sagittal malalignment between January 2019 and December 2023. Radiographic parameters evaluated were pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), PI-LL, sagittal vertical axis (SVA), T1-pelvic angle (T1PA), sacrofemoral angle (SFA), pelvic obliquity (PO), and femoral inclination (FI). HOA was graded by Kellgren-Lawrence (K/L) grades and divided into low-grade HOA (LOA; grade 0-2) and severe HOA (SOA; grade 3 or 4) groups. LOA group patients were propensity-score matched (PSM) 1:1 to SOA group patients based on age and PI. Univariate, multivariate, and subgroup analyses were used to analyze the association between HOA and sagittal malalignment.

Results: Out of 379 patients, 116 with LOA and 116 with SOA were analyzed after propensity score matching for age and PI. SOA patients exhibited significantly lower FPA (184.01 ± 9.97 vs 186.78 ± 10.11, p = 0.036), higher SS (33.05 ± 9.38 vs. 30.51 ± 9.47, p = 0.042), and lower PT (16.28 ± 8.67 vs. 18.53 ± 7.84, p = 0.040) compared to the LOA group. Subgroup analysis revealed that SOA patients with a SVA > 4 cm had significantly higher PI (51.49 ± 11.64 vs. 47.83 ± 10.73, p = 0.025) and PT (18.71 ± 8.76 vs. 14.67 ± 8.56, p < 0.001), which were not observed in the LOA group. Multivariable linear regression analysis revealed that a greater Kellgren-Lawrence (K/L) Grade was significantly associated with a higher SVA after adjusting for age, BMI, and PI.

Conclusion: In this PSM study, patients with SOA exhibit reduced pelvic tilt and hip extension in standing positions compared to those with LOA. Additionally, the SOA patients had worse global sagittal alignment than their LOA counterparts.