Sagittal Parameters of Spine-Pelvis-Hip Joints in Patients with Lumbar Spinal Stenosis

To explore sagittal compensation characteristics, including extra spinal-pelvic parameters and distal hip parameters, for analysis in middle-aged to the older patients with lumbar spinal stenosis (LSS) without spinal deformity and clarify the fitting relationship between the main sagittal parameters.

This retrospective single-center study included 205 patients with LSS in our department from January 2016 to December 2018, including 153 women (74.6%), with an average age of 67.6 ± 7.1 years. Sagittal parameters were obtained on the whole spinal lateral radiograph. Spinal parameters include thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), and lumbar lordosis (LL). Pelvic parameters include pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). Hip parameters include pelvic rotation (PR) and hip inclination angle (HIA). Spine-pelvic parameter is spino-sacral angle (SSA). Sagittal balance parameter is sagittal vertical axis (SVA). PI-LL, PT, SVA, HIA, and TLK were regarded as primary results, and the others were secondary outcomes. The independent sample t-test was used to compare gender. Pearson correlation analysis was used to evaluate the correlation between primary results and secondary results. We take PI-LL, PT, SVA, and TLK as dependent variables and include relevant factors for analysis.

In the case of gender, PI, PI-LL, and PT were found smaller in men than women, but TK is greater in men than women (27.3° ± 6.1° vs 23.3° ± 7.7°, p = 0.033). PI-LL was positively correlated with PT (r = 0.608, p < 0.001) and negatively correlated with HIA (r = -0.193, p = 0.010); PT was negatively correlated with HIA (r = -0.289, p < 0.01). As to the relationship between primary and secondary results, HIA was positively correlated with SS and PR (p < 0.01). SVA was positively correlated with SSA (r = 0.341, p = 0.010). The positive influencing factors and risk factors of SVA were SSA, and PI-LL played a negative regulatory role through proximal TK, the distal PT plays a positive regulatory role. The regulation of PI-LL was compensated through both TK and PT, with a fitting relationship of PI-LL = 0.5 × PT - 0.2 × TK.

There was a close interaction among spine-pelvic-hip sagittal parameters. We found the matching of PI-LL in the domestic middle-aged and elderly LSS population is regulated by thoracic spine and pelvis.