Spinopelvic Alignment by Different Surgical Methods in the Treatment of Degenerative Sagittal Imbalance of the Lumbar Spine

Study Design: A retrospective comparative study. Objective: To compare pedicle subtraction osteotomy (PSO) and iliac fixation (ILF) without osteotomy as methods of correcting lumbar spine deformities due to degenerative sagittal imbalance (DSI) through the evaluation of the changes in spinopelvic alignment. Summary of Background Data: Many papers have reported the surgical results after PSO and ILF for patients with fixed adult deformities. However, little is known about the difference between PSO and ILF corrections of spinopelvic alignment in adults with DSI. Methods: DSI patients who had undergone PSO or ILF with a minimum of 2-year follow-up (FU) were retrospectively studied in PSO (n = 30) or ILF (n = 25) groups. Lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA) were measured as spinal parameters and pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were used as measurements of pelvic parameters. Clinical outcomes were evaluated using a visual analogue scale (VAS) and Oswestry Disability Index (ODI) scores. Results: There were no statistically significant differences between the PSO and ILF groups with regard to age and fused segments, but there were significant differences in operative time and estimated blood loss. Concerning spinal parameters, there were significant increases of LL and TK in PSO group immediate postoperatively (LL: P = 0.014, TK: P = 0.017) and at the 2-year FU (LL: P = 0.021, TK: P = 0.022), but no significant difference in SVA was evident between the 2 groups. Within the pelvic parameters, there was a significant increase of SS and decrease of PT in the ILF group immediate postoperatively (SS: P = 0.013, PT: P = 0.009) and at the 2-year FU (SS: P = 0.024, PT: P = 0.027), but the PI in both groups was not changed after surgery and there was no significant difference between 2 groups. VAS and ODI were significantly improved after surgery in both groups. Conclusions: The PSO group was better than the ILF group in the correction of the LL and TK, but not with regard to the pelvic parameters. The ILF group was superior in the correction of the pelvic orientation as compared with the PSO group when the PI was constant after surgery. Ultimately, ILF effectively achieves better correction of the pelvic parameters (SS and PT).