The analysis of spinopelvic parameters and stability following long fusions with S1, S2 or iliac fixation

Purpose: The purpose of this study was to analyse changes of spinopelvic parameters and stability in the treatment of degenerative lumbar deformity. Methods: A retrospective review was carried out on 70 cases of degenerative lumbar deformity treated by long fusion with uni-cortical S1 fixation alone (US1F group, n = 20), bi-cortical S1 fixation alone (BS1F group, n = 20), additional diagonal S2 fixation (DS2F group, n = 14), and additional iliac fixation (ILF group, n = 16) from July 2003 to April 2010. The sagittal vertical axis (SVA), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and stability were used to evaluate radiologic outcomes. The clinical outcome was evaluated using the Oswestry Disability Index (ODI). Results: In all groups, the LL was significantly increased at three months (p < 0.05). The PI and the SS of ILF patients significantly increased at three months (p < 0.05), while none of these values changed over time in non-ILF patients. The PT did not change postoperatively in any groups. The LL, SS, and PI were significantly greater in the ILF group at three months postoperatively and later (p < 0.05). DS2F and ILF had statistically significant stability compared to US1F and BS1F (p < 0.05). The ODI scores were significantly improved after surgery in all groups compared to before surgery (p < 0.05). Conclusions: Patients who had ILF in long fusion for the treatment of degenerative lumbar deformity had significant restoration of spinopelvic parameters compared to the other groups. In addition, DS2F and ILF provided more stability of distal instruments.