Introduction: Lumbar osteotomies are increasingly applied in the setting of adult sagittal spinal deformity and may be effective in obtaining appropriate spino‐pelvic re‐alignment. Additionally, it has been established that correction of global sagittal spinal balance improves self reported clinical outcomes. The study aims to investigate the impact of preoperative radiographic spino‐pelvic parameters on post‐operative sagittal vertical axis offset (SVA) with the hypothesis that patients with a larger pelvic tilt (PT) will require larger wedge resections
Methods: This is a multicenter consecutive retrospective review of 105 patients (mean age 54yo, 22M, 83F) who underwent lumbar PSO procedures for correction of major sagittal mal‐alignment (mean pre SVA=14.3cm). Pre‐ and post‐op free standing full length sagittal xrays were analyzed for regional curves (LL, TK), pelvic parameters (PI, PT) and global balance (SVA). Only patients with a pre‐op SVA ranging from 10 to 20cm and with a post‐op SVA less than 5cm were retained. The group was subdivided by pre‐op pelvic tilt (low/high, cutoff =35°). Independent t‐test analysis was used to determine differences in local/regional correction required to achieve the desired SVA correction
Results: A total of 14 patients were identified in the low_PT group and 16 in the high_PT group. There were no statistical differences in pre‐op SVA, thoracic kyphosis (TK) and post‐op SVA. The low_PT group had a significant lower lumbar lordosis (12° vs 31°, p=0.002) and a lower PT (23° vs 41°, p<0.001). Analysis of the surgical intervention demonstrated that high_PT group required a larger osteotomy resection (resp. 29° and 20°, p<0.001) and a larger regional change of lumbar lordosis (resp. +41° and+26°, p<0.001) to achieve an acceptable post‐op SVA (<5cm).
Conclusion: It has been accepted that improvements in surgical outcomes in patients with sagittal malalignment relates to global and pelvic radiographic parameters. An understanding of spino‐pelvic alignment may help the surgeon during complex re‐alignment procedures. This study demonstrates that in the presence of increased pelvic retroversion (high PT), a larger angular lumbar osteotomy and regional correction is required to obtain a satisfactory post‐operative SVA offset.