Anterior Column Realignment (ACR) with and without Pre-ACR posterior release for fixed sagittal deformity

Background: Multiple studies have demonstrated a strong correlation between sagittal malalignment and healthrelated quality of life measures. Thus, correction of sagittal vertical axis (SVA), pelvic tilt (PT), lumbar lordosis-pelvic incidence (LL-PI), and T1 spinopelvic inclination (T1SPi) have become a primary objective of adult spinal deformity surgery. Anterior column realignment (ACR) has emerged as a less invasive technique and while the addition of posterior osteotomies has shown greater correction in ACR, it is unknown if a pre-ACR posterior release is necessary for optimal correction. The purpose of this study was to determine if pre-ACR posterior release allows for greater sagittal deformity correction. Methods: Seventeen patients were identified that underwent minimum 1-level ACR. Ten patients underwent an anterior-posterior surgical sequence without a pre-ACR posterior release, and 7 underwent a posterior-anteriorposterior (PAP) sequence with a pre-ACR posterior release. Radiographic outcomes at final follow-up and complications were compared. Results: Both groups saw significant improvements in LL, LL-PI, PT, SVA, and T1SPi but the correction was not significantly different between cohorts. With the exception of PT in the PAP group, the improvements in LL-PI, PT, and SVA correlated to improvement in Scoliosis Research Society-Schwab classification. The correction achieved at the ACR level, represented by motion segment angle, was greater in the PAP group by a degree that approached statistical significance. Five patients (29%) had 6 complications. Conclusions: Both techniques achieved meaningful improvements in overall sagittal alignment. Our results suggest that a pre-ACR posterior release may allow for greater correction specifically at the ACR level but may not always be necessary to achieve clinically meaningful correction of sagittal plane deformity. Level of Evidence: 3 Clinical Relevance: We present our experience with and without pre-ACR posterior release. To our knowledge, this is the first study to show that pre-ACR posterior release may achieve greater correction at the ACR level.