Study Design. Retrospective analysis of prospectively collected database. Objective. Adult spinal deformity (ASD) has increasingly been treated with minimally invasive surgical (MIS) techniques. The authors sought to identify factors associated with delayed deterioration of ODI between 1 and 2 years postoperatively following minimally invasive surgery (MIS) for adult spinal deformity (ASD). Summary of Background Data. Coronal malalignment is known to be associated with patient disability but the extent to which coronal alignment is associated with delayed deterioration after circumferential MIS surgery for ASD is unknown. Methods. A retrospective analysis of prospectively collected data from the Minimally Invasive Surgery International Spine Study Group (MIS-ISSG) was conducted, including 67 patients who underwent circumferential MIS for ASD with one and two-year follow-ups. The patient cohort was dichotomized by identifying patients who reported higher ODI scores at 2 years than 1 year (somewhat improved) and compared with patients who reported stable or improved ODI over the same time course (very improved). Preoperative and postoperative factors influencing ODI changes were analyzed, focusing on radiographic outcomes and complications. Results. Of the 67 patients, 31 reported an increase in ODI at two years compared with one year but these patients continued to show an improvement in ODI compared to preoperative baseline. Statistical analyses revealed no significant differences in baseline demographic, surgical, or preoperative characteristics between the “somewhat improved” (2-year ODI>1-year ODI) and “very improved” (2 y ODI≤1 y ODI) cohorts ( P >0.05). However, the somewhat improved group had a significantly higher mean central sacral vertical line (CSVL) at all follow-up intervals (6-week CSVL mean 36.26 mm in the Somewhat improved group versus 22.8 mm in the very improved group, P =0.01). Conclusion. Early post-operative coronal malalignment is associated with delayed changes in functional outcomes following MIS for ASD.
Chan et al. (Thu,) studied this question.