Prevalence and Clinical Impact of Coronal Malalignment Following Circumferential Minimally Invasive Surgery (CMIS) for Adult Spinal Deformity Correction.

Study design: Retrospective study.

Objectives: To determine prevalence and clinical importance of patients who had postoperative CM after CMIS for ASD correction.

Methods: We reviewed patients who underwent CMIS technique. Inclusion criteria were patients who were diagnosed with ASD, which is defined as having at least one of the following: coronal Cobb angle >20, SVA >50 mm, PI-LL >10, PT >20. They underwent >4 spinal levels fusion with CMIS technique and had at least 1-year follow-up. Preoperative and 1-year postoperative radiographs and clinical outcome measures (VAS, ODI, and SRS-22 scores) were used to make the comparisons.

Results: 120 patients were included. Radiographic outcomes, including CVA, coronal Cobb angle, LSF curve, SVA, LL, and PI-LL, and clinical outcomes, were significantly improved postoperatively in each of the 3 preoperative subgroups (Bao type A, B, and C). At 1-year post-operation, 10 patients (12.4 %) of type A turned out to be CM, 4 patients (21.1%) of type B, and 8 patients (40%) of type C remained CM. Comparing coronally aligned (CA) to coronally mal-aligned patients at 1-year follow-up in each coronal subtype revealed that clinical and radiographic outcomes were comparable.

Conclusions: CMIS technique significantly improves radiographic and clinical outcomes for ASD patients. Incidence rates of postoperative CM were similar to open surgery. Type C patients were at risk of postoperative CM than types A and B. However, most 1-year outcomes were not significantly different between postoperative CA and CM patients regardless of the preoperative coronal alignment characteristics except ODI scores in type A.