Be Prepared: Preoperative Coronal Malalignment Often Leads to More Extensive Surgery Than Sagittal Malalignment During Adult Spinal Deformity Surgery

OBJECTIVE: To evaluate the effect of coronal alignment on: (1) surgical invasiveness and operative complexity and (2) postoperative complications. METHODS: A retrospective, cohort study of adult spinal deformity patients was conducted. Alignment groups were: (1) neutral alignment (NA): coronal vertical axis (CVA) ≤ 3 cm and sagittal vertical axis (SVA) ≤ 5 cm; (2) coronal malalignment (CM) only: CVA > 3 cm; (3) Sagittal malalignment (SM) only: SVA > 5 cm; and (4) coronal and sagittal malalignment (CCSM): CVA > 3 cm and SVA > 5 cm. RESULTS: Of 243 patients, alignment groups were: NA 115 (47.3%), CM 48 (19.8%), SM 38 (15.6%), and CCSM 42 (17.3%). Total instrumented levels (TILs) were highest in CM (14.5±3.7) and CCSM groups (14±4.0) (p<0.001). More 3-column osteotomies (3COs) were performed in SM (21.1%) and CCSM (28.9%) groups than CM (10.4%) (p=0.003). CM patients had more levels instrumented (p=0.029), posterior column osteotomies (PCOs) (p<0.001), and TLIFs (p=0.002) than SM patients. CCSM patients had more TLIFs (p=0.012) and higher estimated blood loss (EBL) (p=0.003) than SM patients. CVA displayed a stronger relationship with TIL (p=0.002), EBL (p<0.001), and operative time (p<0.001) than SVA, which had only one significant association with EBL (p=0.010). Both SM/CCSM patients had higher readmissions (p=0.003) and reoperations (p<0.001) than CM patients. CONCLUSION: Amount of preoperative CM was a better predictor of surgical invasiveness than the amount of SM, despite 3COs more commonly performed in SM patients. CM patients had more instrumented levels, PCOs, and TLIFs than SM patients.