Practical Methods of Assessing Coronal Alignment and Outcomes in Adult Spinal Deformity Surgery: A Comparative Analysis.

STUDY DESIGN: Asymptomatic cohort: prospective, cross-sectional, multi-center. Symptomatic: retrospective, multi-surgeon, single-center.

OBJECTIVE: To assess the association between cranial coronal alignment and adult spinal deformity (ASD) surgical risk and outcomes.

SUMMARY OF BACKGROUND DATA: ASD leads to decreased quality of life. Studies have shown that coronal malignment (CM) is associated with worse surgical outcomes.

METHODS: 468 adult participants were prospectively enrolled in the asymptomatic cohort. 172 symptomatic ASD patients with 2-year follow-ups were retrospectively enrolled in the symptomatic cohort. Three cranial plumb line parameters: the positions of the plumb lines from the midpoint between the medial orbital rims (ORB-L5), the odontoid (OD-L5), and the C7 centroid (C7-L5) relative to the L5 pedicle, were measured. Each subject had plumb line medial (M), touching (T), or lateral (L) to either pedicle. The association between each group of patients and radiographic parameters, intraoperative variables, patient-reported outcomes (PROs), and clinical outcomes were analyzed.

RESULTS: In the asymptomatic cohort, OD-L5 was medial to or touching the L5 pedicle in 98.3% of volunteers. In the symptomatic patients, preoperative OD-L5-L exhibited higher mean age (56.2±14.0), odontoid-coronal vertical axis (OD-CVA) (5.5±3.3 cm), Oswestry Disability Index (ODI) score (40.6±18.4), pelvic fixation rate (56/62, 90.3%), OR time (528.4±144.6 min), median estimated blood loss (EBL) (1300cc), and durotomy rate (24/62, 38.7%). A similar pattern of higher CVA, preoperative ODI, intraoperative pelvic fixation rate, OR time, EBL, and durotomy rate was observed in ORB-L5-L and C7-L5-L patients. Final follow-up postoperative OD-L5-L was associated with higher rates of proximal junctional kyphosis (PJK) (13.0%) and pseudarthrosis (17.4%).

CONCLUSION: Preoperative OD-L5, ORB-L5, and C7-L5 lateral to pedicles were associated with worse preoperative ODI and higher intraoperative complexity. Postoperative OD-L5-L was associated with higher rates of PJK and pseudarthrosis. Postoperative CM, approximated by cranial plumb line lateral to the L5 pedicles, was associated with sagittal plane complications.