Development of new-onset cervical deformity in nonoperative adult spinal deformity patients with 2-year follow-up

Purpose: Evaluate the presence of new-onset cervical deformity (CD) in nonoperative adult spinal deformity (ASD) patients with extended follow-up, with consideration for predictors, prevalence, and impact on patient-reported outcomes. Methods: Retrospective review of a prospective nonoperative ASD cohort. New onset CD patients at 1- (CD-1Y) and 2-year (CD-2Y) follow-up were defined as displaying baseline cervical alignment. Univariate analyses determined differences in radiographic parameters and outcome scores of CD and maintained-cervical-alignment patients. Multivariate binary logistic regression models determined new-onset CD predictors. Results: A total of 143 patients were included (mean age 54 years, mean body mass index 25.6 kg/m ² , 86% female). Cervical deformity rate was 38.5% at baseline. New-onset CD incidence at 1- and 2-year follow-up was 30.0% and 41.7%, respectively. Global sagittal profile comparison of CD-1Y/CD-2Y versus maintained cervical alignment cases revealed no differences (P . .05) at any interval. Baseline C2-C7 sagittal vertical axis (SVA) was associated with increased new-onset CD risk at 1 (odds ratio [OR] 1.14, P ¼ .025) and 2 years (OR 1.04, P ¼ .032); prior spine surgical history was associated with CD risk at 1-year follow-up (OR 6.75, P ¼ .047); baseline C2 slope was associated with increased CD risk at 2-year follow-up (OR 1.12, P ¼ .041). CD development did not significantly impact health-related quality of life (P . .05). Conclusions: Cervical deformity can manifest in nonoperative ASD patients: 30.0% at 1-year follow-up, and 41.7% at 2-year follow-up. Progressive CD manifested independently of thoracolumbar profile changes. Increased baseline C2-C7 SVA, C2 slope, and prior surgical history increased new-onset CD odds at 1 and 2 years.