Risk of Development of New Onset Postoperative Cervical Deformity in Thoracolumbar Adult Spinal Deformity and Effect on Clinical Outcomes at 2-Year Follow-Up

Abstract

Introduction A high prevalence of residual cervical deformity (CD) has been identified following surgical treatment of adult spinal deformity (ASD). Development of the new onset CD is less understood and its clinical impact unclear. This study quantifies the incidence of new onset CD after ASD surgery, identifies predictors of development, and determines the impact outcomes. Materials and Methods Retrospective review of a prospective multicenter database yielded 215 patients (pts) with complete 2-year follow-up and full length X-rays including the cervical spine. CD was defined by T1S–CL > 20 degrees, C2C7 SVA > 40 mm, or C2C7 kyphosis > 10 degrees. Univariate analysis was performed using t tests or tests of proportion. Multivariate logistic regression was used to determine independent predictors of new CD. The impact of CD on health-related quality of life (HRQL) and satisfaction was measured using repeated measures mixed models or logistic regression as appropriate, accounting for potential confounders. Results Of the 215, 88 pts with ASD did not have CD at baseline and 42 of them (47.7%) developed CD at 2 years' postoperatively. Univariate analysis revealed that pts who developed new CD in the postoperative period had a higher incidence of diabetes (14.29 vs. 2.17%, p = 0.036) increased preoperative C2C7 SVA ( p = 0.04) and C2 slope ( p = 0.038) and smaller diameter rods used at surgery ( p = 0.0328). Independent predictors of new CD at 2 years included diabetes (OR, 10.49; p = 0.046) and increased preoperative TS–CL (OR, 1.08/deg, p = 0.027). Ending instrumentation below T4 was a negative predictor of CD (OR, 0.31; p = 0.019). Pts with and without CD experienced improvements in 2-year SF-36 ( p = 0.0001), ODI ( p = 0.0001), and SRS ( p = 0.0001). Rates and overall improvement were similar. CD was not associated with decreased satisfaction ( p = 0.28). Conclusion Overall, 47.7% of pts without preoperative CD develop new postoperative CD after ASD surgery. Independent predictors of new onset CD at 2 years include diabetes, higher preoperative TS–CL, and ending instrumentation above T4. Significant improvements in HRQL scores occurred despite the development of postoperative CD.