Analysis of adverse sagittal alignment after anterior cervical discectomy and fusion (ACDF) for degenerative cervical myelopathy with local kyphosis

The aim of this study was to identify relevant factors associated with sagittal malalignment, which refers to the loss of lordosis or recurrence of kyphosis following an anterior cervical approach. Degenerative cervical kyphosis has increasingly attracted clinical attention, but there are few studies about the classification of local kyphosis and risk factors of adverse sagittal alignment (ASA) after anterior surgery. The study retrospectively reviewed 82 patients with degenerative cervical myelopathy and local kyphosis who underwent anterior cervical discectomy and fusion (ACDF) between January 2019 and December 2021. The patients' baseline characteristics and postoperative assessments were reviewed using electronic medical records from a single-institution database. Based on the postoperative ASA, the patients were divided into the maintaining and adverse groups. Bivariate and multivariate statistical analyses were performed to predict related factors of the ASA. Comparing the two groups, advanced age (p = 0.019), the classification of local kyphosis (p = 0.001), and preoperative thoracic 1 (T1) slope angle (p < 0.001), C2-7 sagittal vertical axis (SVA) (p < 0.001), C2-7 range of motion (ROM) (p = 0.001), and postoperative adjacent segment degeneration (ASD) (p = 0.009), neck disability index (NDI) (p < 0.001), visual analogue score (VAS) (p < 0.001) were significantly different. Multiple linear regression analysis results for relevant factors of the change of local and C2-7 kyphosis showed classification of kyphosis (p = 0.007 and p = 0.563, respectively), T1 slope angle (p = 0.018 and p = 0.004, respectively), C2-7 SVA (p = 0.109 and p = 0.017, respectively), C2-7 ROM (p = 0.028 and p = 0.007, respectively). Our data suggest that postoperative ASA affects recovery of neck pain, and is related to preoperative T1 slope, C2-7 SVA, C2-7 ROM, and the classification of kyphosis.