The Effect of Anterior Cervical Discectomy and Fusion on Cervical Sagittal Vertical Axis and Lordosis with Minimum 2-Year Follow-Up

Abstract

Anterior cervical discectomy and fusion (ACDF) can induce lordosis and improve cervical sagittal vertical axis (SVA), but multilevel ACDF may inadvertently increase cervical SVA because of insufficient lordosis induction. Patients who underwent 1-, 2-, or ≥3-level ACDF in the subaxial spine with minimum 2-year follow up were retrospectively studied. C2-C7 Cobb angle (lordosis), cervical SVA, and T1 slope were measured preoperatively, immediately postoperatively, and at last follow-up. Inclusion criteria were met by 127 patients. There were no differences in baseline demographics among 1-, 2-, and ≥3-level ACDF groups. Mean follow-up was 43.7 months (range, 24-142 months). Increase of cervical SVA immediately postoperatively was 1.94 mm,-1.44 mm, and 7.25 mm for 1-, 2-, and ≥3-level ACDF (P= 0.041) and at last follow-up was 2.97 mm, 0.70 mm, and 9.32 mm for 1-, 2-, and ≥3-level ACDF (P= 0.026). At last follow-up, 2-level ACDF patients had the greatest decrease in T1 slope (-0.43°) compared with increase of 2.71° for 1-level and 2.84° for ≥3-level patients (P= 0.028). In all 3 groups, segmental (ACDF levels) lordosis, cervical SVA, and T1 slope did not decrease from immediate postoperative to last follow-up. Only 2-level ACDF maintained C2-7 lordosis (2.16°) compared with loss of lordosis in 1-level (-0.84°) and ≥3-level (-2.00°) ACDF (P= 0.008) at last follow-up. Linear regression analysis showed that T1 slope had no relationship with correction of cervical SVA (P= 0.5310) but had a significant correlation with Cobb angle loss of C2-C7 lordosis (P= 0.0016). Compared with 1- and 2-level ACDF, ≥3-level ACDF resulted in significant increase of cervical SVA and loss of overall lordosis. Compared with 1- and ≥3-level ACDF, 2-level ACDF had the greatest ability to maintain lordosis. T1 slope had a significant correlation with loss of C2-C7 lordosis after ACDF.