Cervical sagittal balance parameters after single-level anterior cervical discectomy and fusion: Correlations with clinical and functional outcomes

BACKGROUND: Normal sagittal cervical alignment has been associated with improved outcome after anterior cervical discectomy and fusion (ACDF). OBJECTIVE: The aim of this study is to identify alterations of cervical sagittal balance parameters after single-level ACDF and assess correlations with postoperative functionality. METHODS: A retrospective chart review was performed between January 2010 and January 2014 to identify adult patients with no previous cervical spine surgery who underwent ACDF at any one level between C2 and C7 for the single-level degenerative disease. Tumor, infection, and trauma cases were excluded from the study. For the included cases, the following data were recorded preoperatively and 6 months–1 year after surgery: sagittal balance-marker measurements of the C1–C2 angle, C2–C7 angle, C7 slope, segmental angle at the operated level, and sagittal vertical axis (SVA) distance between C2 and C7, as well as the neck disability index and visual analog scale of pain. RESULTS: The present study included 47 patients (average age: 51.2 years; range: 28–86 years). A moderate negative correlation between a smaller C2–C7 angle and the presence of right arm pain before treatment was found (P = 0.0281). Postoperatively, functionality scores significantly improved in all patients. C1–C2 angle increased with statistical significance (P = 0.0255). C2–C7 angle, segmental angle, C7 slope, and SVA C2–C7 distance did not change with statistical significance after surgery. C7 slope significantly correlated with overall cervical sagittal balance (P < 0.05). CONCLUSIONS: Single-level ACDF significantly increases upper cervical lordosis (C1–C2) without significantly changing lower cervical lordosis (C2–C7). The C7 slope is a significant marker of overall cervical sagittal alignment (P < 0.05).