Comparison of Two-Screw versus Four-Screw Internal Fixation on Fusion Speed in Anterior Cervical Discectomy and Fusion: A Prospective Randomized Controlled Trial.

Background Context: The insertion process of the new two-screw internal fixation is simpler than that of four-screw internal fixation for anterior cervical discectomy and fusion (ACDF). However, it is unclear whether there is a difference in fusion rate.

Purpose: This study aimed to compare the time required to achieve osseous fusion and the clinical efficacy of four-screw versus two-screw internal fixation.

Study Design: Prospective randomized controlled trial.

Patient Sample: From October 2021 to April 2023, eighty patients diagnosed with single-level cervical spondylosis were recruited and randomly allocated into a four- or two-screw group.

Outcome Measures: The primary endpoint was the fusion rate six months postoperatively. Secondary outcomes included the prevalence of complications and patient-reported outcome measures (PROMs), including the Japanese Orthopaedic Association score, Neck Disability Index, and visual analog scale scores for arm and neck pain.

Methods: Patients were randomized to receive four-screw internal fixation (n=40) or two-screw internal fixation (n=40).

Results: A total of 77 patients completed the trial and were included in the analysis. No significant differences were observed between groups at baseline. The fusion rate in the two-screw group was significantly higher than that in the four-screw group (69.2% vs. 42.1%, P=0.022) at six months postoperatively. No significant difference was found in the fusion rates at 3 and 12 months postoperatively between groups. Overall, PROMs significantly improved after surgery in both groups and did not differ significantly between groups at any follow-up time point. The prevalence of complications was not significantly different between groups.

Conclusions: Two-screw internal fixation can achieve osseous fusion faster than four-screw internal fixation in ACDF. Two-screw internal fixation seems to achieve the same PROMs and safety as four-screw internal fixation.