Contiguous Two-Level Anterior Cervical Discectomy and Fusion Using Zero-P VA System: A Retrospective Study.

Purpose: The aim of this study was to explore short-term radiological findings after contiguous two-level ACDF with Zero-P VA devices.

Methods: Patients who underwent contiguous two-level anterior cervical discectomy and fusion (ACDF) from C3 to C7 with a Zero-P VA system were followed. Cervical anteroposterior and lateral X-rays and functional outcomes were assessed 3 months after surgery.

Results: Overall, 34.9% of patients had prosthesis subsidence and 74.6% screw loosening. Up to 46.8% of the patients with screw loosening also experienced prosthesis subsidence compared with 0 patients without screw loosening (p=0.0005). The screw-loosening rate was 91.7% in patients with poor positioning of the screw/cage and 70.6% in patients without poor positioning of the screw/cage, but no statistical difference was found between the groups (p=0.267). The subsidence rate was 50% in patients with poor positioning of the screw/cage and 31.4% in patients without poor positioning of the screw/cage, but no statistical difference was found between the groups (p=0.314). VAS scores of patients with prosthesis subsidence were much higher than those without (p=0.031), but this difference was not found for patients with or without screw loosening (p=0.116). The NDI scale was much higher in patients regradless of screw loosening or subsidence.

Conclusion: Screw loosening and prosthesis subsidence happen frequently after contiguous two-level ACDF with Zero-P VA. Screw loosening seems to be the only risk factor for prosthesis subsidence.