Does Bone Preservation at the Anterior Edge of the Vertebral Body Affect the Subsidence of Zero-Profile Cages After Anterior Cervical Discectomy and Fusion?

OBJECTIVE: The purpose of this study was to investigate whether the preservation of the anterior edge of the vertebral body affects the cage subsidence and clinical outcomes after anterior cervical discectomy and fusion (ACDF) using zero-profile cages. METHODS: We retrospectively analyzed 86 patients who underwent 1-3 levels of ACDF using zero-profile cages between December 2017 and June 2023. According to whether the anterior edge was protected, the patients were divided into an intact group and a defect group. Cage subsidence was defined as a double dagger 2 mm decrease in vertebral height at follow-up compared with measurement on postoperative day 2. The patients' radiological parameters and clinical outcomes were also analyzed. RESULTS: The subsidence rate was 17.02% (8/47) in the intact group and 41.03% (16/39) in the defect group (P = 0.014). At the last follow-up, all patients in both groups achieved complete intervertebral fusion. The cervical lordosis of the 2 groups was effectively restored after surgery, and the visual analog scale and Neck Disability Indexscores of the 2 groups were significantly improved. Multivariate logistic regression analysis showed that the protective factor for zero-profile cage subsidence was bone protection at the anterior edge of the vertebral body (odds ratio = 0.270; 95% confidence interval = 0.0910.804), and the risk factor was related to the height of the preoperative surgical segment (odds ratio = 2.285; 95% confidence interval = 1.395-3.743). CONCLUSIONS: For patients who undergo ACDF with zero-profile cages, especially those with a higher surgical segment, bone protection at the anterior edge of the vertebral body can effectively reduce the risk of zero- profile cage subsidence, but there is no difference in the final clinical effect.