Facet distraction distance independently predicts cage subsidence following anterior cervical discectomy and fusion

This study aimed to evaluate the relationship between facet distraction distance (FDD) and cage subsidence following anterior cervical discectomy and fusion (ACDF). This retrospective study included patients who underwent ACDF for degenerative cervical disease at our institution between 2020 and 2023. Preoperative computed tomography (CT) scans were used to assess Hounsfield unit (HU) values, reflecting bone mineral density (BMD). Disc distraction distance (DDD) and FDD were measured using preoperative, immediate postoperative, and final follow-up radiographs. Multivariate logistic regression analysis was performed to identify independent risk factors for cage subsidence. A total of 80 patients were included in the study. Compared to the non-subsidence group, the subsidence group demonstrated significantly greater DDD (p = 0.001) and FDD (p < 0.001), as well as lower HU values (p = 0.014). Multivariate logistic regression analysis identified lower HU values, greater DDD, and greater FDD as independent risk factors for subsidence. Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve (AUC) for FDD was 0.762, with an optimal threshold of 0.66. FDD is an independent predictor of cage subsidence following ACDF. To reduce the risk of subsidence, over-distraction of the interfacet space should be avoided.