Radiological Factors Affecting Cage Subsidence after Single-level Anterior Cervical Discectomy and Fusion with Double Titanium Cylindrical Cages

Anterior cervical discectomy and fusion has become established as a standard surgical method for degenerative cervical disease. Various materials have been used, and we currently usually use double titanium cylindrical cages. Many investigators have reported on the incidence of subsidence after anterior cervical discectomy and fusion. This study focused on the radiological position of the inserted cages and radiological factors influencing the surgical method and examined their relationship with subsidence. Participants in this retrospective study comprised 112 patients diagnosed with cervical myelopathy and radiculopathy caused by disc herniation and spondylosis who underwent one-level anterior cervical discectomy and fusion at a single institution between September 2012 and December 2022. Subsidence was defined as a ≥3-mm decrease in segmental disc height on lateral X-ray at the 1-year follow-up compared to that on postoperative day 1. Subsidence was identified in 53 patients (47.3%). At the view of radiological cage position, our univariate analysis demonstrated that the only deviation of the inserted cages from the anatomical center on the anterior-posterior view was significantly associated with subsidence. Inserting cages in a central position thus appears important to prevent radiological subsidence after anterior cervical discectomy and fusion. Despite high subsidence rates, no patients required additional procedures at the same level by the end of the minimum 2-year follow-up period.