A New Potential Complication in 2-Level Anterior Cervical Discectomy and Fusion with Zero-Profile Devices: Collapse of the Middle Cervical Vertebra

The objective of this study was to describe a new potential complication, collapse in the middle cervical vertebra of consecutive 2-level anterior cervical discectomy and fusion (ACDF), and discuss its possible mechanism.Clinical and radiologic outcome data from 27 consecutive 2-level ACDF patients using zero-profile devices were collected at 1, 3, 6, and 12 months postoperatively, as well as the last follow-up. Dysphagia was assessed using the Bazaz score, and clinical outcomes were analyzed using the neck disability index and Japanese Orthopaedic Association score. Radiographic evaluation included measurements of the overall and surgical segment curvature, identification of collapse, and assessment of the ratio of anterior height and wedge of the upper, middle, and lower vertebrae in the surgical segment.The application of zero-profile devices to treat consecutive 2-level cervical spondylosis mostly resulted in good midterm clinical outcomes. Surprisingly, as evidenced by the significantly decreased anterior height and wedge ratio of the middle cervical vertebra, collapse was noted immediately in the middle vertebra in 4 patients at 1 month (n = 3) and 3 months (n = 1). The collapse increased for no more than 6 months, and there was no deterioration of clinical and radiological outcomes at the last follow-up.Collapse in the middle cervical vertebra of consecutive 2-level ACDF with the application of zero-profile devices can occur in the early postoperative period, which may be due to axial stress concentration and blood supply damage in the middle cervical vertebral body.