Risk factors for postoperative subsidence of single-level anterior cervical discectomy and fusion: the significance of the preoperative cervical alignment.

STUDY DESIGN: Retrospective cohort study.

OBJECTIVE: To investigate and analyze the preoperative risk factors affecting subsidence after anterior cervical discectomy and fusion (ACDF) to reduce subsidence.

SUMMARY OF BACKGROUND DATA: Subsidence after ACDF may be caused by various risk factors, although the related information is scarce.

METHODS: Seventy-eight patients who underwent single-level ACDF between 2005 and 2011 were included. Patients were categorized into the subsidence (n = 26) and nonsubsidence groups (n = 52). Preoperative factors such as age, sex, operative level, bone mineral density, cervical alignment, segmental sagittal angle, and anterior/posterior disc height were assessed. The use of plates and the anterior/posterior disc height gap were examined as perioperative factors. The clinical outcome was assessed using a visual analogue scale for neck and arm pain.

RESULTS: Subsidence occurred in 26 (33.3%) of 78 patients. A significant difference was found in clinical outcomes between the subsidence and nonsubsidence groups (P < 0.05). The fusion rate was 61.5% in the subsidence group. The mean time to subsidence was 4.8 months. Logistic regression analysis revealed that cervical alignment (P = 0.017), age (P = 0.022), and use of plates (P = 0.041) affected subsidence. In patients who received a stand-alone cage, the risk of subsidence was significantly greater in the kyphotic angle group than in the lordotic angle group (odds ratio = 13.56; P < 0.001).

CONCLUSION: After ACDF, the main factors affecting subsidence are cervical alignment, age, and use of plates. Our data suggest that surgeons should consider the kyphotic curvature and/or age when deciding on the use of plates.