Radiographic fusion and subsidence rates for stand-alone cage versus anterior cage-plate construct in ACDF

Study Design

Retrospective cohort

Background

The addition of an anterior cervical plate to a structural allograft during ACDF is thought to provide extra stability and enhance fusion, but it may increase the risk of complications like dysphagia. Stand-alone cages were designed to provide this extra stability without the need for the plate, but these may increase a patient's risk of subsidence, cervical dislocation, and cervical kyphosis. The purpose of this study was to assess reoperation rates and radiographic outcomes during follow-up longer than 6 months for patients who underwent ACDF with a cage and plate compared to stand-alone cage.

Methods

ACDF cases were retrospectively identified for four fellowship trained spine surgeons from 2016 – 2020 from two academic hospitals. A total of 57 stand-alone structural allograft constructs were matched via propensity scoring with a cohort of 65 patients with plate-secured structural allograft constructs. The primary outcome was reoperation rate within the follow-up period and secondary outcomes included complications, operative characteristics, readmission within 30 days, reoperation within 30 days and within follow-up, and radiographic outcomes. Immediate post-operative radiographs were compared to final follow-up radiographs at least 6 months post-operation to assess for evidence of subsidence, fusion, and change in cervical kyphosis using the Cobb angle technique.

Results

There were 5 patients (5.26 %) in the stand-alone cohort and 4 patients (3.15 %) in the plate cohort that had cervical reoperation at any time in follow-up (P = 0.83). At final follow-up, 58 patients (92.1 %) in the plate group and 37 patients (75.5 %) in the stand-alone group had radiographic evidence of fusion (P = 0.015). There were 38 patients (77.6 %) in the stand-alone group and 29 patients (46 %) in the plate group with evidence of subsidence (P = 0.0007). Patients with subsidence had a greater change in kyphosis angle at final follow-up and this change was significantly decreased in the plate group compared to the stand-alone group.

Conclusion

The use of anterior cage-plate constructs in ACDF produces higher rates of fusion and lower rates of subsidence than stand-alone cage constructs. Subsidence significantly increases the change in kyphosis angle between post-op and final follow-up, and the presence of a spanning plate significantly reduces this angle change compared to stand-alone cages. There were no statistically significant differences in reoperation rates, regardless of radiographic evidence of subsidence.