How Reliable is the Assessment of Fusion Status Following ACDF Using Dynamic Flexion-Extension Radiographs?

Study Design: Reliability study.

Objectives: The radiographic diagnosis of non-union is not standardized. Prior authors have suggested using a cutoff of <1 mm interspinous process motion (ISPM) on flexion-extension radiographs, but the ability of practicing surgeons to make these measurements reliably is not clear.