Evaluation of fusion status after spine fusion surgery: a comprehensive review

Accurate assessment of fusion status following spinal fusion surgery is paramount, as it closely relates to patient outcomes and quality of life. Multiple imaging modalities have been developed to evaluate fusion, each with distinct advantages and limitations. Plain radiography remains the most accessible and practical method, with dynamic flexion-extension radiographs providing reasonably reliable information on segmental motion and stability. Computed tomography offers superior spatial resolution and enables direct visualization of trabecular bone bridging between vertebral segments, making it the most accurate modality for confirming fusion. Magnetic resonance imaging and radionuclide imaging can serve as complementary techniques, particularly when conventional methods are inconclusive or contraindicated. This review summarizes the strengths and limitations of each imaging modality used for assessing spinal fusion. It also highlights recent technological advances and emerging diagnostic approaches that may enhance the objectivity, reliability, and accuracy of fusion assessment in the future.