Neurosurgeon Midwest Spine and Brain Lakewood, Colorado, United States
Introduction: Given the clinical and economic cost of symptomatic pseudarthroses, having a radiographic gold standard to appropriately evaluate a spinal fusion is of clinical significance. Imaging techniques include plain radiographs, flexion and extension radiographs and computed tomography (CT) scans can be used to determine fusion. Although numerous imaging techniques and objective evaluation criteria have been employed, advances in technology potentially limit the application of prior research techniques. The aim of this study was to determine the current state-of-the-art for fusion evaluation in the lumbar spine.
Methods: A systematic review of literature was performed to evaluate imaging methodologies and spinal fusion criteria within high quality spine studies. PubMed was searched for relevant articles using the following search terms: Graft AND anterior cervical discectomy and fusion OR cervical fusion OR interbody fusion OR posterolateral fusion AND prospective OR randomized. Full text English language articles considering spinal fusion published from 2017 were eligible. Prospective or randomized studies were included to identify methodologies associated with high quality research often used for regulatory purposes or to inform on policy of clinical best practice. Non-clinical studies and those studies in which spinal fusion were not assessed were excluded.
Results: A total of 132 articles were screened and 19 (cervical n=3; lumbar n=16) eligible for review. The procedure distribution was as follows: ACDF=3; TLIF=6; PLIF=2; XLIF=1; PLF=7. Fusion was assessed using plain radiographs (n=1), dynamic radiographs (n=3), CT (n=11) and CT and dynamic radiographs (n=4). Most publications (n=11) used fine cut CT scans to assess for bridging bone; however, the CT acquisition parameters varied between 0.7mm to 2mm slice thickness. Although trends exist, the objective criteria for spinal fusion were inconsistent among publications. Independent radiological assessment of spinal fusion was not applied in all high-level publications.
Conclusion : Fine cut CT scans are consistently employed in high level studies and are considered the standard for non-invasive evaluation of spinal fusion. Advances in imaging technology provide reduced slice thickness and improve visualization for fusion assessment; however, objective radiographic fusion criteria vary between studies and should be considered carefully for comparative assessment.
