Radiological Assessment of Lumbar Fusion Status: Which Imaging Modality is best Assessing Non-Union in Lumbar Spine Pseudoarthrosis?

Introduction: Lumbar Disc Degenerative Disease (LDDD) is the leading cause of low back pain and disability globally, particularly in the aging population. Lumbar Interbody Fusion (LIF) surgery is the standard treatment for a variety of lumbar spine conditions, including degenerative, traumatic, infectious, and tumoral pathologies. Despite its widespread use, LIF can lead to complications such as pseudoarthrosis, a condition characterized by failed spinal fusion and incomplete osseous bridging over a year post-surgery. This systematic review examines current radiographic techniques used to assess lumbar fusion outcomes.

Methods: We followed PRISMA guidelines to conduct a systematic review of PubMed, Embase, Google Scholar, and Cochrane Library databases, focusing on articles in English. We included studies involving patients aged 18 and older who had undergone lumbar interbody or posterolateral fusion with at least one year of radiographic follow-up. The primary outcomes analyzed were sensitivity, specificity, and the correlation of radiographic findings with surgical exploration, the gold standard for fusion assessment.

Results: Thirteen studies, published between 1989 and 2019, met the inclusion criteria. These studies primarily originated from North America and Europe, with a majority being retrospective. The review covered a total of 715 patients, with mean ages ranging from 42 to 78 years. Surgical approaches were predominantly open posterior.
The reviewed studies employed various imaging techniques, including Plain Radiographs, Dynamic or Flexion-Extension Radiographs, Computed Tomography (CT), Single Proton Emission-CT (SPECT), Bone Scintigraphy, Magnetic Resonance Imaging (MRI), and Ultrasonography. CT was the most frequently used and showed a wide range of sensitivity (53%-100%) and specificity (78%-96.7%). Flexion-extension radiographs, while common,
demonstrated high variability in sensitivity and specificity, making them less reliable, especially in the presence of lumbar instrumentation. MRI and ultrasonography were the least employed techniques, with limited data supporting their use.

Conclusion : Current imaging techniques for assessing lumbar fusion vary widely in reliability and accuracy. CT scans, with advanced reconstruction techniques, are the most dependable, but no single modality has been universally endorsed. Further research is needed to standardize imaging criteria for better clinical outcomes in LIF patients.