Dynamic Instability Is Underestimated on Standing Flexion-Extension Films When Compared With Prone CT Imaging

Area of Science:

• Radiology
• Orthopedics
• Spine Surgery

Background:

• Dynamic lumbar instability can be underestimated by standard flexion-extension radiographs.
• Current guidelines lack consensus on optimal imaging for evaluating instability.
• Accurate assessment of spondylolisthesis is crucial for effective treatment planning.

Purpose of the Study:

• To evaluate the incidence and degree of L4-5 anterior spondylolisthesis using different imaging modalities.
• To compare the sensitivity of prone CT, standing flexion-extension radiographs, and supine MRI in detecting instability.
• To determine if prone CT imaging is superior for assessing lumbar instability.

Main Methods:

• A retrospective cohort study of 102 patients with L4-5 anterolisthesis.
• Comparison of imaging data from standing lateral conventional radiographs (CR), flexion-extension images, prone CT (CT), and supine MRI (MRI).
• Quantitative analysis of anterolisthesis measurements and statistical comparison between modalities.

Main Results:

• Prone CT demonstrated a greater degree of L4-5 segmental instability compared to CR and MRI.
• Significant differences in anterolisthesis measurements were observed between CR and CT (P<0.001), and CR and MRI (P<0.001).
• 38.2% of patients showed ≥3 mm anterior translation on CR compared to CT, versus 17.6% comparing CR to MRI.

Conclusions:

• Prone CT imaging is more sensitive in revealing the degree of single L4-5 segmental instability.
• Conventional radiographs may underestimate spondylolisthesis compared to prone CT.
• Prone CT offers a more comprehensive evaluation of dynamic lumbar instability.