Reliability and Accuracy of MRI Laminar Angle Measurements to Determine Intra-Procedural Contralateral Oblique View Angle for Cervical or Thoracic Interlaminar Epidural Steroid Injections.

Background And Objective: Contralateral oblique (CLO) angle view has been a useful addition to standard views in fluoroscopically guided interlaminar epidural injections. Determination of the appropriate CLO angle is paramount in the usefulness of this technique. Using MRI laminar angle measurements as a pre-procedural guide for the intra-procedural fluoroscopic CLO angle has been proposed. The purpose of this study was to help determine if using axial MRI laminar measurements prior to a cervical or thoracic epidural steroid injection would be useful in predicting the appropriate fluoroscopic CLO angle.

Study Design: A retrospective review was performed for patients who underwent cervical or thoracic interlaminar injections. In the performance of interlaminar injections, the authors had routinely determined the true fluoroscopic contra-lateral oblique angle after epidural access was confirmed, for use during any potential future injections. The fluoroscopic CLO angle measurements were obtained from a chart review and compared blindly to each patient's MRI axial laminar angle measurements.

Results: 34 injections were included. Inter-rater reliability comparing the two authors' MRI angle measurements was considered fair, ICC = 0.395. Accuracy was only 57% comparing MRI laminar angle measurements to within five degrees of the true fluoroscopic CLO angle as determined during the injection procedure. Accuracy by ICC showed only fair agreement, 0.47 and 0.22, for the two authors.

Conclusions: The findings of this study indicate fair inter-rater reliability in manual measurements of laminar angle on axial MRI images. MRI laminar angle measurements do not appear to be highly accurate in determining the appropriate fluoroscopic CLO angle.