Inter- and Intra-observer Reliability of MRI for Lumbar Lateral Disc Herniation

BACKGROUND The authors analyzed inter- and intra-observer agreement with respect to interpretation of simple magnetic resonance T1- and T2-weighted axial and sagittal images for the diagnosis of lumbar lateral disc herniation, including foraminal and extraforaminal disc herniations. METHODS Forty-two patients in whom lumbar lateral disc herniation was suspected or confirmed by simple magnetic resonance imaging at one institute between May 2003 and December 2004 were included. The magnetic resonance images consisting of T1- and T2-weighted axial and sagittal images, and these were reviewed blindly and independently by three orthopaedic spine surgeons in a random manner. The images were interpreted as positive or negative for lateral disc herniation on 2 different occasions 3 months apart. Results were analyzed using Cohen's kappa statistic, and strengths of agreements were determined using the Landis and Koch criteria. RESULTS The kappa values for inter-observer agreement averaged 0.234 (0.282, 0.111, and 0.308 respectively) on the first occasion, and 0.166 (0.249, 0.111, and 0.137 respectively) on the second occasion, with an overall mean value of 0.200. Thus, the strength of agreement was only slight-to-fair according to the Landis and Koch criteria. Kappa values for intra-observer agreement averaged 0.479 (0.488, 0.491, and 0.459 respectively), indicating moderate agreement. CONCLUSIONS The present study indicates that simple magnetic resonance imaging is not a reliable imaging modality for diagnosing lumbar lateral disc herniation. Another imaging study with improved diagnostic values should be developed to diagnose this pathologic finding.