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MR image-based grading of lumbar nerve root compromise due to disk herniation: reliability study with surgical
Christian W A Pfirrmann1, Claudio Dora, Marius R Schmid
1Department of Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. christian@pfirrmann.ch
Abstract:
A system for grading lumbar nerve root compromise (no compromise, contact of disk material with nerve root, deviation of nerve root, and compression of nerve root) was tested in the interpretation of routine magnetic resonance images of 500 lumbar nerve roots in 250 symptomatic patients. Intra- and interobserver reliability was assessed for three independent observers. In the 94 nerve roots evaluated at surgery, surgical grading was correlated with image-based grading. kappa statistics indicated substantial agreement between different readings by the same observer and between different observers (for intraobserver agreement, kappa = 0.72-0.77; for interobserver agreement, kappa = 0.62-0.67). Correlation of image-based grading with surgical grading was high (r = 0.86). The image-based grading system enabled reliable evaluation and reporting of nerve root compromise.