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Differentiating lumbar disc protrusions, disc bulges, and discs with normal contour but abnormal signal intensity.
P C Milette1, S Fontaine, L Lepanto
1Department of Radiology, Hôpital Saint-Luc, Centre Hospitalier de l'Université de Montréal, Quebec, Canada.
Study Design:
Independent evaluation by two observers of 132 lumbar discs in 45 patients with chronic low back pain investigated by both magnetic resonance imaging and discography.
Objectives:
To assess some of the fundamental differences between lumbar disc protrusions, disc bulges, and discs with normal contour but abnormal signal intensity on T2-weighted magnetic resonance images.
Summary Of Background Data:
Moderate interobserver agreement has been reported when the morphologic terms normal, bulge, protrusion, and extrusion are used. The validity of this nomenclature remains unknown.
Methods:
Discs were evaluated on magnetic resonance images for central and peripheral signal characteristics, height, contour, and nerve root compression. Discograms were classified according to degrees of disc degeneration, disruption, and pain reproduction.
Results:
Loss of intervertebral height or abnormal signal intensity on magnetic resonance imagery was significantly associated with disc disruptions extending into or beyond the outer anulus on discograms. All 23 protrusions (100%) and 12 of 15 disc bulges (80%) were associated with Stage 2 or 3 anular disruptions and, in most instances, similar or exact reproduction of pain during disc injection. There was no significant difference between disc protrusions, disc bulges, and discs with normal contour but abnormal signal, with respect to degree of disc degeneration, extent of disruptions, or presence of discogenic pain.
Conclusions:
In patients with chronic low back pain, loss of disc height or abnormal signal intensity is highly predictive of symptomatic tears extending into or beyond the outer anulus. Disc bulges and disc protrusions do not represent discs with significantly different internal architecture, based on the findings of discography, and are no more suggestive of symptomatic tears than discs showing normal contour but decreased height or abnormal signal intensity.