This study summary is an excerpt from 2 Minute Medicine’s book The Classics in Medicine: Summaries of the Landmark Trials
1. Magnetic resonance imaging (MRI) of the lumbar spine in individuals without back pain revealed that at least a single intervertebral disc protrusion was common in more than half of the subjects photographed, while more than a quarter had at least a single disc protrusion showed.
2. Other abnormalities were common, including Schmorl’s glands, annulus fibrosis defects, and facet arthropathy, with no significant differences in the prevalence of any particular abnormality between the sexes.
Original Publication Date: July 1994
Study overview: Low back pain remains a difficult management dilemma, given the chronicity of most complaints and the poor symptomatic response to intervention, leading to much unnecessary spinal imaging, with significant costs to the medical system. Even in the face of positive imaging findings, clinicians struggled to correlate symptoms with imaging findings. Prior to this study, the term “herniation” was used to describe the spectrum of intervertebral disc abnormalities seen on MRI, ranging from small protrusions to larger protrusions or even complete protrusions without differentiation. The authors here showed that in individuals without back pain, the prevalence of at least a single disc bulge was 52% on MRI of the lumbar spine, demonstrating an age-dependent association for both the number of discs affected and the prevalence of bulges seen. Disc protrusions were evident in 27% of asymptomatic subjects, while extrusions were found in only 1% of subjects depicted. The vast majority of disc abnormalities were found in the L4-5 and L5-S1 spaces, and least frequently in the L1-2 space. Similarly, findings of Schmorl’s nodes or disc herniation in an adjacent vertebral body endplate, annular defects, and facet arthropathy were observed in 19%, 14%, and 8% of asymptomatic subjects, respectively. These findings, in light of the more specific terminology introduced, showed that disc bulges and protrusions, but not extrusions, are common in the population and could not reliably predict the symptoms of back pain, and may in fact be purely coincidental.
Click to read the research in NEJM
in-depth [prospective cohort]: This prospective study enrolled 98 volunteers with no symptoms of back pain (mean age 42.3 years; 49% female) at a community hospital in California. Exclusion criteria included a history of back pain lasting more than 48 hours or a history of lumbosacral radiculopathies. Each subject underwent 1.5 T MRI of the lumbar spine in both the axial and sagittal planes, and completed a study to score their level of physical activity at baseline from 0 (no exercise) to 4 (five or more workouts per week). ). In addition to the 98 MRIs produced for these subjects, 27 abnormal examinations of the lumbar spine were randomly mixed to reduce interpretation bias. All studies were independently interpreted by a pair of experienced neuroradiologists at an external academic medical center, blinded to the clinical status of the subjects, and the results of the two measurements were averaged for a definitive summary of the data. The specific nomenclature used to describe the intervertebral disc findings was described as follows: normal (with no disc elongation outside the interspace), bulge (with symmetrical elongation of the disc beyond the interspace), protrusion (with asymmetrical elongation of the disc outside the gap), or extrusion (with the extruding disc material having a larger diameter than the remaining disc in the gap).
Of the asymptomatic subjects photographed, 52% had a disc protrusion at at least one level, 27% had at least one protrusion, and only 1% showed an extrusion, for a total of 64% of those without back pain who had a disc deformity. showed at one level and 38% with abnormalities at more than one level. Intervertebral disc abnormalities were most common at the L5-S1 and L4-5 levels, with decreasing prevalence toward the L1-2 level. There were no differences in the prevalence of disc anomalies between the sexes, but an increase in the prevalence of disc bulges was seen with increasing age (p < 0.001) at each disc level. Age also predicted an increase in the prevalence of multiple disc abnormalities (p < 0.001). The physical activity score did not correlate significantly with the number of disc abnormalities visualized. A variety of other non-intervertebral spinal abnormalities were noted among those depicted: most commonly, Schmorl's nodes were observed in 19% of subjects, annulus fibrosis defects in 14%, facet arthropathy in 8% and spondylolysis, spondylolisthesis, central canal stenosis and neural foraminal stenosis were each seen in 7% of the subjects depicted.
Jensen MC, Brant-Zawadzki MN, Obuchowski N, Modic MT, Malkasian D, Ross JS. Magnetic resonance imaging of the lumbar spine in people without back pain. The New England Journal of Medicine. 1994 Jul 14;331(2):69–73.
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