This study summary is an excerpt from the book 2 Minute Medicine’s 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 disk bulge was prevalent in over half of those imaged, while over a quarter showed at least a single disk protrusion.
2. Other abnormalities were common, including Schmorl’s nodes, defects of the annulus fibrosis, and facet arthropathy, without significant differences in the prevalence of any given abnormality between the sexes.
Original Date of Publication: July 1994
Study Rundown: Low back pain remains a difficult management dilemma given the chronicity of most complaints and poor symptomatic response to intervention, leading to a great deal of unnecessary spinal imaging at significant cost to the medical system. Even in light of positive findings on imaging, clinicians have had difficulty correlating symptoms to imaging findings. Prior to this study, the term “herniation” was used to describe the spectrum of intervertebral disk abnormalities seen on MRI ranging from small bulges, to larger protrusions or even complete extrusions without differentiation. The authors here showed that among individuals without back pain, the prevalence of at least a single disk bulge was 52% on MRI of the lumbar spine, with an age-dependent association demonstrated for both the number of disks affected and the prevalence of bulges seen. Disk protrusions were evident in 27% of asymptomatic individuals, while extrusions were found in only 1% of those imaged. The vast majority of disk abnormalities were found at the L4-5 and L5-S1 spaces, and least commonly at the L1-2 space. Similarly, findings of Schmorl’s nodes, or disk herniation into an adjacent vertebral body end plate, annular defects, and facet arthropathy were seen in 19%, 14%, and 8% of asymptomatic subjects, respectively. These findings, in light of the more specific terminology introduced, demonstrated that disk bulges and protrusions, but not extrusions, were highly prevalent in the population and could not reliably predict symptoms of back pain, and in fact may be purely coincidental.
In-Depth [prospective cohort]: This prospective trial enrolled 98 volunteers without back pain symptoms (mean age 42.3 years; 49% female) at a community hospital in California. Exclusion criteria included a history of back pain lasting greater than 48 hours or any history of lumbosacral radiculopathies. Each subject underwent 1.5T MRI of the lumbar spine in both the axial and sagittal planes, and completed a survey to score their level of baseline physical activity from 0 (no exercise) to 4 (five or more workouts per week). In addition to the 98 MRIs produced for these subjects, 27 abnormal studies of the lumbar spine were randomly intermixed to reduce interpretation bias. All studies were interpreted independently by a pair of experienced neuroradiologists at an outside academic medical center blinded to the clinical status of the study subjects, and results of the two readings were averaged for final summary of the data. The specific nomenclature used to describe intervertebral disk findings was described as follows: Normal (without disk extension beyond the interspace), bulge (with symmetric extension of the disk beyond the interspace), protrusion (with asymmetric extension of the disk beyond the interspace), or extrusion (with the extruding disk material larger in diameter than the remaining disk in the interspace).
Among the asymptomatic individuals imaged, 52% had a disk bulge at least one level, 27% demonstrated at least one protrusion, and only 1% demonstrated an extrusion, for a total of 64% of those without back pain demonstrating a disk abnormality at one level and 38% with abnormalities at more than one level. Abnormalities of the intervertebral disks were most prevalent at the L5-S1 and L4-5 levels, with a decreasing prevalence toward the L1-2 level. There were no differences in the prevalence of disk abnormalities between the sexes, but an increase in the prevalence of disk bulges was seen with increasing age (p <0.001) at every disk level. Age also predicted an increase in the prevalence of multiple disk abnormalities (p <0.001). The physical activity score did not correlate significantly to the number of visualized disk abnormalities. A variety of other, non-intervertebral disk spinal abnormalities were noted among those imaged: Most commonly, Schmorl’s nodes were noted in 19% of subjects, defects of the annulus fibrosis in 14%, facet arthropathy in 8%, and spondylolysis, spondylolisthesis, central canal stenosis, and neural foraminal stenosis were each seen in 7% of imaged subjects.
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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