A prospective observational study of patients with low back pain and those without was performed.
To investigate the prevalence and significance of a high-intensity zone in a group of patients asymptomatic for low back pain, but who had known risk factors for lumbar disc degeneration. This asymptomatic group was compared with a symptomatic group of patients with respect to the presence of anular high-intensity zone and the pain response with discography.
Some authors have estimated the prevalence of a high-intensity zone in a group of symptomatic patients to be 86%. They have reported a strong correlation between a high-intensity zone and positive discography in patients with low back pain. Other investigators have reported evidence either supporting or discounting these findings.
Patients with low back pain and those without underwent physical examination, psychometric testing, plain radiograph, magnetic resonance imaging, and discography. The presence of a high-intensity zone, anular disruption, and positive discographic pain then were compared between the two groups. There were strict inclusion criteria for both groups. A total of 109 discs in 42 patients were evaluated in the symptomatic group and compared with 143 discs in 54 patients in the asymptomatic group. The presence of a high-intensity zone was determined by a standardized criteria on T2-weighted magnetic resonance images. Psychometric testing also was administered to each patient before discography. Standard discography was performed on all the patients, and the pain response was recorded using a visual analog scale according to the Walsh et al criteria.
The prevalence of a high-intensity zone in the patient populations was 59% in the symptomatic group and 24% in the asymptomatic group. In the symptomatic group, 33 (30.2%) of 109 discs were found to have a high-intensity zone. In the asymptomatic group, 13 of 143 discs were found to have a high-intensity zone. In the symptomatic group, 72.7% of the discs with a high-intensity zone were positive on discography, whereas 38.2% of the discs without a high-intensity zone were positive. In the asymptomatic group, 69.2% of the discs with a high-intensity zone were positive on discography, whereas 10% of the discs without a high-intensity zone were positive. In the patients with normal psychometric testing, 50% of the discs with a high-intensity zone were positive on discography, as compared with 100% positive discography results in patients with abnormal psychometric testing or chronic pain.
The presence of a high-intensity zonedoes not reliably indicate the presence of symptomaticinternal disc disruption. Although higher in symptomaticpatients, the prevalence of a high-intensity zone inasymptomatic individuals with degenerative disc disease (25%) is too high for meaningful clinical use. When injected during discography, the same percentage of asymptomatic and symptomatic discs with a high-intensity zone were shown to be painful.
From the Division of Orthopaedic Spine Surgery, Stanford University, Stanford, California.
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Eugene J. Carragee, MD
Director of Orthopaedic Spine Center
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Stanford, CA 94305
Device status category: 1.
Conflict of interest category: 14.