Study design: Retrospective monozygotic twin cohort study.
Objectives: Our goal was to investigate the associations between different spinal MRI findings and current, past year, and lifetime low back pain after adjusting for occupational physical loading, smoking, genetics, and early family influences.
Summary of background data: The role of spinal pathology in back symptoms continues to be controversial.
Methods: The study participants consisted of 115 monozygotic male twin pairs 35 to 69 years of age. The qualitatively assessed MRI parameters were as follows: disc height, bulging, herniations, anular tears, osteophytes, spinal stenosis, and endplate changes. Signal intensity was measured quantitatively.
Results: After controlling for age, disc height was associated with all back pain variables studied and anular tears with LBP frequency and intensity during the 12 months before imaging. Both were associated with lifetime frequency of low back pain interfering with daily activities, disability, and intensity of the worst lifetime pain episode. Other MRI findings did not explain the various symptom histories. Adjusting for physical loading in the past 12 months increased the associations of anular tears and "low back pain today" and 12-month low back pain parameters. After controlling for genotype and other familial influences, the within-pair differences in disc height and anular tears accounted for 6% to 12% of the total variance in the within-pair differences of low back pain variables.
Conclusion: These findings raise new questions about the underlying mechanisms of LBP. The sensitivities of the only significant MRI parameters, disc height narrowing and anular tears, are poor, and these findings alone are of limited clinical importance.