Pain centralization and lumbar disc MRI findings in chronic low back pain patients
Laslett, M; Kilpikoski, S; Airaksinen, O; Kankaanpää, M; Alen, M
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Background: Centralization of pain is a specific finding in assessing low back pain (LBP). A dynamic, internal "disc model" has been hypothesized as an underlying mechanism for pain centralization, which has shown a high positive correlation with pain during provocation discography. Structural abnormalities on MRI are also common among asymptomatic individuals, but association of centralization among symptomatic individuals to imaged disc pathology has not been evaluated. Aims: To estimate the association (criterion-related validity) of the centralization phenomenon with magnetic resonance imaging (MRI) findings of lumbar disc pathology, as the criterion standard among chronic low back pain patients. Methods: Randomly drawn volunteers (N=39) with non-specific LBP from a larger randomized controlled trial were clinically assessed for the presence of centralization by two physiotherapists using the McKenzie Method. MRI slices of patients' lumbar spines from L1 to S1 levels were acquired with a 1.5 Tesla superconducting magnet. Findings were recorded by an experienced radiologist. Validity was estimated with sensitivity, specificity, positive (PPV) and negative predictive values (NPV) and likelihood ratios. Results: In the total sample, the prevalence of the MRI features most closely associated to pain was 82%, and among centralizers 94%. Sensitivity of centralization was 0.91, specificity 0.5, PPV 0.94; NPV 0.40, positive likelihood ratio 1.8 and negative likelihood ratio -0.18. Conclusion: In this study, MRI showed that pain centralization is associated with abnormalities of lumbar discs. As the centralization phenomenon is closely associated with good treatment outcomes, we recommend centralization guided conservative treatment for disc pathologies before surgical referral.