Spine
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Retrospective database study based on prospectively collected data. ⋯ 3.
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Retrospective case-control study. ⋯ 4.
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Trajectories of Disability and Low Back Pain Impact: 2-year Follow-up of the Groningen Spine Cohort.
Prospective cohort study. ⋯ 2.
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Prospective study. ⋯ 2.