Spine
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A case-control study. ⋯ 4.
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Retrospective review. ⋯ 3.
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A retrospective study. ⋯ 4.
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Retrospective cohort study of a nationwide database. ⋯ 4.
A case-control study. ⋯ 4.
Retrospective review. ⋯ 3.
A retrospective study. ⋯ 4.
Retrospective cohort study of a nationwide database. ⋯ 4.