Spine
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A cross-sectional study. ⋯ 3.
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Retrospective cohort utilizing the National Inpatient Sample (NIS) 2003 to 2014. ⋯ 3.
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A retrospective study, using prospectively collected data. ⋯ 4.
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A retrospective study. ⋯ 4.
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A retrospective, long-term follow-up study. ⋯ 4.