Spine
- 
    
    
Cross-sectional radioanatomical study. ⋯ 3.
 - 
    
    
Retrospective study. ⋯ 3.
 - 
    
    
Retrospective review of prospectively-collected registry data. ⋯ 3.
 - 
    
    
A prospective cohort study. ⋯ 3.
 - 
    
    
Retrospective cohort. ⋯ 3.