However, it may lack a validation and reliability study for measurement of T1 slope in MRI. T1 sagittal angle or T1 slope was defined as the angle between a horizontal line and the superior endplate of T1 [234]. However, it was defined and measured in radiography. In this paper T1 slope was measured in MRI when the subject was lying in a prone position, which is different from the position when radiography was taken clinically (normally in a standing or sitting position). Although the relationship between disc degeneration and T1 slope measured in MRI warrants the consistency and integration, T1 slope in MRI is different from the one in radiography regarding several reasons, first the cervical alignment may alter when the subject lied, second the selection of MRI frame is different from the lateral radiography, and third bone structure is preferred to be identified by radiography. Thus, a validation and reliability study is needed for measuring T1 slope in MRI before it is further applied.