Application of the Ames–International Spine Study Group radiographic modifiers to an asymptomatic population: are the thresholds for "normal" appropriate?

The Ames-ISSG classification sagittal modifiers cSVA and TS-CL grade 0 describe normal anatomy. A CBVA grade of 1 is present in 36% of asymptomatic individuals with no difference in HRQOL scores. This study validates the threshold for grade 0 in a normative population for TS-CL and cSVA. It also highlights inconsistency in CBVA and the importance of specific instructions for appropriate evaluation.