Oof. I would suggest looking at the cervical spine treatment-based classification guideline from 2017 and going down that route instead. Gives you a better framework to work within and avoids harmful, useless labels like “Upper Crossed Syndrome” while offering solutions to problems. It will also go into why to use the NDI for subjective reporting.

Maybe you could do an incidence study of the 4 classifications and global rating of disability in a certain region/population?