I Had A Cervical Fusion From A Car Accident In

I had a cervical fusion from a car accident in my 30's and now I am 61. My Dr.told me I have compressed vertebrae . My fusion was c4 through c7. 9 months after surgery I had a disability of 33 and a third permanent and progressive. I don't understand what exactly that means. I know that my pain and use of legs and arms are significantly weaker now. Can you explain what is happening?