grandprixer, I haven’t had this fusion surgery and I have a few years (well more than just a few) on you but wanted to share a few thoughts.
A good friend of mine, when I was talking to her about my progressing scoliosis and increasing pain, told me that surgeries such as this are elective. You can elect to do it or not. You might, at this point in your life, choose not to. At some point, the pain and quality of life may be such that you decide you do want to do the surgery. Only you will know when you reach this point.
My take is not as much could you ride but should you ride and the risk if you do come off.
I would start by taking riding out of the equation for a moment. How much pain are you in? Are you willing to assume the risk that surgery may or may not help? It is a cr*p shoot and definitely not an easy choice. I know my surgery didn’t have the outcome I dreamed of but in many ways it was still a win as I am now pain free.
I get the feeling that riding is important to you. I’d be asking the Drs about the risk to your fusion if you do come off the horse you are riding. Damaging the cervical spinal cord can be pretty devastating as I am sure you already know. Would this be a risk you want to take? Any rider can come off any horse at any time
Maybe driving is an alternative to riding? What riding discipline do you participate in now? How do your parents feel about you getting the surgery and riding afterwards?