life after surgery
almost 4 years ago I had a lam/diskectomy at l5/s1, it failed and four months later I had a front/rear fusion at l5/s1. That failed also. Life sucks, and I have my good days and my bad, but overall, it is better than is was between the first surgery and the second.
Even if all goes well, I would be very leery of a doctor allowing you to ride before a year has past. Recovery from such an invasive procedure is slow, even when things go well. You may, in many cases, feel great, but that doesn't mean your muscles are back up to snuff and working well again.
I no longer own a horse, so I don't get to go out much, but I have been out since I got hurt, and I can tell you that riding a horse hurts a whole lot less than riding in the car.
I can also tell you, that if you love riding, then you will do it again after-wards. Whether things go extremely well, or poorly, there will come a time when you will need to feel the muscles beneath you and the wind in your face. A time when you need to prove to yourself that you can still do it.
I would recommend now, finding and developing a relationship with someone with an absolutely bombproof horse. You cannot risk a fall after your surgery, at least for a year or two. And after sitting idle for all that time, I doubt your own horse will still be a good choice for that first ride (I could be wrong on that). Going and riding a nice bombproof stable student horse the first few times out could make a huge difference.
The biggest thing I can recommend is keep a positive attitude no matter what happens, and find others with similar problems that you can talk to and work things out with. Back pain is a special thing, other people cannot see or understand your problems, you will go out on good days, and stay in on bad days, because of that, most people who know you will greatly underestimate the issues you have. Talking to others with the same problems can help you from falling into the trap of depression. Riding can also help keep you out of that trap, if you are able.
You didn't say, but I hope that your horse is at your home, or boarded closely. A daily grooming session with your horse for the months you cannot ride, if possible, would be a great way to really latch down and tighten the relationship you have, and also a wonderful therapy exercise for you, doctor permitting of course.
I wish you luck, and hope that things work out well for you. Give me a shout if you think there are some questions I might be able to answer for you or some help I could give.