Hi Joanie, and welcome to the board!
Did your doctor give you any permanent lifting restrictions? I have a T4-sacrum fusion and am a meraber of a gym. I look at it as PT. I walk on the treadmill for about 1/2 hour, my top speed being other people's warm up speed and I hold on for dear life, but it's still good exercise. I have found 7 other machines that I use regularly. There are a few others I could use, but they're very similar to the ones I already use. I avoid anything that puts weight on my spine. I pull and push weight, pull down weight, and use the abdominal machine. I do the leg machine and the bicep and tricep machines. I get a good, sweaty workout, but I put little stress on my back.
If in doubt, clear it with your doctor first. But if you're careful and use common sense, you should be fine.
Glad you're able to get out and get your muscles strong! That's the best thing you can do for your back!
Emily