I'm 75 and 3 weeks ago I had a fusion of L-3 and L-4. The injury was 54 years old, and I finally could no longer stand up without a staff to pull me up straight. Walking was very painful, sitting not so much.
I've been very physically strong all my life, even though my body is small. Really tough and quite heavy work, simply because I loved doing it.
Don't be afraid if you have a good surgeon. 3 weeks out, I only have pain from the surgery itself, and it gets less every day. In my right leg, the long nerves to the foot sometimes get pretty numb, and they sometimes burn, but it's not a constant thing. I expect it to go away. I'm walking 1/4 miles per day, and by summer, I expect to do pretty well whatever my old back will do.
My doctor asks that I consume 2500 calories of high protein foods a day --about 90 grams, from high protein drinks, the rest from other foods. The metabolism thriples during the reconstruction of bone. I have a device implanted that inhances bone growth. It was left inside me. It will be active approximately 3 months, and those 3 months are when you want to consume about 10,000 IUs of vitamin D and 1500 mg, of Calcium citrate -- morning and evening.
I was blessed because I was referred to Dr. Myles in Bedford, TX. I didn't know him at all, but he's a wonderfully kind and smart man.
No matter how much pain you can stand, the body does come to a line it cannot cross. Good luck. I personally believe that all healing comes from Above, and a person will be led to do the right thing.