If it is the L5S1 or L4L5 I can give you some tips.
I had motorcycle accident 9 years ago and had fusion of that area.
First thing on my mind after that was regaining full mobility of my left leg. After that was rehab excercises and all that fun stuff.
After 8 months of this and no weights I was finally given the clearance to train. First workout was so funny, just using the bar and testing to see what where the motions that I could do.
first year was only foccusing on regaining my lower back endurance and mental confidence. Took 4 days of the week only on low back specialization. Hypers, leg raises, side raises, all strenghtening and endurance for the core were mandatory. The imbalance was very noticeable plus sometimes inflamation. Had to take NSAID’s.
After I year on free weights for low back and machines for everything else I moved slowly into free weight territory.
Squats and DL had to be modified and in some instances certain protocols removed from my repertoire. For example I am ok doing full ATG squats, but 90degrees I can not even handle.
DL from the floor, next day bedridden. Half-way from the shins, golden point! see what I mean?
at the 2nd year mark I could squat and deadlift but no standing OHP. Still to this day for some reason the OHP standing can not do. 90 degree seated even worst. Shoulder’s focussed on more volume via raises and use of pre-exhaust.
Basically pre-exhaust and volume become your friend. You can get a fairly sized body, but herculean weights…you run the risk!
Hope it helps