I had a spinal fusion 10 and a half months ago and had to quit before it. I was told that smoking (don't know which chemicals exactly are the culprit, obviously alot of bad stuff in cigarettes) deprives your bones of oxygen, nutrients, and minerals--just like smoking does to other organs and tissues in the body.
The oxygen and nutrients and minerals are supplied to your bones by the blood stream and smoking elevates the levels of nicotine in your blood and causes the blood vessels to constrict.
Nicotine constricts blood vessels a certain percentage of their normal diameter. Because of the constriction of the vessels, decreased levels of nutrients are supplied to the bones.
I was told that this is the reason why the bones do not heal well for smokers after fusion.
I am not sure of alternatives for smoking such as e-cigs and all--I went cold turkey, had the surgery, and haven't had a smoke for 10 and 1/2 months.
I know it's awful to have to quit this way and I am sorry you have to have such a surgery on your foot. I wish you much luck with your surgery and with quitting smoking.
Take care and post on how you make out.