This man doctor John R. Christopher was called the father of modern herbology. He had many patients and often make house calls. He developed an incurables program and established the school of natural healing.
In his book, he tells case studies of curing gangrene even amazing the doctors who said amputation was the only option. He later went on to teach Dr. Richard Schulze who taught along side him many years and worked ion dying patients about 20 years in his underground clinic. He intensified Christopher's incurables programs and cured many people who doctors gave no hope to...most should have been dead months ago and can to him only when they had been everywhere else and had no hope.
I believe in Schulze. His program helped me--in fact, I have not seen natural healing fail when it is applied correctly. I know people with cancer who have been cured by the program.
I enclose a page from a website about how Christopher cured gangrene.
If you do it, be sure to use organic or wild crafted (in the wilds) herbs. You can buy them online or at whole foods or wild oats or some health food stores and coops..even just a few spoons which cost only a dollar or so.
If you are taking herbs internally, use tinctures instead of capsules for best absorption.
Other health info is here to but this is the link for the gangrene.
Here is some additional information from Christopher's book Soak limb in marshmallow root tea covering gangrene area w/tea as hot as you can take and leave there long periods of time..soaking works faster than poultice or tea..drinking tea with it helps..plantain (which grows everywhere in parks on lawns--the herb not produce) also helps..pain can be relieved by adding lobelia (small amount)
Another gangrene formula he used is slippery elm i part w/ one part activated charcoal (mix with hot water or with a infusion of Wormwood to paste consistency (charcoal may stain permanently if used on open wounds..If you can find raw milk mix with slippery elm powder and brewing yeast (mix slippery elm and yeast with hot milk (if brewing yeast not available use a yeast cake in warm water and mix..apply over area and cover (with plastic and heating pad over that would be good)
If your grandma can take it, cayenne is often also used (it increases circulation among other things. My mom had infected sores on her legs..I talked her into doing the cayenne (which she did not like of course as it burned) but next day, legs dramatically improved (she did not associate it with the herbs as she doesn't believe in natural healing). I have never seen natural healing fail. I don't know how bad your grandma's leg is but it can be improved or maybe even cured. You may have to up the intensity of the program. You might try to ease into cayenne adding a small amount ot the soaks above or alternate those with the cayenne formentations.
Here is what Dr Schulze uses (but his cayenne is extra hot..I'm not sure if I'd use or not..maybe a different brand??)
As part of his recommendation, he does the incurables program. The save your life video with him and Sam Biser are currently on eBay (current bid $52--originally about $400..well worth it..12 hours). this also contains his incurables program details