1. No infection
2. Make sure there is proper blood flow
3. Offloading of the area
4. Proper debridement and dressing of the wound
Antibiotics alone will probably not heal the area. wounds can heal very quickly or take years. There is a lot of new technology that will help such area Skin substitute grafts, Laser treatments, Ultramist therapy and Hyperbaric oxygen treatments. It is important to treat a wound ASAP so it does not become a chronic area that can develop infection leading to gangrene.
If the wound is not healing, it would be best to follow through with a wound care specialists to determine what other factors are playing a roll in your grandfather's chronic wound.