The nonhealing ulcer is primarily due to pressure effect of deformed ankle (lateral malleolus) on the skin. I would be very reluctant to believe that it will ever heal on its own, and the deformation can be corrected conservatively

I would use knee walker to try to heal ulcer. If  has pulses, I would then do tibia to calcaneul fusion with IM rod or external fixator

Thanks

Dear you have a real complicated charcoal foot.  I can see the the strategy for managment is:

1- The apparent cause for the ulcer and deformity with consequent retarded healing is bone factor. so first please thurouhly  exclude other known 5 factors; as blood quality , quantity, associated morbidity (you can revise that here; http://onlinelibrary.wiley.com/doi/10.1111/jdi.12425/abstract

2- when corrected all other factors except the bone factor, inform and explain to the patient that this is a trial to avoid amputation is possible!! and have medico-legal concent that the procedures and operations you are going to do is for limb salvage otherwise amputation is the only way.

3- Prepare the foot and the wound by broad spectrum AB cover including anti Mersa

4- in the OR under fluoroscopic guide do excision of the small completely separated bone segments + try to correct the deformity even by chiselling part of the bone.  then if there is no more infection and the wound is clean, so under cover of antibiotics specially MERSA & anaerobes do fixation to the ankle.  

5- Then according to the situation or remaining bones,   fixation will be  ; by cannulated nails or external fixation 

6- daily care for the wound, supplement to bone matrix which is rarefied, continue antibiotics and you can allow patient to walk in the room for a month, till radiological evidence of starting bone healing and fixation

7- Inform the patient that this procedure can be repeated 

Best Regards