I feel sad for the conditions like this. As you asked the condition of polio
and the blood supply is not interrelated in any way. Though over time since the requirement of the paralyzed leg is less the blood supply becomes less according to its demand but not to extent to produce wounds. Now coming to the wound part the description suggest a arterial occlusion most likely due to atherosclerotic disease and she has to undergo few tests for locating the site of obstruction. In this case if you elevate the limb there will be further problems. Only solution is to consult a vascular surgeon if the wound dont heal by conservative treatment. To be open there are very few things that can be done at this age. Hope my suggestion helps.Please feel free to ask any further quarries.