I have worked in the CCL for over 20 years. I have helped open blocked vessels all over the body with many techniques and devices.
In your case, the details of how the blockage can be opened need to be understood. The doctors may have (and should have) explained what it takes to fix these things.
No matter where the blockage is, if it is done percutaneously, nothing can clear the blockage until a wire can be passed thru the channel (lumen) of the vessel.
If the wire can be passed thru the blockage, below the blockage, and into a normal (undiseased) area of the vessel, then a device can be passed along that wire and to the blockage.
A device could be a balloon, a stent, or a plaque reducing device. These devices have to be able to pass to and thru the blockage over the wire in order to open the blockage.
Even if the wire passes, there is no guarantee a device will pass. The device may be too bulky or the disease too much to get thru. If the device can get thru the blockage, this will open the lumen and allow bloodflow.
I would ask the doctor if they have used a device called The SilverHawk® Plaque Excision System ?
This is a device used to remove plaque that blocks arteries and interrupts blood flow. Unlike other methods of restoring bloodflow, the SilverHawk removes the obstruction – plaque build-up – instead of simply compressing it against the vessel wall.
I have used this device many many times. It is most useful in this very application. It may be that after this device clears the blockage there will also need to be a stent placed to help hold the vessel open.
Key to this process is the size of the blood vessel. We are talking about 1.5mm to 2.5 mm sized vessels---very small. Even with them being opened, the pressure (flow rate) that far down is low and the vessel may close up again.
Many times in these cases, there are what are called "collaterals", blood vessels that form around a blocked main vessel to try to get blood past.
Some doctors feel that if there are adequate collaterals to the area below the knee then there is no use spending time opening the main ones.
Amputation, while difficult to accept, many times it is inevitable in these cases. We try, sometimes for hours, to get these vessels open, only to hear a few months later that the limb just didn't heal.
Hyperbaric therapy may help, also.
Whatever happens, I hope your father finds relief.