Arthrodesis refers to fusion of bones[joints]. In ankle injuries affecting the tarsal bone called TALUS there may resultant loss of viability [avascular necrosis] or complete extrusion of the bone. This means that there will be a gap in the the ankle due to loss of bony tissue which is corrected by fusing two other bones commonly tibia & calcaneum.
There were cases where total talus extrusion treated with the sandwich block. The sandwich block arthrodesis offers a useful alternative for the treatment serious lower extremity injuries
I have not had this surgery but from what I understand, this surgery uses at least two pieces of bone from the patient to repair a certain area. The idea of using the patient's own bone supply is to minimize risks using cadaver bones (ie…infection, rejection, etc…).
I have heard about this type of orthopedic surgery. Though I personally do not have any experience or don't know someone who has had this, I am aware that it is for fusing bones together.