Arthrodesis is a mainly used in the context for a surgical term for the fusion of two or more bones. Occasionally the joint between two bones become fused naturally causing an arthrodesis. "Arthro" means joint, as in arthritis, the inflammation of a joint. "Desis" is used to described a fusion, or the forming together.
Fusions are joint destroying procedures. It is not used to restore the function of a joint, rather completely destroy the joint to relieve pain, or obtain a structural correction. Typically it is used in patients where the joints have become eroded or destroyed due to underlying disease, as in osteoarthritis, rheumatoid arthritis, and many of the other arthritic processes.
Typically an arthrodesis requires some type of fixation whether plates, screws, or wires to keep these bones positioned till your body heals the bones to become one. Fusions occasionally require a use of a bone graft to aid in the healing.