Arthrodesis is fusion of a joint. This is a specific procedure that we typically use as a last resort, but it is used in a few specific instances for primary surgical treatment such as hyperextension injuries of the carpal (wrist) joint.
These particular surgeries can take a long time to heal because you are taking a structure, joint, that typically wants to move and trying to get it to heal and fuse.

The surgery requires removal of the cartilage surfaces and placement of bone graft and then typically placement of a plate and screws. It also requires the placement of external support such as a splint or cast in some cases. It will usually take 10 weeks plus to get these to heal where a typical fracture takes about 8 weeks to heal.