The main reason for replacing any arthritic joint with an artificial joint is to stop the bones from rubbing against each other. This rubbing causes pain. Replacing the painful arthritic joint with an artificial joint gives the joint a new surface, which lets it move smoothly without causing pain.
Many operations are used to treat problems in the wrist. A fusion surgery can get rid of pain and restore strength in badly degenerated wrist joints. Fusion surgeries make the wrist strong again, but they greatly reduce the wrist's range of motion. This makes fusion surgery a poor choice for some people.