Modern fusion methods have improved the results quite a bit. Nonunion is still a problem for about 10 percent of the patients. The bone simply doesn't fuse completely. Most nonunions are painful. Another operation may be needed to use bone graft to get a solid fusion.

Getting the right position can be a problem. The shoulder must be fused in a position that allows the patient some motion. Not enough flexion may keep the patient from reaching the face to wash or brush teeth. There needs to be the right combination of flexion, rotation, and abduction (moving the arm away from the body).

Sometimes there are problems where the metal plates and screws on the inside rub against bone or soft tissue. The fixation devices can even poke through the skin. If the fusion is solid then part or all of the hardware can be removed.

The last problem is fracture. Without motion the bones around the shoulder start to lose density or mass. This weakens the bone so that even minor trauma can cause a fracture.

All in all shoulder fusion called arthrodesis works well for many patients. It stabilizes the arm and reduces painful symptoms. There's still enough motion to allow for daily activities of care.