Shoulder replacement is required when the shoulder joint is damaged beyond repair. There are two main reasons for this damage – one is severe fracture, breaking the ball of the shoulder into several pieces, and the other is damage as a result of arthritis.
Shoulder is a ball and socket joint. In cases of damage to the ball alone, replacing only the ball may be sufficient (hemi-arthroplasty). In cases where both, the ball and the socket are damaged, both may need to be replaced. There are cases of arthritis, where the surface of the ball is shaved off and replaced by a shell of steel (resurfacing).
Shoulder replacement is done via a 5 inch incision in front of the shoulder. After reaching the damaged ball and socket, the damaged ball is sawed off. The socket is cleaned with the help of special trimming tools called reamers. An artificial cup, made of plastic is fixed with the help of bone cement, on top of the patients damaged cup. Next the cannal in the arm bone is opened and space created for taking the artificial ball which has a stem to fix it to the parent bone. The muscle around are re-sutured. With currently available techniques and implants, shoulder replacement is rivaling the success of knee replacement.
The most advance version of shoulder replacement is what is called reverse shoulder replacement. In this, the ball and socket arrangement of the shoulder is reversed, that is, the ball is fixed on the cup side and the cup on the ball side. This type of shoulder replacement is meant for special situations where there is severe damage to the muscles around the shoulder as well. In such extreme shoulders ordinally shoulder replacement would be unsuccessful.