The shoulder is a ball-and-socket joint. The end of the upper arm bone (the humeral head) forms the ball, while part of the shoulder blade (the glenoid) forms the socket.
Shoulder replacement surgery replaces the ball and sometimes the socket with man-made parts. There are several types of shoulder replacement surgery:
Hemiarthroplasty is where the ball part of the joint (the humeral head) is replaced with an artificial ball component with a stem that extends into the shaft part of the bone. This is usually used for fractures but is also used in many cases of arthritis.
Shoulder resurfacing is a different type of hemiarthroplasty where, instead of removing the humeral head and replacing it with an artificial ball on a stem, a metal cap is fitted over the ball part of the joint. This means less bone has to be removed during the operation.
Total arthroplasty is where both the ball (of the upper arm) and socket (of the shoulder blade) are replaced. This is increasingly used for very specific kinds of arthritis depending on your age, how badly worn the natural joint is and the state of the tendons around the joint. Occasionally a total arthroplasty will be carried out using a resurfacing component.
Reverse anatomy arthroplasty is where the artificial components are fitted in reverse – that is, the socket to the upper arm bone and the ball to the shoulder blade. Currently this is only used in patients with severe arthritis of the shoulder joint and very poor tendon cover around the joint. It can sometimes be used if a patient has both a severe joint fracture and poor tendon function.
Your surgeon will consider which type of joint replacement will be most suitable for your shoulder problem. They'll discuss this and the possible complications with you, and you'll then have time to think things through before you decide whether to go ahead.
The operation will be carried out using a general anaesthetic (in which case you’ll be asleep) and/or a local anaesthetic (which numbs the nerves to the arm and shoulder). The shoulder joint is normally opened from the front or top and the muscles moved out of the way (retracted). The damaged bone of the humeral head is then removed and the remaining bone is prepared for the artificial component to be fitted.
In elbow replacements both sides of the joint are replaced. The upper arm and forearm components (humeral and ulnar components) are made of both metal and plastic. The operation will be carried out using a general and/or a local anaesthetic. The elbow joint is usually opened from the back and the muscles moved back. The parts of the bone with damaged joint surfaces are then removed and the shafts of the prepared ulna and humerus have the components inserted, which are usually cemented in. Most designs have a hinge or pivot between the two halves.
If the arthritis affects only the radial head then a metal radial head replacement is occasionally used. This leaves the rest of your elbow joint unchanged. This may also be used for some fractures.