Performed by – Ankit Desai, Gareth Hill, Philip Rosell

Shoulder replacement has been an established treatment for many years now with a proven track record in terms of safety, satisfaction and durability. The procedure generally involves the replacement of both the ball joint of the humerus at the shoulder and the replacement of the shoulder socket.

When is it done?
Shoulder replacement is performed for arthritis of the shoulder or after fractures of the shoulder which cannot be repaired. The main reason for surgery in arthritis is to relieve pain but stiffness or loss of movement may also be improved.

Types of shoulder replacement
There are two principal types of shoulder replacement, a conventional or anatomic replacement and a reverse polarity replacement.

In anatomic replacement, the humeral head (ball joint) is replaced with a metal ball joint and a plastic resurfacing is placed on the glenoid socket (on the shoulder blade). This recreates the normal anatomy of the shoulder and is reliant on the rotator cuff muscles working well for its function. This is typically done in younger patients (under 70).

Reverse polarity replacements were developed to be used in patients where the rotator cuff had failed and there was a more significant loss of function as well as pain. In this scenario the normal mechanics of the shoulder are reversed with the ball joint going on the glenoid socket (on the shoulder blade) and the humerus having a plastic socket placed in or on the surface where the ball joint used to be. This changes the centre of rotation of the shoulder and allows the muscles outside the joint like the deltoid to become the principal movers of the arm and shoulder.

Both types of replacement are metal on plastic joints, so there is no risk of metal debris such as occurred with some types of hip replacement. The Implants may be secured with cement, but most are now uncemented with the bone bonding directly to the implants (although a small amount of cement is still used for the anatomic replacements to secure the socket.)

The type of replacement that is suitable for you will be discussed in the outpatient clinic prior to any firm decision on surgery.

Is surgery inevitable?
No – surgery is usually performed to improve pain and quality of life. In some patients this can be managed by physiotherapy and standard painkillers. Other times a nerve block may be offered to switch off the nerve that controls pain in the shoulder (suprascapular nerve). This can improve pain but not usually movement. If these procedures do not provide sufficient relief or the movement is too restrictive then replacement is a good option.

What does surgery involve?
The operation is usually performed under general anaesthetic but you may be offered a nerve block injection as well. The surgery is performed through a short incision at the front of the shoulder. One of the muscles (subscapularis) and the capsule are lifted off the joint and the ball joint is then exposed. The ball joint is then cut off to provide space to get to the socket which will be resurfaced or replaced with the implants decided on for your operation. After replacing the socket, the humeral bone and ball joint is then replaced with either a new ball joint or the stem and socket for the reverse implant.

The muscle and capsule are repaired back to the bone or secured by sutures through the new joint replacement and the skin is then closed, typically with a dissolving suture.

Post-operative recovery
Typically, you will only need to stay in hospital for 1 night after your operation although some will stay for 2 nights if they need more time to recover or if they live alone and need to be a bit more independent.

After surgery you will be placed in a sling for about 4 weeks and then start physiotherapy exercises. You should be able to start strengthening exercises at around 8 weeks by which time you should have movement to at least shoulder height to the front and the side with the ability to get your hand to the top of your head and behind your back for self-care.

You may return to driving when you have sufficient movement which will typically be at around the 6-8 week point.

Outcomes and risks
Shoulder replacement outcomes are generally very good, with over 90% of patients getting significant improvements in pain and movement. The implants have a planning life of 15 years which does mean that they may need to be revised (having a second replacement) if they wear out or become loose.

There is a small risk of infection, and you will be given antibiotics on the day of surgery to keep that risk as low as possible (overall around 1%). If a joint becomes infected it may need more treatment with prolonged antibiotics and further surgery up to and including a revision of the implants.

There is also a low risk of nerve injury with the main nerves to your arm running close to the shoulder. The nerves are sometimes stretched or bruised by retractors (instruments used to hold muscles and tissues out of the surgical field). This is usually temporary and improves after a relatively short period of time although it can be permanent. The risk of this remains very low and is below 1%.

Implants may loosen over time and the muscles and tendons around a conventional anatomic replacement may fail leading to loss of function. In these situations further surgery is usually required.

There is a small risk of a fracture at the time of surgery as the metal implant is placed into the humerus. If this happens it is usually not too much of a problem and your surgeon will be able to address the fracture and complete the operation without compromising the outcome.

All shoulder replacements are monitored on the National Joint Registry. You will be asked to provide your data to this organisation which helps to identify the best practise in joint replacement surgery and the best performing implants.