What is a shoulder replacement?
A shoulder replacement is when the joint surface of the shoulder is replaced by artificial bearings. People may have heard of a total hip replacement or total knee replacement, a shoulder replacement is similar. The ball of the shoulder is replaced with a new ball and the socket of the shoulder is replaced with a new socket and these two bearings glide upon each other to lubricate and protect the bones from rubbing against each other, thus usually giving more movement and certainly less pain.
What types of shoulder replacements are there?
There are numerous types of shoulder replacements and brands, but it comes down to two main varieties. One is a standard anatomic shoulder replacement which is done when the bones and tendons around the shoulder are of sufficient quality to allow a replacement based upon normal anatomy. In this scenario when there is bone rubbing on bone, the ball is replaced with an artificial ball and the socket is replaced with a plastic socket. These days the more common socket is one that is cemented into the bone. These are not dissimilar to the sort of design as a total hip replacement, however while the original designs would have looked very similar to a total hip replacement, the new varieties have evolved so much that they have become very shoulder specific. As in all standard shoulder replacements, the risks include the implants loosening with time.
How does a reverse shoulder replacement differ from an anatomic shoulder replacement?
The reverse shoulder replacement is designed for those situations in which the tendons supporting the shoulder are deficient. This is known as a rotator cuff tear. If a rotator cuff tear is small then this is often ignored and an anatomic shoulder replacement is used but in those where there is significant deficiency minor subluxation leads to excess stresses being placed on the shoulder such that an Anatomic shoulder replacement would loosen prematurely. With a deficient rotator cuff, the Anatomic shoulder replacement would not function well, and in these scenarios a reverse shoulder replacement is employed.
A reverse shoulder replacement, as the name suggests, is where the implants are reversed; the ball is placed where the socket is and the socket is placed where the ball is. This leads to an unusual looking x-ray and certainly is a unique design.
The initial concept was developed in France over thirty years ago but has only been well adopted over the last fifteen years.
Initial scepticism regarding how well such implants would work, and the implant last for, has been allayed as these implants are looking to actually perform very well and have quite good longevity. It is now the most common style of shoulder replacement performed in Australia.
The Arthroplasty Register, of which the shoulder forms a subset, incorporates eight year results of shoulder replacements and it transpires that the actual longevity for both standard and reverse shoulder replacements is looking at approximately a 5% revision rate over eight years. This means that one in twenty have had to have further surgery. In fact, the reverse shoulder replacement has slightly better results than the anatomic one, although the reasons for this may rely on the fact that traditionally the reverse shoulder replacement is done in an older patient age group.
Are the protocols any different for reverse or anatomic shoulder replacement?
No, they are not. Both shoulder replacements are done through the same incision, both rely on releasing and then repairing the anterior musculature at the end of the procedure, and it is this that limits the motion one can put on the arm for the first four to six week period following surgery, so as to protect the repair. Both types of replacements require physiotherapy after surgery.
In what other circumstances can a shoulder replacement be incorporated?
Shoulder replacements have always been available for arthritis, however traditionally in those patients who have fractured their shoulder in such a way that the anatomy cannot be restored appropriately, shoulder replacements have been incorporated. Traditionally this has been in the form of a hemiarthroplasty (replacing the humeral bone to restore the shape of the ball). But, as is often the case with fractures of the shoulder, the attachments of the tendons to the proximal bone are often disintegrated and as such the healing potential of these fragments is often poor, especially in patients who often are not in the best of health. As such, in the past a hemiarthroplasty (half a shoulder replacement) has traditionally had poor outcomes in that the movement has been sub-optimal. Over the last ten to fifteen years people have increasingly used reverse shoulder replacements for such fractures, which do not require these tendons and bone to be healed, ie if the tendons and fragments don’t heal correctly the shoulder replacement can still function well.
As such patients with shoulder fractures have actually done very well following reverse shoulder replacements and consequently this is a good indication. That being the case, if the tendons can heal the patient can do that much better and consequently, the rehabilitation after such surgery is slower than in arthritic shoulders, in an attempt to get the tendons to heal to the bone. Therefore the patient is protected in a sling for six weeks, doing gentle range of motion before allowing more movement.
What are the risks of a shoulder replacement of either type?
Most importantly, it is a procedure which requires an anaesthetic for several hours and (to help take the stress off the body) often a nerve block is performed by the anaesthetist to numb the arm. There are risks associated with a block, which the anaesthetist will go into including the sensation of a numb arm for up to twenty-four hours.
Other risks include those of the anaesthetic, including chest infections, urinary tract infections, and of cerebral and cardiac events, the latter of which are extremely rare but need to be taken into consideration. The risks of the procedure itself are the risk of infection and as such the procedure is undertaken using special isolation suits to reduce the risk, as well as using antibiotic cover. As noted above there is a risk of loosening, dislocation (which is rare), nerve paralysis and for the anatomic shoulder replacement, tendon rupture.
Despite all of the risks, shoulder replacements of both varieties are proving to be a good option for those patients struggling with pain.
Contact our friendly team at Glenelg Orthopaedics today for more information on shoulder replacements.