There are different types of shoulder prostheses. The surgeon will decide which type is most suitable for you based on the clinical examination, functional evaluation and imaging (CT scan). He will then discuss these findings with you, as well as the expected advantages and disadvantages.
Anatomical shoulder arthroplasty (ASA)
For this type of prosthesis, it is possible to replace only the head or both the head and the socket of the shoulder joint. The requirement for this type of prosthesis is that the tendons of the shoulder muscles are in good condition.
- In a total shoulder replacement (TSA), both a new head and a new socket are placed. A total shoulder replacement is performed when both parts of the joint are worn out (and when the muscles and tendons are still in good condition). The ball and socket of the joint receive a new covering that replaces the worn-out cartilage. The head is made of metal (cobalt-chromium), the socket is replaced by a disc in hard plastic (polyethylene). This procedure is performed less frequently (25% of shoulder replacements) because the tendons must be in good condition, and because this prosthesis must be performed with great precision (a few degrees and millimeters make a big difference), which requires great experience on the part of the surgeon. Because no tendon is cut during surgery, rehabilitation is quick and easy. No support bandage is needed. This procedure is very reliable for the improvement of pain and mobility. Most people can use the arm above the head, at the back of the head, and behind the back again after the operation. Daily activities can be performed independently again. However, there is a risk of stiffness, especially in the case of limited exercise. Heavy work or shock loading should be avoided to prevent premature wear and tear of the prosthesis. The lifespan of a shoulder prosthesis is 15 to 20 years and depends mainly on the risk of loosening the socket. Therefore, in the case of young people, placement of a new socket will usually be discouraged (cfr further).
ADD PHOTO (Femke)
- The half prosthesis (hemiprosthesis) is used when only the shoulder head is affected but not the socket. The head is replaced by a ball made of plastic (pyrocarbon), which is attached to the shaft of the upper arm with a stem(s). This type of prosthesis can also be used for fractures, in which case pieces of bone, together with the tendons, are attached to the prosthesis with strong wires (if the bones are sufficiently strong (< 65 y). Normally, no tendons are cut when this prosthesis is inserted, allowing rehabilitation to start immediately. This prosthesis is very appealing for younger patients (<45 y) because a longer life of the prosthesis is achieved (no risk of plastic bowl loosening). However, pain may persist for some patients because the polycarbonate head rubs against the surface of the socket. Regular follow-up with radiological monitoring is necessary.
ADD PHOTO (Femke)
Reversed shoulder arthroplasty (RSA).
When shoulder abrasion occurs due to irreparable tearing of the shoulder tendons, it is called ‘rotator cuff arthropathy’. Since the tendons are torn, an anatomical prosthesis cannot provide function improvement. An inverted shoulder prosthesis can. In this prosthesis, a head is placed on the original socket and a socket is placed where the head used to be. This is also why it is called a ‘reversed’ prosthesis as the function of the head and socket are reversed. This turns the shoulder into a more stable “hinge-type” joint. The hinge point moves inwards, increasing the strength arm of the muscles. The large deltoid muscle comes under more tension, allowing it to partly take over the function of the torn tendons. It is also this deltoid muscle that ensures immediate stability of the prosthetic shoulder joint.
This (newer) type of shoulder prosthesis, if placed correctly, guarantees a long lifespan (at least 15 years) so that younger people can also be taken into consideration. This type of prosthesis also allows quick and easy rehabilitation. No sling is fitted because immobilisation of the shoulder is not required. Rehabilitation can start the day after surgery. After rehabilitation, most patients regain most of their shoulder function, including upper arm function. Sometimes, however, the strength to reach with the hand behind the back and/or the strength to turn the arm outward remains limited.
Revision or post-traumatic reverse shoulder replacement
Even if you already have a prosthesis or have a badly healed fracture at the shoulder level, you are eligible for a ‘revision prosthesis’. The doctor will first diagnose a “failed prosthesis” based on objective criteria. Important criteria are sleep-disrupting pain and poor function (stiff joint). An inverted shoulder prosthesis is also frequently performed immediately after severe trauma with a fractured shoulder head (e.g. after fall) when the bone is weak and the tendons are bad. Usually, rehabilitation can also start the day after surgery. If you have received a revision prosthesis, you can still obtain an acceptably good function. However, the risk of complications is greater than with a primary prosthesis. There is a greater chance of luxation of the prosthesis.