General information
The inverse shoulder prosthesis refers to a form of shoulder joint replacement that does not correspond to the anatomical shape. This type of prosthesis is used when the shoulder muscles are no longer functional and the shoulder joint is degeneratively altered. The operation offers the possibility of pain relief and restores part of the function.
A major disadvantage is a possible revision operation after a few years, which may result in a loss of function of the shoulder joint. The term “inverse shoulder prosthesis” refers to a prosthesis that is constructed in the opposite way to the normal shoulder joint. Anatomically correct, the head of the joint sits on the humerus, the socket lies on the acromioclavicular joint. With the inverse shoulder prosthesis, the head of the joint is now placed in the place of the bony socket, and the artificial socket sits on the upper arm.
Who benefits from an inverse shoulder prosthesis?
A shoulder prosthesis is always necessary if the patient concerned suffers from one of the following diseases: An inverse shoulder prosthesis is particularly beneficial if, in addition to these conditions, there is also pronounced damage to the shoulder joint stabilizing muscles (rotator cuff).
- Advanced shoulder joint arthrosis
- Rheumatic disease
- A joint infection (omarthritis)
- Chronic shoulder joint instability (shoulder luxation)
- At fractures in the joint surface or a humeral head necrosis
Reasons for surgery
The inverse shoulder prosthesis is used when there is wear and tear on the joint, making an artificial joint necessary. At the same time, the muscles of the rotator cuff must be inoperative, so that a normal shoulder prosthesis would fail. The inverse shoulder prosthesis is also used in cases of accidents and comminuted fractures of the humeral head or in cases of dislocations of the shoulder that have existed for years.
This inverse construction of the shoulder joint changes the biomechanics of the shoulder. Normally, several muscles, the so-called rotator cuff, must contract to move the shoulder. However, the inverse construction shifts the center of rotation of the shoulder downwards and inwards. As a result, the patient is now only dependent on one functioning muscle to use the prosthesis. This is the deltoid muscle, which is not part of the rotator cuff.
