Non-repairable rupture of the tendons of the shoulder: the reverse prosthesis
When the rupture of the tendons of the shoulder (rotator cuff) is not repairable, or the shoulder is arthritic, it is sometimes necessary to resort to the establishment of a "reversed" prosthesis.
Below are images of a right shoulder where the rotator cuff tendons are irreparably torn and beyond repair in a 79-year-old man. He can no longer raise his right arm.
Almost completely relieves preoperative pain.
left: MRI: the arrow shows the remains of the torn tendons
on the right: the arrow indicates the extremity of the acromion, a bony point which comes from the scapula, which has gradually worn down the tendons throughout the patient's life, ending in a tear by wear.
When the rotator cuff is irreparably torn, the deltoid muscle, which forms the outer contour of the shoulder, no longer manages to start shoulder elevation on its own. Patients must use the other hand to raise the arm, and to lower it. The head of the humerus is no longer lowered by the rotator cuff at the start of the elevation, and bumps against the acromion, as in the diagram below:
These phenomena cause discomfort and pain.
The reverse prosthesis acts on the biomechanics of the shoulder: below, on the left, we can see the normal anatomical situation, with an intact rotator cuff. The lever arm for deltoid strength is relatively small, but thanks to the rotator cuff, the muscle does a good job of doing its job.
In the reverse prosthesis, the natural "ball" of the humeral head is replaced by a "funnel", and the natural funnel of the scapula by a ball, as shown below on the right. This has the effect of considerably increasing the length of the lever arm, and the deltoid is able to function again, this time without the aid of the cap. The center of rotation of the shoulder is moved inwards.
X-ray result below: we cannot see the half-sphere of the scapula because it is made of polyethylene (specialized plastic), which is transparent to X-rays.
The operation is done by a lateral incision in the shoulder, in a semi-sitting position and in complete narcosis (general anaesthesia): totally painless before the operation.
Elle dure environ 2 heures. La rééducation débute le lendemain de l'intervention, par de la mobilisation passive (sans action musculaire de votre part) par le physiothérapeute. Effet secondaire de l'opération: il reste un petit creux juste en-dessous de la clavicule, là où se trouvait auparavant la tête de l'humerus. Ce n'est pas gênant. Après un séjour hospitalier de 3 à 7 jours, la physiothérapie se poursuit ambulatoirement , généralement pendant 2 à 3 mois.
En résumé, cette opération permet, dans les cas de rupture irréparable de la coiffe des rotateurs, de retrouver une bonne mobilité utile de l'épaule, et soulage presque totalement les douleurs d'avant l'opération.
Ci-dessous, avec un bon travail en physiothérapie, on peut obtenir une bonne mobilité avec une prothèse inversée:
