Shoulder: Reverse shoulder replacement

This is an example of rotator cuff arthropathy treated with reverse replacement.

The patient presented with a history of remote injury. Xrays above show an abnormal glenohumeral joint, with severe degenerative changes. The patient accordingly had severe symptoms, continuous pain that was so bad - she could not sleep at night.

My first thought was to perform a regular shoulder replacement. She however had absolute inability to raise the arm and an MRI showed a large rotator cuff tear with muscle atrophy.

A regular shoulder replacement prosthesis, in the absence of a functional rotator cuff, would have resulted in proximal migration, dysfunction, and inability to raise the arm. To understand why, it is necessary to remember that a normal shoulder socket - the glenoid - is a rather small and flat surface, it is not a true socket. The rotator cuff is what completes the shoulder joint and what makes the ball of the humerus stay on that shallow glenoid socket.

Under the circumstances, reverse shoulder replacement was the recommended treatment for this patient.

Unlike the regular shoulder replacement operation, in which the surfaces of both the glenoid and the humerus are simply replaced with artificial materials, in a reverse shoulder replacement the positions of the ball and socket are changed: the humerus is fitted with a socket, whereas glenoid is fitted with a sphere. By switching the places, and by creating a deeper ball-and-socket joint, the articulation of the shoulder becomes mechanically more stable and the rotator cuff becomes redundant in a way.

There is no free lunch, however, and motion of the shoulder after a reverse prosthesis is not quite as good as itmight have been with a regular shoulder replacement with intact rotator cuff. For the right patient, however, shoulder function after this operation is much better than before.

Here is the xray the appearance after surgery:

Here is a picture of the same patient, raising her arm up. She is pain free, happy with her artificial shoulder.

Reverse shoulder replacement is not without risks. It is no longer an experimental procedure, but it does not have the track record of, say, hip replacement or knee replacement prostheses. It is an operation that is best reserved for elderly patients, or for extreme cases.

Here are some of the things that can go wrong:

  1. Like every other joint replacement surgery, a reverse shoulder replacement it is susceptible to infection.
  2. Glenoid loosening, notching, fracture are possible.
  3. Dislocation of the artificial joint is a possibility as well.
  4. Delayed acromion fracture is something that sometimes happens after a reverse shoulder replacement. The acromion is where the deltoid muscle attaches, and after a reverse replacement, the deltoid is the only muscle raising the arm up and can sometimes stress the acromion too much.